Parasitology-IV

 

Parasitology-IV

 

 

Protozoology

 

Protozoology is that branch of biological science, which deals with unicellular animal life known as protozoa. The history of protozoa dates back to 1674, when Dutch naturalist, Leeuwenhoek, describe them as animalcules. The term protozoa was applied them by Goldfuss 1920.

 

Morphology of the protozoa: All protozoa consists eukaryotic type of cell. Body of the protozoa consists two part i.e., nucleus and cytoplasm.

Nucleus:. Most of the protozoan consist a single nucleus, which is known as vesicular nucleus. But in some, such as B. coli there are two nuclei. In this case one is small in size is known as micronucleus or vesicular nucleus. This is similar to vesicular nucleus of the uninucleated protozoa, performs the function of reproduction. The second large in size is known as meganucleus or macronucleus or massive nucleus. This is usually kidney shaped and it performs the metabolic function of protozoa. Opalina is a multinucleated and consist about two to hundred similar sized nuclei. Other different character of vesicular nucleus, a clear nuclear membrane is present and at the center there is a nucleolus generally called karyosome. In case of mega or massive nucleus large number of chromatic granules are scattered through out the nucleoplasm.

Cytoplasm: It is extra-nuclear part of the protozoa. This is again divided into two parts outer homogenous ectoplasm and inner granular endoplasm. The endoplasma contain food vacuoles and pigmented granules. In non parasitic protozoa there is specific organelles known as contractile vacuole which is responsible for excretion of waste materials. But in most of the parasitic protozoa it is absence. The ectoplasm is homogenous and sometimes protected by thin cuticle structure known as pellicle.

Locomotion of protozoa: The protozoa may move either by gliding or by means of locomotory organelles. Gliding movement is seen in case of Toxoplasma and Sarcocystis. They do not have any locomotory organelles, on the body surface there are numerous ridge like structure which are known as microtubules which help in gliding movement. But other protozoan can move with the help of different types of locomotory organs such as pseudopodia, flagella and cilia. 

Pseudopodia: The pseudopodia are finger like projections (Temporary finger like projections). These are produced only at the time of requirement. This types of organelles are found in amoeba.

Flagella: These are filamentous structure, very fine and highly mobile in nature. Each flagellum consists of a central axial rod known as axoneme, which is surrounded by a cytoplasmic sheath. The axoneme arises from a structure known as kinetoplast, which consists of a nucleus or chromatin mass known as kinetonucleus or parabasal body. Near this kinetoplast another granular substance is present known as blepheroplast or basal granule.

In some protozoa the flagellum runs the side of the body and attached to the body by means of delicate membrane known as undulating membrane.

Cilia: These are also very fine short and small hairs like structure. They arise from the ectoplasm. They are more in number and coverers entire body of the ciliate protozoa. A part from movement they also help in the ingestion of food materials and other function such as required in reproduction.

Nutrition of protozoa: In case of amoeba the food materials are engulfs by means of pseudopodia. In case of B. coli there is special opening known as cytostome which acts as the mouth and food material are taken through this cytostome. In case of Apicomplexa or sporozoa protozoan there is special opening towards the side of anterior part of the body known as micropore or micropyle through which the food materials are taken. In other protozoan food materials are absorbed through the body surface. In all protozoan these food materials enter into a vacuole in which digestion takes place. In B. coli and E. histolytica they used host cells as a food material and in case of E. coli the food material is absorbed through the host intestine.

Types of nutrition: There are mainly two broad type of nutrition is present.

1. Holozoic nutrition: In case of parasitic and commensal protozoa ready made or preformed food material derived from the body of the host.

2. Holophytic nutrition: In this case food is synthesized with the help of chlorophylls carried on the chromatophore in sunlight.

The holozoic nutrition is again divided into number of types.

a. Saprozoic nutrition: This is absorbed nutrient through the body wall, these being utilized directly by the organisms.

b. Coprozoic nutrition: In this case the protozoan takes organic food from the faeces.

Parasitic nutrition:- This type of nutrition only found in protozoan parasites.

Respiration: Most of the protozoa absorb oxygen through the body surface and leave corbondioxide through the respiratory vacuole.

Excretion: The waste materials are excreted through the contractile vacuole in case of freeliving or none parasitic protozoa. In case of parasitic protozoa such as B.coli a spiral opening is present which is known as cytopyge through which the waste materials are excreted. In other parasitic protozoa the waste materials are excreted as small vacuole containing fluid these vacuole come out through the body surface. Parasite not only eats but also drink. It takes fluids into small vacuoles even when it is not feed.  This method of ingestion is known as pinocytosis.

Reproduction: Reproduction in parasitic protozoan usually occurs by two methods

1. Asexual and 2. Sexual.

1. Asexual reproduction is divided into number of types.

a. Binary fission: Binary fission is the commonest form of asexual reproduction. In this two daughter cells result from a parent cell, in most of the protozoa division takes place along the longitudinal axis known as longitudinal binary fission. But in ciliates like B. coli division is along the transverse axis. In this case the nucleus divide first then cytoplasmic division takes place.

b. Multiple fission or schizogony: In this case from one individual more than two individuals are produced. These are occurs by the mitotically division of nucleus in number of small fragment. Each fragment surrounded by a portion of the cytoplasm. The division form is known as a schizont and the daughter form is known as merozoites. The process of the division of nucleus up to the formation of merozoites is known as schizogony.

c. Budding: It is an asexual reproductive process in which two or many daughter forms are produced by the parent cell. There is usually an unequal fragmentation of the nucleus and cytoplasm, but the budded forms are separated off and then developed to full size.

d. Endopolyogeny: It is a form of asexual multiplication or internal budding, where by new progeny are formed within the parent cell. e.g. Toxoplasma, Sarcocystis etc.

e. Endodyogeny: It is a simple form of endopolyogeny in which division occurs in side the mother individual i.e. two daughter individual are formed inside the mother cell later they are separated from the mother cell. It is seen in forms such as Toxoplasma and Sarcocystis.

f. Sporogony: This is an asexual process of multiple fission after sexual reproduction or after syngamy. In this division first of all normally follows syngamy and a number of or very many, sporozoites are formed within the walls of a cyst.

2. Sexual division:

a. Conjugation: It is a form of sexual reproduction, which occurs in the ciliates. In this, two organisms are paired and exchange their nuclear material. The individuals separate and nuclear reorganization takes place. e.g., B. coli

b. Syngamy: It is a sexual reproduction in which two gametes are fuse to form a zygote. The male gamete is a microgamete and the female is called macrogamete, which are produced from microgametocytes or microgamonts and macrogametocytes or macrogamonts, respectively. The process of gamete formation is gametogony and the gametes may be similar in size i.e., called isogamy or may markedly differ called anisogamy.

 

some common term used in protozology:

1. Trophozoite: This is the vegetative form of protozoa, which feeds, grows and ultimately divided to form daughter individual, which repeat the same process.

2. Cyst : It is the immotile form of protozoa which are protected by a cyst wall. The encystation may occur before or after fertilization and they may be transmitted from one individual to other without multiplication e.g., cyst of E. histolitica, Giardia and oocyst of coccidia.

3. Spores: These are the multinucleated form, developed inside the encysted zygote during a process known as sporogony these are called spore which produce sporozoites e.g., coccidia

 

 

 

 

 

 

 

Family: Endamoebidae

Genus: Entamoeba

Species: histolytica and coli

 

Location and host: It is found in the caecum and colon of man, pig, dog, cat, monkey and sometime rat etc. The disease causes by this protozoa is called amoebic dysentery or amoebiasis.

Morphology: It is found in two forms first is trophozoite or vegetative and second is cystic form.

Structure of trophozoite: These are active form and found as two varieties such as large and small. Large forms are more pathogenic and size is more than 20-30 µm in diameter. They have a crawling type of movement with the help of pseudopodia. These vegetative forms sometime passed out in the dysenteric stool.

The cytoplasm has clear ectoplasm and endoplasm. The endoplasm has food vacuole, which is containing host cell, RBC and some time bacteria. The nucleus is single, spherical with an endosome or nucleolus present in the center. The nucleus membrane is lined by a row of fine chromatin granules.

Morphology of cyst form- The cyst are spherical or subspherical in shape and seize is 5-20µm in diameter. These cysts have a double layer cyst wall and these cysts are passed out in constipated stool. The immature stage contains 1. 1-2 nuclei, 2. glycogen granules and 3. chromatoid rod. This glycogen granule and chromatoid rods act as reserve food material. The mature cyst has four nuclei and diffuse glycogen granule but no chromatoid rod. Some cases they disappear when they are consumed.

 

 

 

 

 

 

 

 

 

Life cycle: The cysts that are passed out in faeces or when the uninucleated cyst form is passed out and they grow in mature cyst. When these cysts are ingested by the host with  contaminated food and water then the host is infected. In the intestine some more nuclear division and cytoplasmic division takes place and four nuclei form then eight nucleated form are formed, on rupture of cyst wall, these individuals having uninucleated bodies come out and these are known as amoebulae. They further pass in large intestine and developed in trophozoite.

Multiplication: The larger trophozoites which are more pathogenic, multiply by binary fission and penetrates into the wall of large intestine by means of pseudopodia and these cyst formation also takes place. Before the cyst formation the trophozoites changed into smaller form and expelled out all the food vacuole. They become rounded up and stoped feed, immature stage has 1-2 nuclei and mature cyst have four nuclei after division.

Pathogenicity and symptoms: Large varieties of E. histolytica are more pathogenic. After being excysted in the intestine they penetrates into the intestinal mucosa of large intestine by dissolving the surface (mucosa, submucosa) epithelium with the help of proteolytic enzyme, trypsin and pepdin. They penetrate into the intestinal mucosa to form colonies which penetrate further deep into the submucosa and spread due to this fast spreading flask shape ulcers are produced withy narrow end directed towards the lumen. Sometime they penetrate deep in muscularis mucosa of large intestine and reach lymphatic vessel and blood vessel. Then they are carries to different soft organ of the body inside which they form the ulcer mainly right lobe of the liver is affected. Other organ such as lungs and brain may also be affected.

Symptoms: From the pathogenesis it is known that there are two types of disease 1. intestinal forms and 2. Extra-intestinal forms

Intestinal form: It may be of two types

a. Acute and b. Chronic

Acute: Symptoms 1. Dysentery 2. Abdominal pain, 3. Nausea and vomiting 4. Loss of appetite,  5. Stool may be mixed with blood and mucus 6. There is rectal pain and some time fever is seen.

Chronic form: Any type of symptoms may be seen such as 1. abdominal pain 2. intestinal ulcer 3. headache 4. nausea and vomiting 5. there is bowel irregularity.

Extraintestinal form: The abscesses of liver may produce pain in the liver, lesion may be more in case of right side of liver. There is high fever and the leucocytes count increases, some time liver, brain, lung and rarely abscess are also found.

Diagnosis: 1. By examine the faecal sample, by finding the cyst or trophozoites. For this purpose 1-2% iodine solution, containing solution of iodine and 1% KI is put into the smear and then examine under the microscope. Iodine solution stains the nucleus.  

2. From the clinical symptoms.

3. In chronic case faecal culture may be done in which amoeba develop in the culture.

4. Liver abscess detected from X-ray.

5. Blood sample examination reveals high leukocyte count.

6. There are serological methods such as complement fixation test.

Treatment:

For intestinal form:

a. The drug of choice is metronidazole-400mg every eight hour for 5days in chronic cases in human and 800mg every eight hours for 5days in acute cases in human.

20mg /kg /day for 10days in animals

b. Niridazole - 25mg/kg daily for 5-10 days in adult human.

For extraintestinal form:

a. Emetine hydrochloride- 65mg dissolved in 1ml of distills water and provided deep I/m or s/c injection for 5-10 days in human and dog.

b. Chloroquine - 300mg once daily orally for 5days in human and animal.

Control:

1. Good sanitation.

2. Improved sewage disposal.

3. Avoid contamination of faecal material in the food material.

4. Improvement of personal hygiene.

Amoebiasis is a primary disease of man, although the parasite are found in domesticate animal, they get this infection from human faeces and clinical type of infection is rarely seen in domesticated animal.

 

E. coli

 

It is non-pathogenic amoeba found in the caecum and colon of man and other animals. It is world-wide in distribution being common in warm, moist climates. The morphological character to different from the E. histolytica is given in table below.

 

S.No	Characters	E. histolytica	E. coli
1	Vegetative form or Trophozoite form	20-30µm	20-40µm
2	Motility	active & progressive	sluggish & non progressive movement
3	Inclusion in the food vacuole	Only RBC in fresh specimen	Bacteria are present
4	Nucleolus	Situated at the central of nucleus (Eccentric)	Exocentric
5	Nuclear membrane	Inner surface of it is lined by row of fine chromatin granules	Lined by coarse chromatin granules.
	Cystic form
1	Size	5-20 µm	15-30µm
2	Shape	Spherical	Spherical
3	Cytoplasm	Greenish yellow	Yellow brown
4.	Chromatoid rod	Thick rod like with rounded ends	Filamentous with pointed or square shape.
5	Nuclei	4 nuclei in mature cyst	8 nuclei in mature cyst
6	Nucleolus	Centrally present	Exocentric

 

E. gingivalis

These are found in the gums of man, dog, cat, and monkey etc. They sometime cause pyorrhoea. In this case no cyst formation takes place. Only the trophozoite form is seen, that is 5-35µm in diameter, (usually 10-20µm in diameter). They produce multiple pseudopodia, which are blunt and large. The chromatin granules lining the inner surface of nuclear membrane are small and continuous. They are transmitted by direct contact from the mouth.

 

E. bovis          

This parasite is found in cattle. The sizes of trophozoites are 5-20µm, cytoplasm filled with vacuoles. Nucleus is large and with a large central endosome made up of a compact mass of granules. The cyst is uninucleated and size is about 4-15µm in diameter.

 

Amoebae with 8 nucleated cyst- E. coli

Amoebae with 4 nucleated cyst - E. histolytica, E. hartmanni, E. equi etc.

