Toxoplasma gondii

It is a protozoan parasite. There are multiple ways of acquiring infection. Food and water contaminated with cysts containing bradyzoites (a stage in the life cycle of Toxoplasma) can lead to infection. Eating undercooked pork, lamb, shellfish etc and drinking unpasteurised goat’s milk (contains tachyzoites) can cause the disease. It infects cats which in turn can pass on to humans. Oocysts in cat feces spread the infection. You will often come across clinical vignettes talking about “cleaning the cat litter box” which is often a hint to Toxoplasmosis! A woman who gets infected close to pregnancy can pass on the infection to her child. Rarely, blood transfusions and organ transplants can cause Toxoplasmosis.

Clinically, it presents with fever, flu like symptoms and lymphadenopathy. Congenital toxoplasmosis presents with microcephaly, seizures, chorioretinitis, intracranial calcifications, blindness and maculopapular rash. It can cause stillbirths and miscarriages. In immunocompromised individuals it presents as encephalitis, intracranial mass lesions, myocarditis and pneumonitis. Diagnosis is made by the demonstration of trophozoites by Giemsa stain in smears from CSF, bone marrow etc. IgM and IgG by ELISA, indirect immunofluorescence, CFT, indirect haemagglutination tests can be used. PCR can be done in amniotic fluid.