Toxoplasmosis.

Recent research has shown that Toxoplasma gondii, the cause of human toxoplasmosis, is a protozoan close to the genus Isospora, whose life cycle involves cats as the definitive host, and other mammals, including man, and birds as intermediate hosts. Cats shed oocysts in their faeces; these are infective to the intermediate hosts when ingested. But the non-felid intermediate hosts can also become infected by eating other intermediate hosts. Probably most human infections occur in this manner and result from eating raw or insufficiently cooked meats. Most people become infected during their life time, but most infections are benign and unnoticed. Occasionally the disease picture may simulate infectious mononucleosis. However, in intrauterine or neonatal infections the disease may be most severe and chorioretinitis, encephalomyelitis, hydrocephalus or microcephaly may result. Diagnosis depends upon demonstrating the parasite in biopsy material or through changing titres in serological tests.