Amoebae with 1 nucleated cyst - E. bovis, E. ovis, E. suis etc.

Amoebae with unknown nucleated cyst -  E. canibuccalis etc.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Family-Trypanosomatidae

 

These are leaf like or rounded organisms. Only two genera are important for veterinary.

1 Trypanosoma

2 Leishmania

 

General characters of the family Trypanosomatidae

These are commonly known as Trypanosome and they are found in blood and tissue fluid but rarely on the tissue of the mammals and birds. During their life cycle most of the parasites show at least one further developmental stage undergone in the insect vector that are morphologically different from each other. These stages are,

1-Amastigote        -Previously Leishmanial form

2-Promastigote     - Previously Leptomonad form

3 Epimastigote     - Previously Crithidia form or barley corn form

4 Trypomastigote - Previously Trypanosome form

5 Opisthomastigot -Previously Trypanosome or trypanomorphic form or Herpetomonad form

6 Choanomastigote -Previously Barley corn form

 

 

 

 

The different characters of these stages are:

S.No.	Characters	Amastigote	Promastigote	Epimastigote	Trypomastigote
1	Shape	circular or oval	leaf like or elongate	leaf like or elongate	leaf like or elongate
2	Nucleus position	central or periphery	at the middle of the body	at the post end of the body	at the middle of the body
3	Kinetoplast	rod shaped or present in front of the nucleus	dot like and present ant. to the nucleus at the ant. tip of the body.	dot like but present at the middle of the body ant to the nucleus	dot like present post. to the nucleus.
5	Flagellum and undulating membrane	Absent	flagellum present but undulating membrane absent	flagellum and small undulating membrane present	flagellum and undulating membrane well developed
6	Host	vertebrates	invertebrate such as arthropods	arthropods	Vertebrates
7	Development	develop into promastigote form inside the insect vector	develop into amastigote form inside the vertebrate host.	develop into promastigote form inside the arthropods vector	may develop into previous 3 stages.

 

 

       

Genus Trypanosoma

 

These are found in the blood and tissue fluid and a few species are also found inside the tissue of mammals, birds and reptiles. These parasites may be polymorphic or monomorphic.

Polymorphic - The same spp. has got numerous forms such as elongated, epimastic and metacyclic form in insect host.

Monomorphic - It does not change the shape and size throughout their development. These are transmitted by insect vector. Both forms are usually transmitted by insect vector, inside the vector mainly two process occur.

Any Trypanosome can be mechanically transmitted that is, there is no cyclical development in an arthropod.

According to cyclical development, Trypanosoma has two types of development cycle inside the insect vector.

a.       Anterior station development

b.      Posterior station development

 

Classification of genus Trypanosoma - According to the developmental cycle inside the insect vector, the development of Trypanosoma divided into two sections-

a.       Anterior Station Development or Salivaria

b.      Posterior Station Development or Stercoraria

 

 

a.       Anterior Station Development or Salivaria - The kinetoplast is small and more terminal or subterminal, post. extremity blunt, may be no free flagellum, undulating  membrane is well developed

1. Brucei group- All are polymorphic, intracellular forms have been found in some speces, parasite is long, intermediate and stumpy form. They are found in the intracellular tissue fluid and cyclical development present in mid gut, proboscis and salivary gland of Glossina spp.

   i T. brucei- Parasite developed on the posterior part of the mid gut of G. morsitans, parasite of  sheep, goat, other domesticated animals and in antelops. The parasite causes "Nagana" disease in domesticated animals in West Coast of Africa.

    ii.    T. gambiense- Parasite shows polymorphic, found in man and also in antelopes, parasite causes african sleeping sickness in human in West Coast of Africa.

    iii.    T. rhodesiense- Parasite causes Rhodesian trypanosomiasis or East African sleeping sickness of human. The organism is polymorphic.

 

2.   Congolense group- Development of parasite in mid gut and proboscis of G. palpalis, free flagellum is absent. Parasites are intracellular forms, they are monomorphic or polymorphic.

      i  T. congolense - Found in cattle, sheep, horse and pig =Monomorphic

      ii  T. dimorphon  -  "           "    "          "            "        "     "   =     "

      iii  T. simiae       -  Most pathogenic in pig and camel, horse and cattle are also infected, they are  polymorphic. 

3.   Vivax group- Monomorphic development occurs only in the proboscis of tsetse fly and free flagellum present and high sugar utilized.

      I  T. vivax           -  cattle, sheep, goat and antelope.

      ii  T. uniformae-     "            "         "       "       ". Non pathogenic for goats.

4. Evansi group - Although it belongs to salivaria no cyclical development takes place inside the insect host and they are transmitted mechanically. All species show polymorphism.

i.   T. evansi      - Only found in the proboscis of Stomoxys, Tabanus etc., and survive only 10-15 minutes. They cause a disease condition called "Surra" and infected to cattle, horse, mule, dog, camel and elephant.

ii.   T. equinum   - They cause Mal de caderas disease or weakness of the hinder quarters result in a staggering gait in horse.

iii.   T. equiperdum -Causes venereal diseases (Stallion's disease or Dourine) in horse or mule.

2. Section stercoraria (posterior station development) -Parasite consists large kinetoplast and which is not in terminal position, the posterior extremity is tapering, free flagellum present, undulating membrane not well developed. This section consist only one group.

Lewisi group

i .    T. lewisi - Rat acts as the host, transmitted by rat flea Ceratophyllus fasciatus.

ii.    T. theileri - Cattle acts as the host, in ordinary condition it is non-pathogenic.

iii.   T. melophagium - Transmitted by sheep ked in sheep not so pathogenic.

iv.    T. rangeli -  Dog acts as host.

v.      T. gallinarum - Hosts are fowl and other birds found in South East Asia.

vi.    T. avium        -   "        "       "       "       "        "          "      " Europe, Canada, and N. America. All are nonpathogenicexcept T. cruzi.

vii.    T. cruzi   - Cause "Chagas" disease in man and dog in South America.

Out of these groups only the evansi group are the pathogenic, which found in Indian subcontinent, in North Africa, in Philippine and Central and South America. Other species transmitted by Glossina spp., which is not found in Nepal and India.

Most of the species are naturally transmitted by the cyclical development inside the insect vector and transmitted. A few spp. of Trypanosome can be transmitted machanically (in exceptional condition they are transmitted mechanically).

 

Developmental stages

Inside the definitive host- After the metacyclic form of parasites are injected into the blood of host by infected arthropods vector, they change into trypomastigote form in blood and multiplication occur by longitudinal binary fission. No sexual process has been observed. Division commences at the kinetoplast followed by the nucleus and then cytoplasm. The flagellum do not divide and remains attached to one individual and second daughter individual develops new flagellum. Later trypomatigote form changed into intermediate form and short stumpy form, which is carried by the insect host.

 

Development inside the insect vector. The evansi spp. of Trypanosome does not undergo any cyclical development inside the insect vector and they are transmitted mechanically. For this mechanical transmission the feeding habit of the vector plays role the parasite being mechanically transmitted immediately if the flies bite                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                         another host immediately after sucking blood from the infected host. In the cyclical development, the development may be anterior station or posterior station.  In the anterior station, development occurs inside the mid gut, proventriculus, salivary gland and proboscis of insect. In the posterior station, development occurs in the hindgut of the insect.

 

Anterior Station Development- Three groups of Trypanosome develops in the anterior station of the flies.  Out of these the Brucei group develop in the, 1.  midgut, 2. proventriculus, 3. Salivary gland. The Congolense group develops in midgut and proboscis and Vivax group develop only in the proboscis. In this case (A. S. D.) Glossina flies acts as intermediate host. In the polymorphic trypanosome, the stumpy form of Trypanosomes are responsible for initiating development in the insect vector and they change into elongated form of trypomastigote form, epimastigote form inside the insect vector and then in the proboscis of insect vector they develop into metacyclic form or trypomastigote form. It is the infective form and it resembles to stumpy form of tryponastigote found in definite host.e.g.  T. brucei, T. congolense and T. vivax developed in Glossina fly.

Posteriror Station Development- Only one group i.e., Lewisi developed in this manner. Intermediate or insect vector may be different for different species such as fleas, bugs -bed bug (Reduviid bug) and Triatoma spp. of bug (kissing bug), Triatoma spp. acts as vector of T. cruzi, Melophagus ovinus (sheep ked). In this case development occur in hindgut and they develop into epimastigote form and then into metacyclic trypanosome. These metacyclic trypanosomes are padded out in the faeces, infection occurs after contaminated the skin wounds by the faeces.

e.g. of T. cruzi, T. lewisi etc. developed in the body of kissing bug and flea.

 

Pathogenesis and symptoms-

1. The bites of fly or insect cause small papillae formation on the skin with skin irritation.
2. The multiplication of Trypanosome in the blood of host produces the following symptoms-

1. Pyrexia (rise of temperature)
2. Progressive anaemia
3. Paleness of visible mucous membrane e.g. lip and conjunctiva
4. Oedema of the dependent parts of the body
5. There is emaciation and animal is unable to rise.
6. There is diffculty in respiration leading to death.

Blood alteration

1. The Hb and RBC value are reduced up to 25% of the normal value.
2. There is decrease in potassium contain of the blood and increase in sodium.
3. There is decrease in the leukocytic count, which may cause death.
4. The pH of the blood decreases and it becomes up to 5.5.
5. There is decrease in albumin contains of blood and increase in euglobulin contains.

Changes in the nervous system

In some cases the Trypanosome penetrates through the blood capillary and reaches the cerebro-spinal fluid and cause 1. Encephalomeningitis. In the brain parenchyma they cause 2. Hyaline vacuolated cells known as mononuclear cells of central nervous system.

Causes of death in case of trypanosomiasis-

The actual cause of death is not known but death may be due to following reasons.

1. Hypoglycaemia-The Trypanosome consumes lot of blood sugar due to which there is hypoglycaemia (less sugar).
2. Asphyxia or hypoxia-This is due to decrease in blood sugar level due to which there is increase in lactic acid  and reduces the ability to carry oxygen by Hb, there is difficult in respiration.
3. Stress factor- Loss of glucose shows stress on the liver resulting in disfunctioning of liver and toxaemia.
4. Endotoxins- Disintegration of Trypanosome may result in the formation of endotoxins, this endotoxin is proteolytic in nature and death may occur due to this endotoxin.

Postmortem changes-

Enlargement of spleen, liver, lymph gland, bone marrow is congested, there is gelatinous infiltration of the subcutaneous tissue, pinpoint haemorrhages of visible mucous membrane and sub cutaneous tissue. There is congestion and haemorrhage in stomach and intestine. In the eye there is keratitis and conjunctivities.

 

Diagnosis

1. Microscopic
2. Biological
3. Cultural
4. Serological
5. Xenodiagnosis

1. Microscopic- Examination of blood, serous fluid and cerebro-spinal fluid, often stained with Giemsa stain and Leishman stain.
2. Biological - 1-5ml of affected blood may be injected into peritoneally or I/V into the susceptible laboratory animal. Such as rat, mice, guinea pigs. Rat and guenea pig shows the symptoms within 2-3 days. Guinea pigs and rabbits take one week to show the symptoms.
3. Cultural- Non pathogenic Trypanosomes can be cultured in NNN medium (Novy and MacNeal Nicolle). All Trypanosomes can be cultured in chick embryo.
4. Serological-

i.                    Formal gel test- When a drop of formalin is added to 1ml of suspected serum. In positive case gel formation takes place.

ii.                  Mercuric Chloride test-It is specific for camel when drop of 1:25000or 1:30000 dilution of mercuric chloride is added to 1 drop of suspected serum while precipitation takes place within few minutes indicating the positive reaction.

iii.                Stilbamide test-It is specific for cattle serum from suspected animal is collected and kept for 48 hrs. in refrigerator when a drop of this serum is added to 1 ml of 0.3% solⁿ of stilbamide in distill water. The following reaction takes place. In strongly positive cases the serum coagulates immediately (after one or two minutes) and sinks to the bottom as a large mass and it again dissolved within 5 minutes. In mild positive test the serum drop sinks to the bottom but it dissolve slowly. In light p0ositive case the serum drop sinks to the bottoms as a fine thread and it dissolves slowly. In negative the serum drop is coagulated on the surface and dissolves quickly.

4        Xenodiagnosis- The insect vector is allowed to bite the suspected animal and then these insects are dissected to see the developmental stages of parasites inside the inseect vector.

 

Treatment-

1. Tartar emetic - 1gm (1g. dissolve in 100ml distill water, 20-35ml I/V at 7days interval for 6-8 times at weekly interval. In horse 4g/45kg.b.wt.
2. Naganol/Suramine - 1-2ml /100kg. b.wt. given as 10%solⁿ
3. Naganol and Tartar emetic-4 injections of tartar emetic, then 3 injections of Naganol given at the sequence of NTTNTTN.
4. Antrycide methyl sulfate (Quinapyramine dimethyl sulfate) 5mg/kg b.wt. S/C as 10% solⁿ
5. Antimosan- 3mg/kg b. wt. S/C
6. Berenil-0.8-1.6 mg/kg injection. It is a selective (leading drug) and it useful those which are resistance to other drugs.

Control-

Use of fly repellant and insecticides, control of breeding of insect vectors.

Immunity- The most important immunological aspect is that though antibodies are produced it does not act against the parasites due to production of relapse strain with different antigenic characters. Since the antibodies produced against previous strains can not destroyed due to repeated change of antigenic character.

Species of Trypanosome

Evansi group-

1.T.evansi-Most prevalent species of Trypanosoma in Nepal and India is T. evansi, which is cause "Surra"disease, it is derived from Hindi word sudda.

Host- Horse, camels, cattle, buffaloes and dogs. 

Transmission- This is mechanically transmitted by different spp. of fly belonging to the genera Tabanus, Stomoxys, Haematobia and Lyperosia etc

Symptoms in horses

a. Surra is always fatal in case of horse and death occurs between three weeks to three months of infection.

b. There is high rise of temperature about 104-106⁰F

c. There is watery nasal discharge seen.

d. There is oedema of the limbs, chest region and sheath of the scrotum.

e. Gradual emaciation and weakness develops.

f. There is conjenctivities, paralysis of hind ligs followed by death.

