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Definition
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It is disease of all species, including man
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It is a specific parasite with definite host cat and has wide range of intermediate hosts
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It is manifested by encephalitis, pneumouia, neonatal mortality and abortions and still births in ewes
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Its major importance is as a zoonosis
Aetiology
Transmission
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Infection in cats occurs due to ingestion of infected meat or sporulated oocyst
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Exposure to cat faeces, or materials contaminated by cat faeces, which contains oocyst
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Exposure to infected tissues and meat containing tachyzoites and bradyzoites
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Congenital transmission
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Through milk and semen
Pathogenesis
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Toxaplasma gondii is an intracellular parasite
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It attacks most organs especially reticulo-enothelial and central nervous systems
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Sporozoites or bradyzoites penetrate and multiply in intestinal epithelium
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Cell destruction occurs
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Released toxoplasma spreads to other organs through blood stream
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Later, the organism localises as tissue cysts
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When immunity fails, cysts rupture, large number of inflammatory cells invade surrounding tissue
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A characteristic granulomatous lesions develops
Clinical signs
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Vary with species and age groups
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Most infection go unnoticed
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In dogs , most common in puppies characterized by neurological signs – diarrhoea or pneumonia
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In cats – most common manifestations are pneumonia, encephalitis and pancreatitis
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In sheep and goats – abortions with necrosis and inflammation in the cotyledons of the placenta
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Congenital infection of lambs and kids with encephalitis
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Not common in cattle and horses
Lesions
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Toxoplasma can be found in macrophages, fibroblasts, smooth muscle cells
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Tissue cysts in brain, liver, kidney and skeletal muscle
Brain
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Diffuse necrotising and non-suppurative infiltration of brain parenchyma
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Lymphocytic cells accumulate within the Robin – virchow spaces
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Toxoplasma tachyzoites found scattered singly or in pairs in the parenchyma
Liver
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Contains large, sharply well defined areas of coagulation necrosis
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Tachyzoites are found in the kupffer’s cells of liver, in cysts or scattered in necrotic and normal tissues
Lungs
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Toxoplasma attack type I and II penumocytes and bronchial epithelial cells as well as macrophages, fibroblasts, endothelial cell and smooth muscle cells
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Grossly, small, grey, tumour like masses
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Lining of alveoli becomes cuboidal or columnar and rich in cells suggesting foetal lung
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Alveoli is filled with large mononuclear cells, leucoytes, and cells lining the alveoli with aggregation of Toxoplasma
Lymph nodes
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Enlarged, firm in consistency and congested
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Extensive coagulation necrosis
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Tachyzoites are found in necrotic areas in endothelial cells or free in tissues
Intestine
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Ulcers, necrosis, granuloma formation
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Organisms are demonstrable in muscularis and in granuloma
Pancreas
Diagnosis
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To detect antibodies in live animals
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Complement fixation test
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Haemagglutinateou tests
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Latex agglutination test
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Indirect fluorescent antibody
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ELISA
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Demonstration of toxoplams in tissue sections
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Isolation of the organism
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Immunostaining techniques
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Participants