Source

Final hosts of T. Gondii are cats and other felines, which acquire the infection, mainly by eating other mammals (especially rodents) or birds, and probably by oocysts from contaminated soil with cat feces, through licking/cleaning. Only felines host the parasite in their intestinal tract, where the sexual stage of the protozoan life cycle occurs, causing the excretion of oocysts in the feces for 10-20 days, rarely more.

The intermediate hosts of T. gondii include sheep, goats, rodents, pigs, cattle, chickens and other birds. All these can be carriers of the infectant stage of T. gondii in the tissues, especially in the muscles and the brain. Tissue cysts remain viable for long periods, possibly throughout the lifetime. Cattle appear to be only minimally affected by natural infection with T. gondii.

Method of transmission

Man can be contaminated by:

• Ingestion of contaminated raw vegetables and water (unfiltered);
• Ingestion of raw, uncooked goat milk;
• Direct contact with cat litter;
• Ingestion of raw or insufficiently prepared meat of sheep or swine, containing cysts, much rarer by beef or horse. Overall, this method of transmission represents about 30-63% of infections. Cysts are destroyed by preparing meat at 67 Celsius degrees or by freezing at low temperatures (-)20 Celsius degrees. They resists at cold up to -7 Celsius degrees and heat, it takes 10 minutes for example at temperatures of 50 Celsius degrees to destroy them.
• Transplacental passage if the maternal infection occurs during pregnancy. The frequency of maternal-foetal transmission varies according to the age of pregnancy as follows: around 25% if the infection occurs in the first trimester of pregnancy, about 54% if the infection occurs in the second trimester of pregnancy and about 65% if the infection takes place in the third trimester of pregnancy.
• The transmission linked to a reactivation of an older gondii infection during the pregnancy period was described only in HIV infected women.
• Much rarer infection can occur by transplant (e.g. cardiac transplant) or blood transfusion.

Risk groups

• Pregnant women – risk of maternal-foetal transmission if the infection occurs during pregnancy;
• Women with diseases affecting immunity (HIV infection, immunosuppressive treatments, etc.) – May reactivate the parasite if they have been infected before they become pregnant.

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