Symptoms in cattle and buffalo- Here four form of the disease are seen.

a.       Slow developing form.

b.      Acute and rapid developing form.

c.       Hyper acute type.

d.      Latent type of these four types the rapid and acute form is more common and symptoms is -

The animals are excite with high rise of temperature from 103⁰-105⁰F

Nervous symptoms- Such as circulatory and striking the head to hard object. These symptom of nervous excitement last for 2-6 hrs. Thus the animal becomes depressed and lies down. Such period of excitement and depression last for 3days during which period the animal may die or recover sometime the animal may die without showing symptoms.

The affected animal looks dull and sleepiness.

            Dogs -

a.       There is rise of temperature

b.      The conjunctiva is congested.

c.       Oedema of head, throats and limbs.

d.      Corneal opacity, keratitis, these may be partial or completely blindness.

e.       The pulse and respiration rate increased and death occurs with in 1-3 month's time.

2. T.equinum- Morphological different is in this case kinetoplast is absent. It causes the disease condition called "Mal de caderas" in equine. The symptoms are

a.       Rise of temperature. b. Weakness of the hind legs. c. Paralysis of the hind leg followed by death. Tabanus fly mechanically transmits these parasites. Mostly occurs in S. America, Argentina, Bolivia and Paraguay.

3. T.equiperdum- It is commonly known as tissue trypanosome because it is found in the genital tissue of equine and disease produced by this species is known as "Mal de coitus" or "Dourine" or "Horse sleepless". It is transmitted mechanically by coitus. Mostly found in North and South Africa, Central and South America, The Middle East and Asiatic Russia.

Lewisi group- It is not prevalence in Indian subcontinent region.

1.      T. lewisi- Occurs in rat and transmitted by rat flea, it is non- pathogenic.

2.      T. theileri - This parasite is transmitted by Tabanus and Haematopota fly. It is the largest Trypanosome and non -pathogenic.

3.      T. cruzi- It causes "Chaga's"disease in human being mostly in children of Southy America and transmitted by kissing bug (Triatoma magista)

4.      T. melophagium- In sheep this parasite is transmitted by Melophagus ovinus (sheep ked) and it is non-pathogenic.

5.      T. rangeli- This parasite is found in blood of man, dog, cat, opossum and monkey and transmitted by Triatomid bugs, development occurs in fore gut and hind gut and not so pathogenic. Rudiviid bug Rhodnius prolixus is the main vector.

Brucei group

1.      T. brucei- Prevalent in South Africa and causes a disease condition called "Nagana" in cattle, horse and dog and transmitted by Glossina fly.

2.      T. gambiense- It is also prevalent in South Africa causes a disease condition called sleeping sickness in man, sometime pigs, cattle and dog are also infected. This parasite is transmitted by Glossina palpalis. Mostly prevalence in West Coast of Africa.

3.      T. rodesiense- This parasite causes rhodensiense disease or East African sleeping sickness in man and trasmitted by Glossina morsitans.

Vivax group

1.      T. vivax - The disease produced by this is also known as "Nagana". This parasite produces chronic and acute type of Nagana in case of sheep, goat, cattle and it is chronic in Africa and mainly transmitted by Glossina morsitans.

2.      T. uniformae-  It also produces the disease called Nagana in sheep and cattle.

Congolense group

1.      T.congolense- This parasite produces acute and serious types of "Nagana" disease in sheep, goat, cattle, horse and pig and it is found in the plasma of these animals. It is transmitted by different species of Glossina spp.

2.      T. dimorphon- Size of the of the parasite is about 11-24um length and is dimorphic, slender, has no free flagellum and the kinetoplast is marginals and subterminal. It occurs in domesticated and wildly distributed in Africa and transmitted by Glossina spp.

3.      T. simiae (syn.T. porci, T. ignotum, T. rodhaini)- This is polymorphic form resembling T. congolense. The majority of the parasites are 16-24um in length, being long and stout with a distinct undulating membrane. It is highly pathogenic for pigs and camels. It is mostly distributed in tropical East and Central Africa and transmitted by different spp. of Glossina.

 

Zoonotic Importance of Trypanosoma- The species, which is found in Nepal and India is evansi group are not zoonotic importance. Though some accidental infection has takes place in man they are not of importance. Natural transmission is not seen in animal to man. But African types of Trypanosoma the species that infect the man such as T. gambiense and T. rhodensiense are also found in domesticated animals and wild animals. These animals act as reservoir host for human infection.  

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Genus Leishmania

 

Leishmania is primarily a disease of man and dog, jackal, rodents' etc act as reservoir host. The Leishmania strains, which are found in Nepal and India, are mainly L. donovani do not use as reservoir host. These are intracellular parasite of macrophases and reticulo-endothelial cell of spleen, liver, bone marrow, lymphnodes, skin and bone marrow.

Morphology- The parasite exists two forms:

1.      Amastigote form: Occurs in vertebrate host.

2.      Promastigote form: Occurs in (I) gut of sand fly and (II) artificial culture.

 Amastigote form (A flageller stage): The parasite at this stage resides in the cells of the reticulo-endothelial system of vertebrate hosts (man, dog and rodents).

The characters of the amastigote form are as follows:

It is rounded or oval body measuring 2 to 4 um along the longitudinal axis. Cell membrane is delicate and can be demonstrated in fresh specimens only. Nucleus measures a little less than 1um in diameter. It is oval or rounded and is usually situated in the middle of the cells or along the side of cell membrane. Kinetoplast lies tangentially or at right angle to the nucleus. It comprises a DNA containing body and a mitochondria structure. Axonemes (rhizoplast) are a delicate filament extending from the kinetoplast to the margin of the body. It represents the root of the flagellum. Vacuole, a clear unstained space lying alongside the axoneme.

Promastigote form (Flagellete stage): This stage of the parasite is only encountered in cultures and in insect vectors.

The earliar ones are short oval, or pear-shaped bodies, measuring 5 to 10 µm in length by 2 to 3 µm in breadth. The fully developed ones are long slender, spindle shaped bodies, measuring 15 to 20 µm in length by 1 to 2 µm in breadth. Nucleus is situated centrally. Kinetoplast lies transversely near the anterior end. Vacuole is a light staining area lying in front of the kinetoplast over which the root of the flagellum runs. Flagellum may be of the same length as the body or even longer, projecting from the front. The flagellum does not curve round the body of the parasite and therefore there is no undulating membrane.

 

 

 

Life cycle- The Leishmania parasites are ingested by sand flies (Phlebotomus spp.) while sucking blood from infected hosts. These parasites reach the midgut of the sand flies where they change into promastigote form and the promastigote form multiply in the midgut by binary fission. After 6-9 days they move forward and block the pharynx of sand fly. When these flies bite a new host these promastigote form are injected into the blood vessels of skin, Then these promastigote form are engulfed by the macrophages and changes into Leishmania form or amastigote form and by means of blood circulation reach various organ of the body. Infection of animal and man is mainly by biting of infected flies. But some time when the infected flies are crushed over the broken skin infection may also take place. There are three spp. of Leishmania.

L. donovani

L. tropica

L. brasiliensis

Infection- D. N. Banerjee (1955) has reported that congenital transmission also occurs through blood.

Symmers (1960) possible transmission by coitus a curious case of women who had never left England but who developed a leishmanial sore on the vulva, her husband had inadequate treatment of Sudanese kala-azar some years before.

Comparative studies of three species of Leishmania

S.N.	Characters	L. donovani	L. tropica	L. brasiliensis
1	D. H.	man, dog, jackal & rodents	man and dog	man and forest rodents
2	I. H.	P.argentipes, P. major, P. orientalis, Lutzomyia spp.	P.papatasi & P.sergenti	Lutzomyia spp.
3	Location	macrophages & cell of the R.E.S.	macrophages & clasmaptocytes of R.E.of skin,endothelial cell of capillaries & lymph nodes of skin	endothelial & large mononuclear cells of skin &mucous membrane of nose, mouth & pharynx
4	Disease	visceral leishmaniasis Kala-azar,delhi fever, dumdum fever, tropical splenomegally	cutaneous leishmaniasis, delhi boil, allepobutton, oriental sore	muco-cutaneous leishmaniasis, euspondia, Uta
5	Incubation period	3-6month, some time 1-2 yrs.	few week to six month or some time 1-2 yrs.	a few days to few weeks

 

Pathogenicity -

Visceral leishmaniasis caused by L. donovani- Soon after the promastigote form are injected in the skin capillary by the sand flies a local reaction takes place. There is infiltration of large no. of macrophages resulting in the formation of papillae on the skin. These macrophages engulf the promastigote form in which Leishmania stage is formed. They are carried into different organ of the body such as liver, lymph gland, spleen and bone marrow where they grow, multiply and resulting in impairment of their functions. From this it is seen that Leishmania donovani or visceral leishmaniasis may result into cutaneous leishmaniasis but not vice versa. The incubation period is about 3-6 months but it may exceed, some time it takes one or two years. The main pathogenicity of Indian kala-azar is splenomegaly, hepatomegaly with fever and weight loss. The haemopoetic process gets hampered leading to anaemia, leucopenia with neutropenia and thrombocytopenia. There may occur hypoproteinaemia, reduced immunity and muscle wasting.

Clinical symptoms-The initial pathogenesis and symptoms are fever, headache,   progressive enlargement of spleen and lymph gland caused lymphadenopathy, occasionally acute abdominal pain and profound anaemia with haemoglobin level 5-10mg/100ml. Later on the symptoms are, there is marked enlargement of spleen and liver, anaemia, emaciation, oedema of skin, diarrhoea, bleeding from the mucous membrane of gum region or epistaxis may be a presenting symptoms. If untreated 74-95% of patients die within a period of 2yrs.

Post Kala-azar Dermal Leishmaniasis (PKDL)- Post Kala-azar Dermal Leishmaniasis (PKDL) is a morbid condition of kala-azar. This is a type of non-ulcerative cutaneous lesion prevalent in endemic areas of kala-azar in India, Bangladesh and some part of Africa. Reports of PKDL in China and Iraq have also been documented. It develops in about 10% of kala-azar patients generally one or two years after completion of antimonial treatment. This phenomenon is the result of an immune response on the part of the host that protects viscera but not the skin, PKDL vary considerably in appearance and these lesions are three forms.

1.Depigmented macular- These are the earlier lesions. These lesions are mostly occur in the trunk and extremities but face is less commonly affected.

2.Erythematous patches- Theses are also earlier lesions which appear on the nose, cheeks and chin. They are very photo-sensitive, becoming prominent towards the middle of the day.

3.Yellowish pink nodules- these replace the earlier lesions and usually not appear from the very beginning. The lesions are mostly found on the skin and rarely on the mucous membrane of the tongue and eye. Lesions are mostly found on the face region.

 

 

2.Cutaneous leishmaniasis-The promastigote form multiply in the macrophages and change into leishmanial form. They again multiply inside the macrophages resulting in the rupture of macrophages and new macrophages are infected there                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                 in the ulceration area. The ulcer persists for several months.

Moist- In the moist form it takes an acute course and very few parasites are found in the ulcerated area. These ulcers are formed rapidly and heal up spontaneously. There is loss of hair in ulcerated area.

Muco-cutaneous leishmaniasis or euspondia -This leishmaniasis is due to L. brasiliensis. It not seen in Nepal and India but it cause severe and horrible skin lesions are found in the mucous membrane of mouth, nose and pharynx. They take considerably long time to heal up.

Diagnosis-

1-Microscopical examination- For this purpose different material is examined.

a.       Skin scrapping or smear prepared from the skin scrapping which is taken from the periphery of the ulcer.

b.      Blood smear examination- After staining the leishman or Giemsa stain.

c.       Smear from biopsy material such as from the spleen, lymphnode, liver, iliac-creast or sternum and bone marrow and finding the Leishmania parasite.

d.      After post-mortem- Impress as smear prepared from spleen, liver and bone marrow may be examined.

2         Cultural method- Leishmania parasite can be cultured in NNN media. For this suspected blood, biopsy material, post-mortem or skin scrapping only for L. brasiliensis may put in the culture in NNN (Novy- MacNeal-Nickolle) media and promastigote forms are found in the positive cases, it takes one month.

3         Biolobical method- The blood or skin scrapping on infected animal are injected intraperitoneally to rat or this may be injected subcutaneously at the base of the tail and in +ve case skin lesion or visceral lesion are found.

4         Serological test- Formal gel test or Henery's gel test- If a drop of formalin is added to a drop of suspected serum in +ve cases gel formation takes place and whole mixture becomes milky white in colour, It is more reliable in dog infection.

5         Chopra's et. al, antimony test- About 3-4 ml suspected serum is taken in test-tube and 1-2 ml of 4% urea stibamine is gradually added in +ve case precipitate are formed at the bottom of the test-tube.

Treatment-

1 Mapacrine-dose 10% solⁿ of mepacrine1-2ml injected at the site of the skin lesions.

2 Fuadin- dose 0.1-0.2gm in 2ml of distill water and injected  I/m.

3 Pentamidine- dose 2mg/kg b.wt dissolved in 2-5ml of distilled water injected I/m.

 has satifactory result.

5        Sodium Antimony Gluconate- 6-8gm I/V available in 20,40or 100mg/ml of concentration.

6        Amphotericin B (Fungizone) an antifungal agent

.1mg/kg of b.wt. daily by slow I/V dissolve in .5litre of 5% dextrose (given over 6hrs.). It may be increased to 0.25mg/kg b. wt. total dose should not be more than 2gm.

Control

By controlling the sand fly or Phlebotomus flies.Once the man infected by this disease and active acquired immunity develop inside the cured human being. The man is resistant for that disease throughout the life.

