People can develop toxoplasmosis from ingesting soil contaminated by cat feces or eating undercooked meat containing the tissue stages (i.e., bradyzoites, tachyzoites). However, a more serious clinical condition occurs when an unborn child is infected with Toxoplasma in utero. Toxoplasmosis is also a serious disease in immunocompromised individuals, particularly those with AIDS. Infection of humans has also been recorded after organ transplantation, but this is rare.
The public health significance of cats as a source of human Toxoplasma infection has been overemphasized in the past, and food-borne transmission has been recognized as the main source of infection in humans. Many researchers have shown that cat ownership is not associated with testing positive for Toxoplasma. Many animals can be infected with Toxoplasma gondii, and it has been shown that humans are more likely to be infected from eating raw or poorly cooked meat than contact with a cat.
Toxoplasmosis is one of the top three causes of food-borne disease in the United States. Approximately 50% of Toxoplasma cases are transmitted by food. Toxoplasma infection is 1 of 5 infectious diseases causing greater than 90% of food-related deaths.
Toxoplasmosis remains a common parasitic infection of humans and other animals, but fortunately clinical disease is relatively uncommon. However, in addition to the risks to pregnant women, it has emerged as one of the major opportunistic infections in immunocompromised people, especially those with AIDS. In addition, it is thought that the risks of clinical toxoplasmosis will increase as host susceptibility declines" because of disease and an aging society.
Although the risk of acquiring toxoplasmosis from freshly passed cat feces appears to be low, it has been recommended, particularly for high-risk groups (i.e., pregnant, immunocompromised), that gloves be worn when cleaning cat litterboxes and that litterboxes be cleaned daily to ensure that shed oocysts do not have time to sporulate and become infective (taking greater than 24 hours). To reduce the chance of developing toxoplasmosis, high-risk groups should minimize direct handling of raw meat and ensure that meat is thoroughly cooked before consumption. Cats shed oocysts for only a relatively short period (approximately 2 weeks). After they are passed in a cat's feces, 2 to 5 days are required for the oocysts to sporulate and become infective to humans and other animals.
More information on Toxoplasmosis can be found at the following links:
Feline Advisory Bureau
http://www.fabcats.org/cat_group/policy_statements/toxo.html
CDC- Division of Parasitic Diseases informational webpage fact sheet
http://www.cdc.gov/ncidod/dpd/parasites/toxoplasmosis/factsht_toxoplasmosis.htm
A nice schematic of Toxoplasmosis life cycle
http://www.dpd.cdc.gov/dpdx/HTML/Toxoplasmosis.htm
