Toxoplasmosis is an infection caused by a single-celled protozoan parasite named Toxoplasma gondii found throughout the world in humans, mammals, and birds. Cats, the definitive host for T. gondii, usually become infected by eating infected prey, and are the only animal that sheds the organism (as oocysts) in their feces. Animals other than cats are usually infected by ingesting oocysts in the soil or by eating infected animals.
Humans can become infected with T. gondii by one of three main routes: (1) by eating raw or inadequately cooked meat that contains T. gondii cysts (bradyzoites) or by eating uncooked foods that have come in contact with infected meat via, for example, cutting boards or cooking utensils;(2) by inadvertently ingesting oocysts that cats have passed in their feces either from a cat litter box or from soil (for example, from gardening) or by eating unwashed fruits and vegetables; (3) a newly infected woman can transmit the infection to her fetus.
Toxoplasmosis in adults usually does not cause symptoms, or causes only mild, nonspecific symptoms such as fever and swelling of the lymph glands. Therefore, the diagnosis is usually made by testing for antibodies that are produced in reaction to T. gondii infection. However, serious illness can occur when a newly infected woman passes the infection to her unborn fetus. Such an infection can lead to an infant with mental retardation, blindness, or other neurologic disorders. An estimated 400 to 4,000 congenital infections with T. gondii occur in the United States each year. Serious illnesses, including infection of the brain, can also occur in persons who have either old (latent) or new T. gondii infections when they do not have normal immune system function. Such persons include those with human immunodeficiency virus (HIV) infection or congenital immune illnesses, persons taking drugs that decrease immune system function, and persons with some types of cancer.
Effective means of preventing toxoplasmosis are as follows: (1) cook meat fully (internal temperature of 160° F) before eating it; (2) peel or wash fruits and vegetables before eating them; (3) wash hands, kitchen tools, counters, and sinks with soap and water after they have touched raw meat or unwashed fruits or vegetables; (4) clean the cat litter box every day so T. gondii oocysts do not have time to become infectious (one to five days); (5) wear gloves and wash hands after changing cat litter (pregnant women should not change cat litter if at all possible); (6) keep cats indoors so they do not become infected by eating prey; (7) feed cats only commercially prepared cat food, never undercooked or raw meat; and (8) wear gloves when gardening and wash hands after contact with soil and sand with which cats may have had contact.
JEFFREY L. JONES
(SEE ALSO: Communicable Disease Control)
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