 

Order-Diplomonadida

 

Family-Hexamitidae

 

Giardia lamblia

Synonym- Giardia intestinalis or Lamblia intestinalis

 

Location and host: The organism is found in the duodenum and other parts of the small intestine and occasionally in the colon of man, monkeys, pigs and rats.

Morphology: It exists in two phases i.e., trophozoite and cysts.

Trophozoite- Size of trophozoite is 14µm long by 7µm broad. The body of the parasite is pear shaped. Anterior end is broadly rounded and posterior is pointed. The dorsal surface is convex and ventral surface is concave. The body is bilaterally symmetrical. The anterior half of body has large disk like structure known as sucking disk and this sucking disk contain two nuclei both are vesicular type. Pair of dark staining body known as parabasal body are present in center. There are two axostyles and two nuclei and four pairs of flagella. Multiplication of vegetative form is longitudinal binary fission.

 

Cyst- The fully formed cyst is oval in shape and measures 12 um long by 7 um broad. The axostyles lie more or less diagonally, forming a sort of dividing line within the cyst-wall. There are four nuclei, which may remain in cluster at one end or lie in pairs at opposite poles. The remains of the flagella and the margins of the sucking disc may be seen inside the cytoplasm.

Transmission - It is mainly by contaminated food and water.

Pathogenesis and symptoms- These are more pathogenic in human being and mostly children suffer more than other animals.

Symptoms- Chronic diarrhea containing more mucous. This also hampers in the fat metabolism by forming a layer over the intestinal mucosa- defective fat metabolism called steatorrhoea, resulting in the deficiency of fat soluble vitamins.

Diagnosis- By finding the cyst in the faces.

Treatment- Similar to amoebiasis.

Mepacrine (atebrin) – 200 mg daily for 30 days.

Meteronidazole (flagyl)- 100 mg thrice a day for 3-5 days.

Chloroquine – 300 mg daily for 5 days in human and pig.

Emetine hydrogen chloride -0.5-1 gm I/M or S/C injection for 10 days.

Other spp. of Giardia that are found in the domestic animals are G. canis, G. cati, G. bovis, G. caprae, G. equi, G. muris (mouse or rat), G. duodenalis (rabbit), G. cavie (guinea pig) etc.

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

 

Hexamita meleagridis

Location and host- This parasite is found principally in the duodenum and small intestine of young turkeys. It is also found in the bursa of Fabricious and caeca of domesticated adult birds and wild birds like peafowl and various pheasants etc. It is found throughout the world and is quite common.

Morphology- Organism is bilaterally symmetrical, pear shaped and measures 6-12 µm in length by 2-5µm broad. The six anteriorly directed and two posterior directed flagella are present. There are two nuclei and two axostyles.

 

Life cycle- Trophozoite of parasite multiplies by longitudinal binary fission. There are no cysts, and transmission is direct from bird to bird through contaminated feed and drinking water.

Pathogenesis and symptoms- Young turkey up to the age of about two months are the most susceptible. Death may occur within a week of infection in some cases, and the mortality in the flock may reach up to 80%. There is catarrhal enteritis of the upper digestive tract and this produces a marked lack of tone in the duodenum and jejunum. The small intestine is inflammed and oedematous, there is congestion of the glandular tissue of the caecum. The diseased birds also produced watery diarrhoea, later it becomes listless, loss weight rapidly and finally dies. If birds are recovered they grow poorly and may act as carriers.

Diagnosis- This is made by the demonstration of living organisms in a drop of the contents of the small intestine.

Treatment-

Furazolidone: at a rate of 110mg/kg live weight, mixed in feed could be prevented by continous feeding.

Nithiazide: at a concentration of 0.02% in drinking water controlls fatal out breaks due to Hexamita and Histomonas in turkey.

 

 

 

 

 

Order- Trichomonadida

 

Family-Monocerco monadidae

 

Histomonas meleagridis

 

Geographical distribution- It is world wide in distribution

Location and host- Found in the caecum and liver of turkey and also sometime in fowls. It is mostly a disease in young poults between 2-12 weeks of age. It causes histomoniasis, infectious enterohepatitis or 'black-head,' in the turkey. It may also occur in the chicken, peafowl, guinea fowl, pheasant, partridge and quail.

Morphology- it is extracellular parasite and pleomorphic in characters. It is amoeboid and contains one or more pseudopodia. It measure 5-30 µm in diameter. It has clear ectoplasm and granular endoplasm. Endoplasm contains food vacuoles with bacteria and starch granules. Nucleus is vesicular and only one flagellum or in some there are two flagella and axostyle also present. No cyst formation takes place. It multiplies by binary fission.

Transmission- By engestion of trophozoites which are passed out in faeces. By infection of embryonated egg of Heterakis gallinarum, which carries the parasite from caecum of birds. Incubation period is 15-20 days.

Pathogenesis - Parasite penetrates the caecal wall and causes the necrotic ulcer. Lesions are mostly found in caecum and liver. Caeca are filled with lot of exudates, which later on becomes very hard. The liver is greatly enlarged and contains circular ulcer with a depression in the centre. The ulcers are first yellowish green and later on a fibrous tissue capsule of white colour surrounds them. Necrotic foci may sometimes be seen in the kidney.

Symptoms- Young birds are more susceptible and adults act as carrier. Depression, dropping wings, lower head and sulfur yellow colour diarrhoea. The disease lasts for 3-10 days. Because of the cardiac weakness the feather less part of the head has a cyanotic blue colour or black.

Diagnosis- From the symptoms i.e, sulfurs yellow colour diarrhoea.

Postmortem characteristic- liver ulcer.

Finding the trophozoites in faeces.

Treatment-  i. Furazolidone - 0.01-0.02% concentration in food in a day.

ii. Entramin - 0.05% as prophylactic and 0.1-0.2% as curative

iii. Nitrofurazone- given in food 0.1-0.4%

iv.                NAB (Nav arseno billon) 0.1c.c./lb. b. wt. 5% solⁿ intransmuscularly, may be repeated once after 3 days.

v.                  Nithiazide at a concentration of 0.02% in drinking water.

 

Control- Good management and hygiene.

Turkeys and chickens should be raised separately.

Young birds should be kept separately.

Treatment of caecal worm i.e, H. gallinarum by phenothiazine. Levamisole, piperazine.

 

Parahistomonas wenrichi

 

The parasite is similar to Histomonas but it consist four flagella instead of one or two, an axostyle and there is rod -shaped parabasal body. This species is not pathogenic for gallinaceous birds. Chiefly found in caeca of pheasant and turkey. It measure 9-27 µm in diameter. It does not multiply in the host tussues, nor does it show any visible pathological signs. The embryonated eggs of Hererakis gallinarum transmit it

Monocercomonas ruminantium

This parasite is found in the rumen of cattle and it is non-pathogenic. It has only one flagellum.

 

 

 

 

 

Family - Trichomonadidae.

 

Trichomonas

 

Parasite consists 4-6 flagella, out of these only one flagellum runs backward as trailing flagellum.

There are two families-

Trichomonadidae

Monocercomonadidae

Trichomonadidae- Only one genus is important.

Genus- Trichomonas and Tritrichomonas. It has got number of species.

Tritrichomonas foetus- Found in genital tract of cattle.

T. ruminantium- Found in the rumen of cattle and it is pathogenic.

T. suis- Large trichomonas mostly found in stomach but some time nasal passage, caecum and small intestine. It is non-pathogenic.

T. equi- Found in caecum and colon of horses.

Trichomonas gallinae- Found in upper digestive tract of specially in pigeon and sometimes found in fowls and turkey.

Tetratrichomonas gallinarum- Found in lower digestive tract and sometime in the liver of fowl, turkey and guinea fowl.

 

Tritrichomanas foetus

 

Location and host: These are found in the vagina and uterus of cow and preputial sheath of the bull. In case of heifer they are not found. The disease produced by this is called bovine trichomoniasis or early abortion within 8-16 weeks of gestation. It may also occur in pig, horse and deer but pathogenic effects are seen only in the bovine.

Morphology- These are pear shaped with broad anterior and narrow posterior end. Size of the parasites is 10-25µm by 3-15µm wide. The nucleus is situated at the anterior part of the body. The parabasal body is present, which is sausage shaped or rod like in nature. Supporting structure such as costa and axostyle are present. These are four flagella, out of these three are anterior and 4^th flagellum runs backwords along the body of the parasite being attached to the body with the well developed undulting bembrane and end as free posterior flagellum. At the anterior part of body a cytostome is present. Multiplication takes by longitudinal binary fission. There is no cyst formation.

Transmission: Some parasites are also transmitted by coitus or copulation. A part from these contaminated A.I. instrument or artificial insemination or by gynaecological examination of cows, which acts as source of infection and flies mechanically transmitted the parasite.

Pathogenesis and symptoms: In case of cows the parasite first invades the vagina and cause the initial lesion as vaginitis of varying intensity. The floor of vagina may fill with mucopurulent discharges, these parasites further pass into the uterus through cervix and cause endometritis and pyometra (inflammation of uterus with pus formation). The infected cow may conceive but the parasites do not allow the foetus to grow inside the uterus this results is early abortion. Characteristic of trichyomoniasis is the abortion occurs within 8-16 weeks of gestation.

Two types of abortion is seen-

1. In the first type of pathogenesis both the foetus and foetal membrane are expelled out and not much damage is caused to the wall of the uterus.
2. In second type of pathogenesis only the foetus comes out but the foetal membrane is retained in the uterus and which gradually putrify resulting in pyometra. In such case the cows usually become sterile. In some other cases the death of the foetus inside the uterus, which becomes macerated and catarrh type of endometritis develop. In some other cases within the closed cervix, the serous fluid accumulates inside the uterus resulting in pendulous uterus and in such cases the fluid that is present thus appears grayish white or colourless and contains large number of parasites.

In case of bull: There is inflammation and swelling of preputial sheath and due to this there is pain during micturition and copulation. Small reddish papillae may be present over the prepuce and epididymis and mucopurulent discharge may be present.

Diagnosis:

i. History of the herd- if there is early abortion can suspect this disease.

ii. By microscopical examination of vaginal and uterine discharge: amniotic and allantoic fluid of freshly aborted foetus, and microscopical examination of the washing of the prepuce of the bull. In positive case parasite are found.

iii. Serological type: a. Here one antigen known as tricin is available and thus, 0.1ml of 1:40,000 dilution of tricin is injected intradermally to suspected animal. In positive case a marked swelling is seen within ten minutes of injection. It disappears within 6 hours. It is called intradermal test.

b.      By mucous agglutination test.

 iv. Cultural method- These parasites can be cultured in peptone broth media to which 10% cattle serum and antibiotic like penicillin or streptomycin is added. The culture is kept at 37 c and in positive cases the parasite will grow within 28 hours.

Treatment:

For bulls- Wash the penis with a weak solⁿ of detergent, dried and flavine ointment introduced into the preputial cavity and massaged for 15- 20 minutes. Then wash by means of 1% acriflavine solⁿ to kill the parasite.

For cow- Wash the vagina and uterus with 1% acriflavine or 3% lactic acid solⁿ. Next is berenil 1% soln 100-150c.c. is put into the uterus and kept for 15-30 minutes to kill parasites.

Control: Treatment of infected bulls, castration of infected bulls. Artificial insemination equipment should be properly sterilized. The major control measure for trichomoniasis in cattle is the used of A.I. In infected cow should be given breeding rest. Suspected cows should be kept separate from other animals and without breeding.

 

 

 

 

Phylum- Apicomplexa

 

 

 

Classification

Phylum-Apicomplexa

Class-    Sporozoa

Order-    Coccidia

Family-   Eimeriidae

 

 

General Characters of the class sporozoa- Pseudopodia, flagella and cilia are absent. There is limited motility, which is sufficient to penetrate the cell. It produces spore and sporozoites.

Characters of the family Eimeriidae- These are intracellular parasites, found in epithelial cell of intestine and mostly host specific.

This family has many genera, which are –

Eimeria, Isospora, Wenyonella, Tyzzeria etc.

Eimeria- Sporulated oocyst has four sporocysts and each sporocyst has two sporozoites.

Isospora- Sporulated oocyst has two sporocysts and each sporocyst has four sporozoites.

Wenyonella- Sporulated oocyst has four sporocyst and each sporocyst has four sporozoites.

Tyzzeria- Sporulated oocyst has no sporocyst and oocyst consists eight sporozoites.

 

 

Genus – Eimeria

 

Location- They are intracellular parasites and mostly found in the epithelial cell of intestine but some may also found in liver and kidney of mammals and birds.

Examples are-

E. tenella, E. necatrix, E. acervulina, E. maxima, E. brunetti, E. hagani, E. mitis, E. praecox are found in the alimentary canal of poultry, E. ninakhalakimoviae, E. arlongi, E. faurei, E. intricata etc. are found in the alimentary canal of goat and sheep.

E. stiedai is found in the liver of rabbit and E. truncata is found in the kidney of goose

 

Host- All type of animals and birds act as the host of different species of coccidia. Birds and rabbit are most susceptible host, sheep, goat, cattle, buffalo, pig, dog and cat are less susceptible hosts. Horse and mule are rarely infected. The young animals and chicken are most susceptible and heavily infected.

 

Morphology of unsporulated oocyst- The oocyst which has passed out freshly in faeces is known as unsporulated oocyst. The shape is spherical, oval or cylindrical. It is surrounded by double layer oocyst wall. It is the resistance stage of the life cycle of coccidia. There is a single mass in the centre of the unsporulated oocyst, which is called sporont and under favorable condition it change into sporulated or infective oocyst.

 

Morphology of sporulated oocyst- The development of oocyst outside the host body is known as sporulation. Fully developed oocyst is known as sporulated oocyst and it is infective forms of parasite. Sporulated oocyst of genus Eimeria has four sporocysts and each sporocyst contain two sporozoites. The anterior end has small opening called micropyle. Micropyle is covered by a cap, which is called polar cap. In some species micropyle and polar cap is absent. Below the micropyle there is a clear refractile granule called polar granule. During the formation of sporocyst a portion of cytoplasm is left called oocystic residual body. The narrow end of oocyst is called stieta body. During the formation of sporozoites some cytoplasmic mass is left which is known as sporocystic residual body. The sporozoites are banana shaped. One end is broad and another end is narrowly pointed with a nucleus at the middle. Cytoplasm is granular with a vacuole at each end.

Life cycle- The oocyst are passed in the faeces of host. The freshly passed ooocyst contains a single cell the sporont. They must have oxygen, mosture and suitable temperature in order to develop to the infective stage, a process is known as sporulation or sporogony. The sporont, which is diploid, undergoes mitotic division. The sporont divides directly into four, forming four sporoblasts, each of which then developed into sporocyst. Within these sporocysts, two sporozoites develop. Sporulation usually takes two to four days at ordinary temperature then ready to infect the new host. Definitive host gets the infection through contaminated food and water. In the lumen of the intestine of definitive host the oocyst wall rupture in the gizzard and the sporocysts are ruptured in the small intestine in the presence of carbon dioxide, reaction of enzyme and bile juice. Sporozoites are liberated in small intestine. Sporozoites enter in the epithelial cell of the intestine either directly or via white blood cells and round up to become trophozoites. The nucleus of trophozoites divided mitotically into large number of small bits. This multinucleated body is called schizont. Later a portion of cytoplasm surrounds each bit of nucleus and large numbers of merozoites are formed. When the wall of the schizont is ruptured a large number of uninucleated first generation of merozoites are released. The merozoites of the first generation further attack to the fresh epithelial cells and second generation of merozoites are formed within five days after inoculation (DAI). Some of them enter in new epithelial cells and round up to form third generation of merozoites. The number of merozoite release from the schizont is different according to their species. In this way after 3-5 schizogonous life cycle, many of the merozoites of second generation penetrate again the fresh epithelial cell and start gametogony cycle. They produce male and female gametocytes. The male gametocyte is called microgametocyte and the female gametocyte is called macrogametocyte. During production of merozoites most of the merozoites change into macrogametocytes and few merozoites are change into microgametocytes. Later macrogamete or female gamet is formed from the macrogametocytes and microgamete or male gamete is formed from the microgametocyes. Microgametes are small and having flagella and many microgametes surround the single macrogamete. In case of E. tenella only one microgamete enter inside the macrogamete through the micropyle, the nuclei of both gametes fuse to form zygote. The cytoplasm of zygote shrinks and become hard to form the outer wall, now the zygote is called oocyst. Inside the oocyst the refractile granule joined together to form the inner wall of the oocyst. Oocyst after ruptured the intestinal epithelial cell reach in the lumen of intestine then passed out with the faeces. The freshly passed oocysts are unsporulated. The sporulation of oocyst is depend of the species and the temperature and moisture of the environment. The prepatent period of Eimeria species varies considerably and may be as short as five days in poultry and up to 3-4 weeks in some ruminant species.

Mode of infection- The disease cause by the coccidia is called coccidiosis. Birds are infected by the ingestion of sporulated oocysts of coccidia through the contamination of food and water.

 

Pathogenicity and symptoms- The clinical symptoms of coccidiosis varies with the number of sporulated oocyst ingested and age of the birds and animals. In birds no symptoms are observed till the 4^th day of infection. There are mainly two types of pathogenicity cause by coccidia in birds.

Caecal coccidiosis-This type of coccidiosis is cause by E. tenella, in this case caeca may be filled with blood tinged contents and caecal wall seems patchy or diffuse haemorrhages. Sometimes in chronic cases there may be cheesy cores in congested caeca. In infected birds no symptoms are seen till the 4^th day of infection. When the mature merozoites are released on the 4^th day of infection they pinch upon the capillary of the caecum and cause blood stained faeces passed out. The extensive bleeding occurs on the 5^th day and 80-90% of infected birds may die on 5^th day.

Symptoms are poor growth, emaciation, poor egg production, loss of appetite, restlessness and drooping wings. On the 6^th day there is sluggish movement. There is a sulphur coloured diarrhea- typical symptoms in birds, jaundice may be seen in advance cases. In less acute case the faeces may be chocolate brown or red mixed blood. Occasionally paralysis is seen. Mortality rate is highest between 4-6^th day of infection. Death occurs due to sever blood loss. If the birds survive the oocysts are passed out on 7^th day and birds are usually recovered.

Postmortem Changes- Caeca may be swollen and enlarged, the wall may be thickened and inflammation occurs. On the 3^rd day of infection pinpoint hemorrhages may be seen in the caeca. On the 4^th day of infection a large number of haemorrhagic spot are seen on caecal wall. On the 5^th day of infection caeca filled with large amount of unclotted blood or partly clotted blood. The caecal content contains the schizonts and merozoites. On 7^th day of infection the caeca is filled with fibrineous and necrotic material and large number of oocyst.

Intestinal coccidiosis – E. necatrix causes chronic intestinal coccidiosis and usually the middle 3^rdof the small intestine is mostly infected. The small intestine is greatly swollen with small white small foci. Haemorrhage on 5^th day and lumen of intestine filled with large amount of clotted or unclotted blood.

In E. acervulina the anterior half of small intestine is infected. It causes chronic diseases with mucous diarrhoea but no blood. Intestine is thickened with white transverse patches and the white spots take linear configuration.

In case of E. brunetti, the large intestine, below the caecal junction and in the  terminal part of the small intestine show haemorrhagic enteritis and some time catarrhal enteritis.

Diagnosis- Coccidiosis can be diagnosed by the symptoms, finding the oocyst in faeces, at postmortem- from characteristic lesions on the caeca and small intestine. Intestinal and caecal scrapping will show the presence of oocyst and other developmental stages.

Identification of oocyst- The oocyst of different species can be identified on the basis of their shape, size, colour, location in the host type and degree of their pathogenic lesions and sporulation time. For sporulation the caecal sample positive for coccidia parasite are kept in 2.3% potassium dichromate solution at 25-30⁰c. Sporulation takes place within 48-72 hours.

E. tenella- This species is very common worldwide in distribution, infecting the caeca of the chicken.

Oocyst- The oocysts are ovoid 14-31um by 9-25um in diameter with a smooth, two layered wall without a micropyle or a residue with a polar granule. Sporocysts are ovoid, without a residum. The sporulation time is 18 hours to 2days.

Life cycle- Prepatent period is six days.

Pathogenesis and symptoms- Caecal coccidiosis is found most frequently in young birds. Chickens are most susceptible at four weeks of age. Chicks 1-2 weeks old are more resistance. Older birds developed immunity as the result of exposure. Coccidiosis due to E. tenella may vary in severity from an inappearent infection to an acute, highly fatal disease, depending on the infective dose of oocyst, the pathogenicity of the coccidian strian, the breed and age of the chickens, their states nutrition and other disease and stress often which they are concomitantly subjected. Caecal coccidiosis is an acute disease characterised by diarrhoea and massive caecal haemorrhages. The first sign appears when the second-generation meronts begin to enlarge and produce leakage of blood into caeca. Blood appears in the droppings 4DAI(Day After Infection). The greatest amount of haemorrhage occurs in 5-6 DAI. E. necatrix- This species is common and worldwide in the chicken. The first and second-generation meronts are in the small intestine and the third generation meronts, gamonts and gametes are in the caeca.

Oocyst- The oocysts are ovoid and 12-29µm by 11-24µm in diameter with a smooth colourless, two layered wall, without a residuum. The sporulation time is 18 hours to 2days.

Treatment-

Amprolium- A combination of amprolium and sulphaquinoxaline at levels of 0.006%of each in the food is more effective against poultry coccidia.

Or

Amprolium powder @30 gm dissolve in 25 litres of water for 5-7 days.

ESB₃ powder- 1gm powder dissolves in 1litre of water and provided for 3-6 days.

Supercox- 1gm/1lit. in water for 3days.

                  Only pure water for two days.

                   1gm/2 lit. of water for 3days. = Total eight days should be treated.

Other coccidiostate

Coxistac, Sacox-120, Meridot, Cocciwin, DOT, maduramycin, Salinomycin, Nicarbazine, Monensin, Lasalosids.

 

Suppliments-Vitamin K containing supplements like Kaysol forte powder @ 5gm for 100 birds, liquid  (Multisol K liquid) @5ml/100birds or 10ml/100birds provided for 3-5 days in water.

Vita blend WM Fort (Vit.A) 5 ml/100 birds provided once daily for 3-5 days, it helps in the regeneration of epithelial tissues.

N/B- It is not advisable to supplement Thiamin during treatment with amprolium.

Preventive and control measures of poultry coccidiosis-

1-Destruction of oocyst- The oocysts can be killed by the following methods.

1. Fumigation of poultry house and litters by 0.044% of solution of ammonia. This will kill the oocyst with 2 hours.
2. By application methylbromide at the rate of 1lbs/1000sq. ft’ of poultry litter.                                                  

 

      2.   Proper sanitation and management should be adopted in poultry house.

3. Young birds should be kept separately from adult one.
4. The poultry litters should be kept dry and stirred frequently or it should be changed frequently when it becomes wet.
5. In case of outbreaks the sick birds should be removed immediately and kept in a separate house. The remaining healthy birds should be treated with coccidiostats for preventing the disease and the infected litter should be changed.
6. As the oocysts can be carried by cloths of attendants of the poultry house the shoes should be removed out side the poultry house before entering into it.
7. In some places vaccines are used against coccidiosis. These vaccines are helpful by immunising the chick. The vaccines are prepared from a mixture of four common pathogenic species such as E. tenella, E. necatrix, E. acervulum and E .maxima, some time also for E. hagani. These oocysts mixture is given to 3-5 days old chick in a small dose mixed with the feed. Along with this oocyst some coccidiostate are also given to check the clinical sign of infection.

 

Coccidiosis in rabbits

The species of Eimeria found in rabbit are-

E. stiedai – Most pathogenic coccidiosis of rabbit found in liver and bile duct.

E .megna

E perforans

E .irresidua

These all are found in the intestine of rabbit.

 

 

 

 

 Eimeria stiedai

 

Geographical distribution- Cosmopolitan in distribution.

 

Location and host-Parasites are occur in the liver and bile duct of rabbit. This is the commonest and most pathogenic coccidium of domestic rabbits.

Morphology-The unsporulated oocyst is ovoid and some time ellipsoidal with a flat micropylar end, smooth and measures about 26-40µm by 16-25µm in diameter.

Life cycle- The meront (Schizont) are in the epithelial cells of the bile ducts. The number of asexual generation is unknown but is apparently indefinite. At least five or six are known and most of them have two types of meront (schizont). One type of meront produces a small number of plump merozoites and other type produces numerous slender ones. The prepatent period is unknown but it may apparently be several weeks.

Pathogenicity and symptoms- In mild infections little or no clinical signs are evident but in heavy infections severe liver involvement, liver is greatly enlarged with many white spots, in heavy infection cause dirrhoea and death may occur. In fatal cases the liver may be increase five to ten times its normal size. Petechial haemorrhages occur in liver and kidneys. Oedema is seen in the peritoneal cavity and the whole body may be oedematous. E. steidai is a scourge of rabbits and is difficult to eradicate from the colonies.

Treatment- Sodium sulphamezathine – 0.2% in water for 6-7 days highly effective.

                  Sulphaquinoxaline – 0.03% in feed for 6-7 days

                   Sulphaguanidine – 0.5% in feed for 6-7 days

The intestinal forms cause loss of appetite, diarrhoea and rough hair coat. Coccidiosis is the major problem in rabbit and it is one of the major causes of death in rabbit.

 

 

Coccidiosis in sheep and goat

Various species of Eimeria are-

E. arlongi

E. nina = Khol yokimovae

E. faurei

E. intricata

 

E. arlongi is the most pathogenic one. The young animals are mostly affected and symptoms include rest lessness, weakness, abdominal pain, lost of appetite, diarrhoea, which may be fowled, faeces mixed with blood and mucous.

 

Coccidiosis in cattle and buffalo-

 

The species of Eimeria found in cattle and buffalo are-

E. zuernii

E. bovis

E. cylindrica

E. subsperica

 

E. zuernii

 

Geographical distribution- World wide in distribution.

 

Location and host- Schizogony stage of parasites are mostly found in the small intestine and gametogogy stage of the parasite is found in the caecum, colon and rectum of the cattle and buffalo. This species of the coccidium is the most common and most pathogenic ones.

Morphology- The unsporulated oocyst are spherical, sub-spherical to ellipsoidal. The sizes of the oocysts are 15-22µm by 13-15µm in diameter. The oocyst wall is thin, transparent and colourless to pale yellow in colour. The micropyle in not located. Sporulation time is 3days at 20⁰ C and 23-24 hours at 30-32.5⁰C.

Life cycle- By the second and third days of ifection, trophozoites are found in the mucosa, some penetrating as far as the muscularis mucosa. By the six-day schizonts are found in the epithelial cells of the upper and lower parts of the small intestine. Schizonts may still bfe present up to the nineteenth day and by this time parasites occur throughout the small intestine and also in the caecum and colon. Mature schizonts measure up to 7-9.8µm in diameter and it produces 24-26 merozoites. There are two generation of schizogony the first occuring in the lower ileum and the second in the colon and caecum. The earliest sexual stage is the macrogamete and it seen 12 days after infection in the epithelial cells of the villi of the lower small intestine and in the caecum, colon and rectum. The microgamonts are seen first on the fifteenth day, being found in the lower colon and rectum. They are much fewer than the macrogamonts. Oocysts may be found in the tissues of the caecum and colon as early as 12 days after infction but oocyst production is highest at 19-20 days after infection.  

Pathogenicity and symptoms- E. zuernii is the major pathogenic coccidium of cattle and buffalo. Haemorrhagic diarrhoea, anaemia, weakness and emaciation characterized by the acute diseases. In severe infections death may occur as early as seven days after the one set of clinical signs. At postmortem the najor lesions occur in the large intestine, although gerneral catarrhal enteritis may present in both the small and large intestine. Smear from the mucosa show very large number of developmental stages of oocysts.

 

Diagnosis- This disease is diagnosed by the finding of oocysts of parasite in the faecal examination.

 

Treatment- Amprolium- 20-30mg/kg b. wt. daily in feed for 4to 5 days.

                   Lincomycin hydrochloride- 1gm/calf given in the drinking water for 21             

                   days.

 

Preventive measures- The prevention of bovine coccidiosis is base on treatment and good sanitation.

 

E. bovis

 

Geographical distribution- World wide in distribution.

 

Location and host- Schizogony stages of the parasite is mostly occurs in the small intestine and the sexual stages in the caecum, colon and terminal part of the ileum of the ox, zebu and water buffalo.

Morphology- Unsporulated oocysts are ovoid, smooth and average size is 27-29µm by 20-21µm in diameter.

Life cycle- There are two asexual generations. The mature first generation of meronts are about 281µm by303µm in diameter. It is the largest schizont among the all species of Eimeria.and containing average of 120,000 merozoites in each. They are easily visible to the naked eye as whitish balls. They lie in the endothelial cells of the lacteals within the villi in the posterior half of the small intestine. The second generation of meronts or schizonts is in the epithelial cells of the villi of the caecum and colon. The average size is 10um by 9um in diameter in tissue sections and contains 30 to 36 merozoites in each. The gamonts occur in the epithelial cells of the intestinal villi, many in the caecum and colon, but may extend into the small intestine in heavy infections. The prepatent period is 15 to 20 days and the patent period is 5 to 26 days.

Pathogenisis and symptoms- E. bovis is probably the most common cause of coccidiosis in cattle.  In severe infections the majority of the crypts of the large intestine and some time the terminal part of small intestine are destroyed and the lumen of intestime filled with blood. The mucosa is necrotic and this damaged may extend to the subucosa. The wall of the intestine is congested and oedematous.

Diagnosis- By finding oocysts in faecal sample and from the symptoms of the disease.

Treatment- Amprolium 10mg/kg b.wt. for one week.

                    Decoquinate 0.5mg/kg b. wt. , atleast 24 days for protection. 

 

E. tenella

 

This species is very common and world wide and found in the caeca of the chicken.

Oocyst- The oocysts are ovoid and measure about 31µm by 9-35µm in diameter with a smooth, two layered wall without a micropyle or a residuum, with a polargranule. The sporocysts are ovoid, without a residuum. The sporulation time is eighteen hours to two days.

Life cycle- The prepatent period is six days.

Pathogenesis and symptoms- Caecal coccidiosis is found most frequently in young birds. Chickens are most susceptile at four week of age. Chicks 1-2 week old are more resistance. Older birds develop immunity as the result of exposure of coccidiosis due to E. tenella may very in severity from an iappearent infection to an acute, highoy fatal disease, depending on the infective dose of oocyst and age of the chickens. Theirs state of nutrition and the other disease againts and stresses often to which they are concomitantly subjected. Caecal coccidiosis is an acute disease characterized by diarrhoea and massive caecal haemorrhages. The first sign appears when the second-generation meronts begin to enlarge and produce leakage of blood into caeca. Blood appear in the droppings 4DAI (Day After Infection).  The greatest amounts of haemorrhages occur in 5DAI.

 

E. necatrix

 

This species of coccidia is common and World wide in distribution in chicken. The first and second generation of meronts is in the small intestine and the third generation meronts, gamonts and gametes are in the caeca.

Oocyst- The oocysts are ovoid, and measure about 12-29µm by 11-24µm in diameter, with a smooth colourless, two layered wall, without micropyle and a residuum, with a polar granule. The sporocysts are ovoid with a stieda body, without a residuum. The sporulation time is eighteen hours to two days.

Life cycle- The spozoites enter the epithelial cells of the small intestine, pass trough the epithelium into the lamina propria or cone of the villi and migrate toward the muscularis mucosa. Most of them are engulfed by macrophages and are transported by them to the epithelial cells of the fundus.

Pathogenesis and symptoms- Next of E. tenella, this species is most pathogenic and important species of chicken coccidia.

E. necatrix is often said to cause a more chronic type of coccidiosis than E. tenella.

The principal regions are in the small intestine then middle third of which is the most seriously affected. Fourth DAI find small white opaque foci here. Severe haemorrhages may appear on the fith or six-day. Death is usually occurs in 5-7 days after exposure. Many of the birds that recover remain unthrifty and emaciated.

 

Family –Sarcocystidae

1. Sub family- Toxoplasmatinae                     2. Sarcocystinae

Genera a. Toxoplasma                                       a. Sarcocystis                        

3. Besnoitia
4. Hammondia

Characters of the sub family Toxoplasmatinae – Oocyst with two sporocysts, each sporocyst with four sporozoites. Parasites are facultatively or obligatory and heteroxenous. Definitive hosts are feline animals. Merogony in both intermediate and final hosts and infection may occur in intermediate and final hosts. Metrocytes are not formed. Schizonts and gametocytes are found in the enteric cells of felid and sporogony is occurs in the out side of the host body.

 

Toxoplasma gondi

 

Location and host – Definitive host is domestic cat and various wild felines species. About 300 species of almost all warm-blooded animals such as mammals and birds act as intermediate host.

Morphology – Oocysts with two sporocysts and each sporocyst consists four sporozoites. The size of oocysts is about 12µm by 10µm in diameter and size of sporulated oocyst is about 13µm by 10µm in diameter. The size of sporocyst is about 8.5µm by 6µm in diameter and the size of sporozoite is 8µm by 2µm in diameter.

Life cycle- Toxoplasma goni has two developmental cycle i.e., and enteroepithelial cycle and and extraintestinal cycle.

Enteroepithelial cycle – The enteroepithelial cycle occurs in cat. Cat may be infected by sporulated oocyst or by eating bradyzoites or tachyzoites containing tissue of the infected intermediate host.

Kittens are infected with cysts containing bradyzoite derived from mice. Bradyzoites enter intestinal epithlial cells and a number of morphological types of multiplicative stages occur. Multiplicative stage is divided into A, B, C, D, and E. Type A is the smallest multiplictive type and it appears 12-18 hours after infection. Division of A type is by endodyogeny and this type change into type B and it occurs 12-34 hours after infection. Type B has centrally located nucleus and it divides by endodyogeny and endopolygeny and it formed C type and it occurs 24-54 hours after infection. Type C is divided by schizogony and form type D and it occurs from 32 hours to 15 days after infection. Type D is the smaller than type C, it is divided by endodyogeny, schizogony and produces type E, which occurs 3-15 days after infection. Type E multiplying by schizogony and it resembles with type D. Later type E produce male and female gametes by the process of gametogony. These gamonts occur throughout the small intestine and are common in the ileum 3-15 days after infection. Oocyst formation occurs in the epithelial cells of the small intestine after fusion of male and female gametes. Oocysts are discharged from the epithelial cells and expelled out with faeces. In this case the prepatent period is three to five days and peak oocyst production occurs between five to eight days. After feeding sporulated oocysts the prepatent period in cats is 21-24 days and after feeding tissue containing tachyzoites is 9-11 days.

Extra-intestinal cycle- This type of life cycle mostly occurs in extra-intestinal tissue of non felines species like mammals and avian host but they may also occur in the cat. The extra-intestinal life cycle in intermediate host may start after the ingestion of sporulated oocyst or by tissue containing bradyzoites or by tissue containing tachyzoites.

Later different organs of the intermediate host are infected via blood circulation. In the definitive host extra-intestinal cycle may start almost simultaneously with the enteroepithelial cycle of development. There are two developmental stages found in extraintestinal development.

1. Tachyzoite or endozoites is a rapidly multiplying form during acute infection.
2. Bradyzoites or cystozoites is a slow multiplying encysted form, which is seen in chronic infection.

Tachyzoite or endozoites formation- This tpe of infection is seen especially in acute visceral infection. In cats this type of development occur in mesenteric lymph nodes and other organ which is coexistent with the enteroepithelial cycle. In other animals tachyzoites infection occur by ingestion of sporulated oocyst or infected meat of other intermediate host. It develop in a vacuole in various type of cells, including fibroblasts, hepatocytes, reticular cells and myocardial cells. In this case organisms multiply by endopolygeny or schizogony. About 8-16 organisms are accumulated in a host cell after division. Later which infect to new cells. The accumulation of tachyzoites cells is called terminal colonies aggregates or pseudocysts.

Bradyazoite or cystozoite formation- Bradyzoites contained in cysts are characteristic of chronic infection and occur mainly in the brain, heart and skeletal muscle. Bradyzoites multiply slowly by intracellular endodyogeny. Cysts may measure up to 100um in diameter and contain up to 60000 organisms. Bradyzoites resist peptic and tryptic digestion. Oocyst, which are infected from oral rute or subcutaneously or intra peritoneal are more infective than tachyzoites and bradyzoites in cysts.

Toxoplasmosis in cats - Cats play and important role in the epidemiology of toxoplamosis. Generally cats are commonly infected in nature and produce million of oocyst but rarely produce clinical diseases. In cat toxoplasmosis causes enteritis, enlargement of mesenteric lymph nodes, pneumonia, perivascular and degenerative changes in the central nervous system, encephalitis, diarrhoea etc.

Toxoplasmosis in dogs – In dog toxoplassmosis causes fever, anaemia, respiratory distress and haemorrhagic diarrhoea etc. The main pathogenesis are necrotic nodules may be produced in the parenchymatous tissue of lungs, the spleen and liver are usually enlarged and the organisms can be found in the liver. The ulcers in the digestive tract are also produced.

Toxoplasmosis in cattle – The clinical signs in cattle are dyspnoea, caughing, sneezing, a nasal discharge, trembling, shaking of the head and rising of the temperature is also seen in several cases. The main pathogenesis of the cattle is fibrinous deposition in the peritoneal cavity, enlargement of sub maxillary and branchial lymph glands, and haemorrhagic tracheitis and pneumonia with consolidation and in chronic form the blood vessel wall is calcified.

Toxoplasmosis in sheep – The main symptoms of the disease in sheep is abortion. The severity of congenital infection depends on the duration of gestation at time of infection. Infection early in gestation (e.g. 45-55days) causes death of the foetus and infection at a later time of gestation (90 days) causes other serious symptoms of the disease. Infection at 120 days of gestation causes faetal infection but death is not occurs.

Toxoplasmosis in pigs – Usually young pigs are affected by this disease and symptoms are fever, shivering, weakness, coughing relaxation of abdominal muscles and dirrhoea. The most common post-mortem signs are pneumonia, necrosis of the liver cell, bydrothorax, ascites, lymphadenitis, enteritis etc.

Toxoplasmosis in birds – A large number of records have been made concerning the prevalence of Toxoplasma infection in birds. In fowls the symptoms are anorexia, emaciation, diarrhoea, blindness, sometime death also occur without any evidence of previous illness. Histopathological symptoms shows pericarditis, diffuse myocarditis, a necrotic hepatitis and also ulcers are found in the gastrointestinal tract, some time active follicles develop in the bursa of Fabricius.

Toxoplasmosis in man – The common symptom of the toxoplasmosis is abortion. Most of the cases of toxoplasmosis in children are congenital in origin, the mother usually shows a mild infection or no infection. Maternal to fetal transmission of parasites occurred less commonly early in pregnancy than later but the severity of the damage to the fetus was greater with early infection than later. In severe infections acquired early in pregnancy causes abortion. In less severity infections the pathogenesis are mostly found in central nervous system than in the visceral and somatic tissues. The main lesions are cerebral calcification, choroido-retinitis, hydrocephalus and psychomotor disturbances. The child may be either alive or death, and if born alive may suffer serious mental retardation within a few week of birth.

Acquired toxoplasmosis (i.e., non-congenital) is suspected when lymphandenopathy, lassitude accompanied by fever, lymphocytosis, eye lesions of doubtful origin or myocarditis etc are observed. The transmission from infected meat is very rare.

Public health significance of toxoplasmosis – Transmission by the cat is an important factor in the epidemiology of the infection. The role of non- cat transmission (e.g., by meat) has not yet been fully confirmed. In Britain a study shows that the general prevalence of toxoplasmosis was 25% of the adult population. The prevalence increases up to the age of 20 years. Preventive aspects for pregnant women should stop to play with cat, washing of hands before eating, gloves should be worn when gardening and uncooked meat should not be fed to cats.

Treatment- No completely satisfactory treatment for toxoplasmosis is known.

1. A combination of sulphadiazine (120mg/kg b. wt.) and pyrimethanmine (1mg/kg b. wt.) given orally has reduce the oocyst shedding of Toxoplasma in cat.
2. Intramuscular injection of 2mg/kg b. wt. pyrimethamine with 100mg/kg b. wt. sulphadiazine inhibited oocyst shedding.

 

 

Neospora caninum

 

It is a recently recognized protozoal infection of dogs and, experimentally of rodents and cats. Neospora caninum is an obligate intracellular parasite that has been confused previously with T. gondii. Only sexual stages are known and thus resemble with T. gondii. The complete life cycle on N caninum is unknown, but it can be transmitted transplacentally in dogs and subsequent litters may be affected.

 

The tachyzoites are 5-7 by 1-5 µm in diameter, depending on the stage of division. They divide by endodyogeny. Tachyzoites are found in myocytes, neural cells, dermal cells, macrophages and other cells. They are often located directly on the host cell cytoplasm without vacuole. Tissue cyst up to 10 µm in diameter are found in neural cells, the cyst wall is amorphous and up to 4 µm thick. Cysts have no septa, and enclose slender 7 µm by 1.5 µm in diameter of the bradyzoites.

Life Cycle

Dogs and coyotes (confirmed) and other wildlife carnivores (suspected) serve as definitive hosts with fecal oocyst shedding. This shedding of oocysts is usually of short duration and few oocysts are shed compared to Toxoplasma gondii. In some circumstances however, shedding may continue for up to 4 months. Dogs / coyotes are infected when they feed on tissues of an infected intermediate host, normally cattle (bovine foetal membranes and raw meat). Most dogs infected this way shed oocysts but do not usually develop a systemic infection, may not seroconvert and rarely show clinical signs. A few animals may develop systemic infection and they become sub-clinically infected. Trans-placental infection in these sub-clinically infected animals is common with many pups in these litters being infected, but abortion is rare. Successive litters from the same subclinically infected bitch may be born infected, but possibly at a reduced rate. However, post natal infections following recrudescence of sub-clinical infections following an immunosuppressive incident (steroids, MLV vaccination, illness etc) are being reported with increased frequency. Tachyzoites and tissue cyst forming bradyzoites compose the intermediate host parasite stages. Neospora tachyzoites occur in large cultures of 20-40 organisms and this accounts for the severe necrosis and florid inflammatory infiltrates commonly observed in skeletal/cardiac muscle and other visceral organs. This contrasts the usually less florid inflammatory reaction to Toxoplasma gondii tachyzoites, which are usually present in lesser numbers. Tissue cysts are found principally in the CNS but have also been reported in the skeletal muscles of naturally infected dogs and cattle.

Clinical findings – Both pups and older dogs are affected. Not all littermates are affected. Most severe infections are in young pups and typically evident as ascending paralysis of limbs particularly hind limbs. The paralysis is often progressive and results in rigid construction of the muscles of affected limbs. In some dogs, only neural signs are observed. The syndrome of polyradiculoneuro myositis appears typical of neosporiosis. Ulcerative dermatitis, hepatitis, pneumonia and encephalitis may also occur.

 

Lesions – Non suppurative encephalomyelitis, polyradiculoneuritis, acute necrotizing myositis, phlebitis, multifocal/coagulative hepatic necrosis, and atrophy of muscles are predominant findings.

Diagnosis

Live animal

• Serology: the indirect fluorescent antibody test (IFAT) is the most commonly employed serological test measuring antibodies to N. caninum. Titres > 1:50 indicate exposure but not necessarily disease. Titres > 1:800 in a dog with clinical signs is strong supporting evidence of neosporosis.

• PCR on cerebrospinal fluid (CSF) is being used with increased frequency as a confirmatory diagnostic test.

• Immunohistochemistry (IHC) on muscle biopsies or skin biopsies (in cases with skin involvement), collected into 10% buffered formalin, is a confirmatory test.

• Fecal floatation procedures have very poor sensitivity due to short duration of fecal shedding and low numbers of oocysts shed.

Post Mortem

• Histopathology enables visualization of the characteristic pathology associated with N. caninum.

• IHC on formalin-fixed tissues (muscle, spinal cord, brain) are used to confirm the diagnosis.

Treatment

• Clindamycin 11-22mg/kg BW or

• Potentiated sulphonamides (15mg/kg BW) + Pyrimethamine (Daraprim 25mg® – 1mg/kg once daily) Treatment should be continued until the animal has fully recovered or until no further clinical improvement is observed (2-9 weeks).

Supportive treatment (non-steroidal antiinflammatory drugs (NSAIDs), low dose corticosteroids, nursing care) are also beneficial.

Control and Prevention

Trans-placental transmission is the most important and most common route of infection of puppies. The number of puppies infected per litter varies from none to all with an average of about 20% of the litter. Less than 50% of infected pups will develop clinical signs. Transmission can occur repeatedly over several infected litters. Preventative treatment of bitches during pregnancy or of seropositive apparently normal littermates of clinical cases, to block pre-natal infection of pups, has proven unsuccessful. Therefore, bitches that produce infected litters should be sterilized and removed from any breeding program. Bitches with high antibody titres (>1:800 on IFAT) are more likely to produce infected pups. Serological screening of bitches in a breeding facility can be used to identify high risk bitches which should then be sterilized and removed from the breeding program Post natal infection occurs, although it is still not known whether disease in adult dogs is due to a recent infection or a relapse of a congenital infection. Canines frequently acquire the infection through ingestion of infected material especially from bovine fetal membranes or raw meat. This results in oocyst shedding but these dogs do not normally develop a systemic infection. In breeding facilities all meat fed should be thoroughly cooked, any access to bovine placentas must be avoided and fecal management to reduce the risk of fecal contamination of feed and water sources should be practiced.

 

 

 

 

 

Family- Theileriidae

 

Genus- Thileria

Species- parva

Location and Host- This parasite is found in the RBC, lymphocytes and histiocytes of the cattle of East, Central and South Africa and India etc. The vector of this parasite is Rhipicephalus appendiculatus, but other species of Rhipicephalus and Hyalomma  transmit it. 

Morphology- Two forms of parasites are found in cattle. The form which are found in RBC are mainly rod –shaped, 1.5- 2µm by 0.5-1µm in diameter, some time round, oval, comma and ring shaped forms may also occur. In the forms which are found in RBC, there is no evidence of multiplication.

The actively multiplying forms of parasite occur chiefly in the cytoplasm of lymphocytes and occasionally, in the endothelial cells, especially of the lymphatic glands and the spleen, these are called schizonts or Koch’s blue bodies. The shape of schizont which is actively multiplying are circular or irregular shaped and measure about 2µm to 12µm in diameter. Two forms of schizonts are recognized. The schizonts which contain large chromatin granules 0.4-2µm in diameter are called macroschizonts and produces macromerozoites. The other form contains smaller chromatin granules, 0.3- 0.8µm in diameter are called microschizonts and produce micromerozoites. Later they invade the red blood cells and may represent sexual stages of the parasites.

Life cycle –

In cattle – When the cattle is infected by infected tick vector then a large number of sporozoites are released in the blood of that cattle. The transmission to the animal does not occur immediately on attachment but sporozoites develop in the salivary gland during the first two to four days of engorgement of nymph or adult stages. After the infection of sporozoites the first visible stages occur in the lymph nodes 5 to 8 days after infection. The first visible stages are small rounded bodies with round nucleus. Schizogony of the parasite occurs in the lymphoid and reticulo endothelial tissues.  They appear as multinucleated macroschizonts, which is called Koch’s blue bodies. Macroschizonts contain an average of eight nuclei and the release of macro merozoites from macroschizonts is not observed later macroschizont contain 50-120 nuclei. After the formation of macroschizont, the formation of microschizont started. The size of microschizont is smaller than macroschizont and micromerozoites are released and they penetrate the RBC’s of cattle. Later both forms formed micro and macrogamont inside the RBC.

In tick host- After the ingestion of intra erythrocytic stages of parasites by the tick host, lysis of erythrocytes occurs and merozoites are liberated which differentiate into sexual stages. In the lumen of the gut of infected nymphs, spindle-shaped microgamonts develop from ring forms. These break up into several thread-like microgametes after nuclear division and the development of thread like cytoplasmic projections. Ring forms also develop into round forms, which are considered to be macrogametes.

Later both gametes fuse to form zygote. Six days after repletion zygote appear in the epithelial cells of the gut. There is an increase in size and progressively denser cytoplasm occurs up to the third day after moulting to adult ticks. By the fifth day after moulting a club shaped, motile ookinete is produced. The ookinete is pass into the salivary gland which are found only in the glandular secretory cell and round up into sporoblast, inside the sporoblast cell sporonts are form which is by the processes of sporogony. These sporozoites are formed after the fourth day of engorgement by the tick and ultimately infect the new cattle host.

Pathogenicity and symptoms – The disease cause by this parasite is called East Coast fever. It is a serious disease with high mortality in susceptible stock, being characterized by lymphoid hyperplasia, followed by exhausting of the lymphoid tissues and leucopenia. The Zebu (Bos indicus) has a high level of natural resistance. The incubation period following exposure is 10-25days and the acute form of disease is the most common, lasting 10-23days, The main symptoms are high fever, swelling of lymphnodes, nasal discharge, swelling of the eyelids and ears and the diarrhoea with blood and mucus in the faeces. In adult animals the mortality may be 95%. There is no haemoglobinuria because red blood cells are not destroyed in case of T. parva.

Diagnosis- The most satisfactory diagnosis is made by the demonstration of the schizonts in material obtained from superficial lymphnodes or by spleen puncture. The forms in the erythrocytes may be difficult to see at time and in the early part of the infection.

 

Theileria annulata

Geographical distribution- Parasite is mostly prevalence in North America, Middle and Far East, Russia and Southern Europe, Iran, Nepal, India, Japan, Korea, Siberia. It is a highly fatal disease of cattle in North America and trasmitted by Hyalomma species of tick.

Location and host- Parasites are mostly found in the RBC and lymphocytes of the spleen and lymph node of cattle and buffalo.

Morphology- The parasite in the red blood cells are mostly round, oval or ring shaped and it measures about 0.5-1.5um in diameter. Sometimes rod shape, commas and anaplasma like structure may also found. The erythrocytic forms undergo binary fission with the formation of two daughter individuals, in case of T. annulata it is the important method of multiplication. Macroschizonts and microschizonts are found in the lymphocytes of the spleen and lymph nodes, being similar to those of T. parva. Theileria annulata is easily transmissible by blood passage and schizonts are found in numerous in the circulating blood.

Life cycle- The development of life cycle in the vertebrate host is related to that of T. parva and in T. annulata intraerythrocytic division is the most important method of multiplication but the organisms are also propagated in lymphoid cells.

The tick vector of this parasite is the various species of the genus Hyalomma. In india H. savignyi (Syn. H .marginal) acts as the vector of T. annulata in India and Middle East. H. dromedarii in central axis. There are two forms of erythrocytic stages, which represent the gamonts. After ingested the infected RBC by the tick, gamonts of the RBC produce male and female gametes. In the gut of the ticks male and female gametes are fused and zygote is formed. The size of zygote is increase and reach about 10µm at 12days of infection. At 13days after division of the nucleus a club shaped form is produce, which is called ookinete. These ookinete pass in the acinar cells of the salivary glands (types II & III) of tick where spozoites are formed by the process of sporogony, later sporozoite are release and mixed into saliva. The new hosts are infected during engorgement by the infected tick.

Pathogenesis and symptoms- More pathogenic strains of this parasite occurs in India, Iran Russia and Israel, mortality rate reach up to 90% in some cases. The acute form of disease occurs in all breed and all ages of cattle as well as buffalo and zebu. The incubation period is 9-25days and the acute form of disease may last from three days to 20days. The symptoms are a marked rise of body temperature reaching 40-41⁰C, is followed by depression, lacrimation, a progressive chronic anaemia is common, nasal discharge and swelling of the superficial lymph nodes. Emaciation is rapid and haemoglobinuria may occur. The postmortem finding shows a marked enlarged spleen and liver. The lungs are usually oedematous and lymphnodes may be swollen specially in the acute form of disease.

Diagnosis – It is based on the demonstration of parasites in the red blood cells or in smear of material obtained from lymphnodes or spleen. Differentiation between T. annulata and T. parva is not easy and diagnosis is based on the evaluation of the enzootic parasitic conditions in the area.

Treatment- Oxytetracycline and chlortetracycline- 5-10mg/kg b.wt. I/M.

Parvaquone –  20mg/kg b.wt. single dose I/M, or 10mg/kgb.wt. given 48hrs.apart.

 

Theileria lawrenci

Geographical distribution-Parasites are distributed in East and Central Africa, Angola.

Location and host- Parasite is mostly found in the RBC of cattle and water buffalo and vectors are ticks such as Rh. appendiculatus and possibly R. duttoni.

This parasite produces severe and fatal disease in cattle and water buffalo. The disease cause by this parasite is called "Corridor disease". Corridor disease is highly pathogenic and mortality reaches 80%.

 

Theileria mutans

Geographical distribution- This disease is mostly found in Africa, Asia, Australia and Russia.

Location and host- Parasite is mostly found in the RBC of cattle and the different species of ticks act as vector they are Rh. appendiculatus, Rh. evertsi, H. bispinosa, H. punctata, B. annulatus and B. microplus.

Life cycle is same as T. parva.

Pathogenesis and symptoms – High fever and subclinical anaemia may also occur.

 

Theileria of sheep and goat-

Theileria ovis

Geographical distribution- Parasite is mostly endemic Africa, Asia, India, Russia and some parts of the Europe.

Location and host – Parasite is mostly found in the RBC of infected sheep and goat. Different ticks Rh. bursa, Rh. evertsi, D. sylvarum, H. sulcata etc., act as the vector of this parasite.

Lifecycle is similar to T. parva Pathogenesis and symptoms- The pathogenically is mild and there is seldom mortality occur.

 

Phylum – Ciliophora

Class- Kinetofragminophorea

Order-Trichostomatidae

Family- Balantidiidae

Genus- Balantidium

Species- coli

Geographical distribution- Worldwide.

Location and host- Parasites are mostly found in the large intestine of pig, man and monkey.

Morphology- In case of B. coli, there are two morphological structures.

Vegetative form- It is large form and average size of parasite is 50-60µm in length, but some time reach up to 150µm in length and it is easily observed in the stool of infected animals. Body structure is oval in shape and covered by cilia. There are two type of nuclei, the micro-nucleus and mega-nucleus. The mega-nucleus is kidney shape and micronucleus is small rounded shape. Food vacuoles and contractile vacuoles are present in the endoplasm of the body.

Cyst- Cysts are ovoid to spherical shape and measure about 40-60µm in diameter. They are faintly yellowish green in colour, the organism can be recognized within the cyst by the macronucleus.

Reproduction- This parasite multiply by transverse binary fission but conjugation also take place. Transmission to other host is by the cyst.

Pathogenesis and symptoms- The pig acts as a primary host and in pig B. coli is generally regarded as a commensal. Under normal condition it is found in the lumen of the large intestine and is associated with no change in the mucosa. But in heavy infection it may invade the mucosa and cause superficial and even deep ulceration these associated with a mild to severe enteritis. In acute and at the time of fatal infection in pig it causes haemorrhagic dysentery. This parasite is a zoonotic important in human because usually human is infected by pig.

Diagnosis- By finding the cyst or some time also found trophozoite of parasite in faecal examination.

Treatment- Acute infections may be treated with the tetracycline antibiotics.

Oxytetracycine –0.5gm orally

Carbarsone at dose of 250mg is given daily for ten days.

Diiodoquin- 300 mg once daily for 5days.

 

 

Order- Rickettsiales (Rickettsia)

Anaplasma marginale

 

Geographical distribution- Parasite is widely distributed throughout the tropical, subtropical and some temperate areas of the world.

Location and host- Cattle are the major hosts but infections also occur in the RBC of water buffalo, bison, zebra camel, sheep, goat and deer. The vector of this parasite is mainly different species of ticks but stable flies, tabanids and mosquitoes also transmit.

Morphology – Anaplasma appear as small, spherical bodies or sometime filamentous structure may be found and the colour of the parasite is dark red when stained inside the RBC. The size of parasite is 0.2-0.5µm in diameter. Two morphological types of A. marginale are found, a normal rounded form and a filamentus forms, both of which occurred in the majority of infected animals, but some cases only the rounded form is present.

Life cycle- Some 20 species of ticks and blood sucking flies such as tabanids, deer flies, stable flies and mosquitoes transmit this parasite. Carrier cattle play an important role in the epidemiology of infection although, deer have also been demonstrated to serve as carriers for cattle and deer to deer transmission may occur in absence of cattle.

Mechanical transmission of anaplasmosis is well known, and major and minor operations in cattle husbandry such as dehorning, castration, vaccination, blood sampling may be responsible for the transmission of anaplasmosis.

Pathogenesis and symptoms – Anaplasmosis is essentially a disease of adult cattle and in general, severe clinical infections do not occur until an animal is about 18 months of age. In mature cows the incubation period is 15-36 days with an average of 26 days. The main pathogenicity is high fever, anorexia develops and animals show severe anaemia. Mortality rate may reach up to 80%.

Treatment-Tetracyclines (chlortetracycline, tetracycline and oxytetracycline) –6-10 mg/kg b.wt. I/M.

 

Anaplasma centrale

This organism is morphologically similar to A. marginale. As its name suggest because it is placed in the central of the RBC. The infection is milder in comparison to those of A. marginale.

 

Anaplasma ovis

Parasite is mostly found in the RBC of sheep and goat, it is usually non-pathogenic.

 

BOVINE BABESIOSIS

 

 

AETIOLOGY

 

Classification of the causative agent

 

Bovine babesiosis (BB) is a tick-borne disease of cattle caused by the protozoan parasites of the genus Babesia, order Piroplasmida, phylum Apicomplexa. The principal species of Babesia that cause BB are: Babesia bovis, Babesia bigemina and Babesia divergens. Other Babesia that can infect cattle include B. major, B. ovata, B. occultans and B. jakimovi.

 

EPIDEMIOLOGY

 

All Babesia are transmitted by ticks with a limited host range. The principal vectors of B. bovis and B. bigemina are Rhipicephalus spp. ticks and these are widespread in tropical and subtropical countries. The major arthropod vector of B. divergens is Ixodes ricinus. BB is principally maintained by subclinically infected cattle that have recovered from disease. Morbidity and mortality vary greatly and are influenced by prevailing treatments employed in an area, previous exposure to a species/strain of parasite, and vaccination status. In endemic areas, cattle become infected at a young age and develop a long-term immunity. However, outbreaks can occur in these endemic areas if exposure to ticks by young animals is interrupted or immuno-naïve cattle are introduced. The introduction of Babesia infected ticks into previously tick-free areas may also lead to outbreaks of disease.

 

 

Hosts 

A. B. bovis and B. bigemina

1.  cattle

2.  water buffalo (Bubalus bubalis) and African buffalo (Syncerus caffer)

3.  reports of disease in white-tailed deer (Odocoileus virginianus) in Mexico 

B. B. divergens

1.  cattle and reindeer (Rangifer tarandus)

2. Mongolian gerbils (Meriones unguiculatus); other peridomestic rodents are resistant to disease

3.  Splenectomised humans and non-human primates are highly susceptible

4. Experimental infection with no clinical signs have been documented in splenectomised ungulates including mouflon (Ovis musimon), red deer (Cervus elaphus), roe deer (Capreolus capreolus), and fallow deer (Dama dama)

 

Life Cycle and Transmission 

 

BB is principally transmitted by means of ticks

·         Tick vectors of Babesia bigemina: Rhipicephalus microplus (formerly Boophilus microplus) and Rhipicephalus annulatus (formerly Boophilus annulatus); Rhipicephalus decoloratus, Rhipicephalus geigyi, and Rhipicephalus evertsi are also competent vectors  B. bigemina transmitted by feeding of adult and nymphal stages of one-host  Rhipicephalus spp. ticks

·          Tick vectors of Babesia bovis: Rhipicephalus microplus and Rhipicephalus annulatus; Rhipicephalus geigyi is also a competent vector  B. bovis transmitted by feeding of larval stages of one-host Rhipicephalus spp. ticks

·          Tick vectors of Babesia divergens: principal vector is Ixodes ricinus  Ixodes ricinus is a three-host tick with only adult stages feeding on vertebrates (eg. cattle)

·          Babesia sporozoites are inoculated into the vertebrate host by ticks and invade red blood cells (RBCs) where they transform into trophozoites . These grow and divide into two round, oval or pear-shaped merozoites which, in turn, are capable of infecting new RBCs; the division process is then repeated.

·          Babesia parasites can be transmitted transovarially between tick generations; in the case of  Ixodes, surviving up to 4 years without a vertebrate host.

·          Babesia may also be transmitted by fomites and mechanical vectors contaminated by infected blood.

·         Infrequently, calves can become infected in utero

 Sources of infection 

1. Blood infected with Babesia parasites and associated vectors of infected blood (especially ticks, but also by mechanical means)

 

Occurrence

 

 BB is found in areas where its arthropod vector is distributed, especially tropical and subtropical climates. Babesia bovis and B. bigemina are more widely distributed and of major importance in Africa, Asia, Australia, and Central and South America. Babesia divergens is economically important in some parts of Europe and possibly northern Africa.

 

Clinical signs

Babesia bovis

·         High fever

·         Ataxia and incoordination

·         Anorexia

·         Production of dark red or brown-colored urine

·         Signs of general circulatory shock

·         Sometimes nervous signs associated with sequestration of infected erythrocytes in cerebral capillaries

·         Anaemia and haemoglobinuria may appear later in the course of the disease

·         In acute cases: maximum parasitaemia (percentage of infected erythrocytes) in circulating blood is often less than 1%

Babesia bigemina

·         Fever

·         Haemoglobinuria and anaemia

·         Production of dark red or brown-colored urine

·         Nervous signs minimal or non-existent as intravascular sequestration of infected erythrocytes does not occur

·         Parasitaemia often exceeds 10% and may be as high as 30%

Babesia divergens

·         Parasitaemia and clinical appearance are similar to B. bigemina infections

Lesions

·         Lesions observed are those most often associated with an intravascular haemolytic condition

·         Pale or icteric mucous membranes; blood may appear thin and watery

·         Subcutaneous tissues, abdominal fat and omentum may appear icteric

·         Swollen liver with an orange-brown or paler coloration; enlarged gall bladder containing thick, granular bile

·         Enlarged, dark, friable spleen

·         Kidneys appear darker than normal with possible petechial haemorrhages

·         Bladder may contain dark red or brown-colored urine

·         Possible oedema of lungs

·         Petechiae or ecchymoses on surface of heart and brain

 

Differential diagnosis

·         Anaplasmosis

·         Trypanosomiasis

·         Theileriosis

·         Bacillary haemoglobinuria

·         Leptospirosis

·         Eperythrozoonosis

·         Rapeseed poisoning

·         Chronic copper poisoning

 

 

 

 

Class: Sporozoea

Suborder- Haemosporina- development similar to that of coccidian but life cycle is shared by two hosts, schizogony occurs in vertebrates while gametogony and sporogony occur in blood sucking invertebrates.

Family- Plasmodiidae- Macro- and microgamonts develop independently, the zygote is motile. Schizogony occurs in vertebrates and sporogony in invertebrates, and pigment is usually formed in host cell.

Genus- Plasmodium, Haemoproteus and Leukocytozoon.

 

Genus- Plasmodium

This genus contains the malarial organisms of man and other mammals and vertebrates. Schizogony occurs in the RBC and also in the endothelial cells of inner organs while the sexual phase of the cycle occurs in blood sucking insects. For mammalians forms these are anopheline mosquitoes and for the avian forms these are culicine mosquitoes.

Avian Malaria

1. Species with round or irregular gamonts which displace the nucleus of host cell

            P. cathemerium

            P. gallinaceum

            P. juxtanucleare

            P. relictum

            P. graffithsi

2. Species with elongated gamonts which usually do not displace the host cell nucleus

            P. circumflexum

            P. durae

            P. elongatum

 

 

 

Developmental cycle

Infective sporozoites do not enter erythrocytes directly but rather develop as exoerythrocytic forms in cells of the reticuloendothelial system prior to invasion of erythrocytes.

Following the introduction of the sporozoites from infected culicine mosquitoes numerous pre-erythrocytic schizonts are found in the macrophages and fibroblast of the skin near the point of entry. These are referred to as cryptozoites. Merozoites from this first generation of pre-erythrocytic schizonts form a second generation of pre-erythrocytic schizonts-the metacryptozoites. Merozoites from the metacryptozoites enter RBC and other cells of the body and in the later form the exoerythrocytic schizonts. In the case of plasmodium P. gallinaceum, P. relictum and P. cathemerium these other cells are endothelial cells but in the case of P. elongatum and P. vaughani they are cells of the haematopoietic system. In some species of avian plasmodium eg, P. gallinaceum, P. elongatum, the exoerthrocytic developmental stages may be added to by forms which are derived from the erythrocytic cycle. These are known as phanerozoites, being derived from the merozoites of the schizonts in the erythrocytic cycle.

The erythrocytic cycle is initiated 7 to 10 days after infection by merozoites from metacryptozoites and at other times by merozoites form exoerythrocytic schizonts located according to the species in the endothelial or haemopoietic cells. On entering the RBC, the merozoites round off to form a trophozoite. This is a small rounded form containing a large vacuole which displaces the cytoplasm of the parasite to the periphery of the cell. The nucleus is situated at one of the poles, giving the young form- a signet ring appearance when stained by Romanowsky stains. The early trophozoites undergo schizogony to produce merozoites, the number produced depending upon the species of parasites. During the process of schizogony, the parasite takes in the host cell cytoplasm by invagination, haemoglobin is digested and the residual hematin pigment is deposited in granules within the food vacuoles. Apparently, schizogony may continue indefinitely, the length of each cycle of schizogony depending on the species of parasite. The release of merozoites from the schizonts occurs synchronously in the host, and in human malaria this is associated with a paroxysm of fever.

After a number of asexual generation has occurred, some merozoites undergo sexual development with the formation of microgamonts and macrogamonts. Further development of the gamonts can take place only when the blood is ingested by a suitable mosquito.

Development in the mosquito is rapid. Within 10 to 15 minutes the nucleus of the microgamonts divides, and through a process of exflagillation, 6 to 8 long, thin, flagella like microgamonts are extruded from the parent cell. These remain attached to the parent cell for a few minutes lashing actively; they then become detached and swim away to find, and fertilize, the macrogamete. The zygote resulting from fertilization is motile and is called an ookinete. This ookinete penetrates the mid gut mucosa and comes to lie on the outer surface of the stomach, forming an early oocyst about 50 – 60 um in diameter. The nucleus of the oocyst divides repeteadly to produce a very large number of sporozoites. These are about 15 um in length with a central nucleus. Maturation of the oocyst takes a variable period of time depending on the species of parasite, temperature and the species of mosquito; but in general it is 10 to 20 days. When matured, the oocyst ruptures, liberating the sporozoites into the body cavity of the mosquito, and these then migrate all over the body of the mosquito but eventually reach the salivary glands. Here they may lie intracellularly, extracellularly or in the ducts of the salivary glands. They are now infective to a new host, infection occurring when the mosquito takes a blood meal. A mosquito remains infected for its life span, transmitting malarial parasite every time it takes a blood meal.

1. Plasmodium cathemerium

Host- common in passerine birds eg English sparrow

Causes acute fatal disease, gamonts are rounded with rod shape rather coarse pigment granules, and displace the nucleus of the cells. Gamonts and schizonts, about 7 to 8 um in diameter; schizogony, about 24 hours cycle. It is transmitted by several species of culex and aedes.

Spleenomeghaly, hepatomeghaly, anaemia and subcutaneous haemorrhage.

2. Plasmodium gallinaceum

Host- primarily a parasite of domestic fowl in India. Other birds pheasant, goose, partridge and peacock. Can be infected experimentally.

Gamonts, round and possessing pigment granules of relatively large size and few in numbers. Schizonts- round to irregular, produce 8 to 30 merozoites. Both developmental stage causes displacement of the host cell nucleus. Schizogony- 36 hour cycle. Exoerythrocytic stage occurs in the endothelial cells, and the reticulo-endothelial cells of the spleen, brain and liver. Transmitted by aedes.

Pathogenesis- the chicken is particularly susceptible, and even adult birds may suffer a mortality up to 80%. Birds become progressively emaciated as the disease progresses. There is anaemea and spleen and liver enlargement. Paralysis may occur due to massive numbers of exoerythrocytic forms in the endothelial cells of the brain capillaries.

3. Plasmodium juxtanucleare

Host- Domestic chicken in South and Central America. Turkeys have been infected experimentally but not ducks, guinea fowl, pigeon or canary.

Gamonts, round to irregular, relatively small, parasites tends to be in contact with the host cell nucleus. RBC is often destroyed. Schizogony-24 hours cycle. 3-7 usually 4 merozoites produced. Developmental cycle poorly known.

Chickens become listless, weak with anaemia and occasionally CNS involvement may be seen.

Treatment

Many of the compounds which are used for the treatment of human malaria have been developed, initially against species. Chloroquine at the rate of 5 mg per kg, paludrine at the dose rate of 7.5 mg per kg and pyrimethamine at the dose rate of 0.3 mg per Kg are all effective against P. gallinaceum.