An infection with the protozoan intracellular parasite Toxoplasma gondii .

Causes, incidence, and risk factors

Toxoplasmosis is found in humans worldwide, and in many species of animals and birds. The cat is the definitive host of the parasite. Human infection results from ingestion of contaminated soil, careless handling of cat litter, ingestion of raw or undercooked meat (lamb, pork, and beef), transmission from a mother to a fetus through the placenta (congenital infection), or by blood transfusion or solid organ transplantation. Over 80-90% of primary infections produce no symptoms. The incubation period for symptoms is 1 to 2 weeks. Congenital toxoplasmosis is caused by infection with Toxoplasma gondii in a pregnant woman, with up to 50% of such infections transmitted to the fetus. Signs of congenital infection may be present at birth or develop over the first few months of life. Infants may show signs of central nervous system disorders, enlargement of the liver and spleen, blindness , and mental retardation . Toxoplasmosis also affects people who are immunosuppressed (as a result of AIDS , cancer , or immunosuppressive therapies). The disease may affect the brain, lung, heart, eyes, or liver.

Signs and tests

Tests to determine infection or presence of cysts :

Treatment

No treatment is indicated in asymptomatic people, except children, to prevent retinal inflammation. Treatment of women in pregnancy is controversial because of the toxicity of the medications, but treatment is still advocated. Medications to treat the infection include: pyrimethamine, sulfonamide drugs, folinic acid, clindamycin, and trimethoprim-sulfamethoxazole. Treatment in AIDS patients is continued indefinitely, because the infection may reactivate if treatment is discontinued.

Expectations (prognosis)

Acute infection in children may cause retinochoroiditis (inflammation of the retina ). Toxoplasmosis in adults has a good prognosis (probable outcome) if the immune system is healthy. Chronic asymptomatic infection is usually benign .

Complications

Calling your health care provider

Call for an appointment with your health care provider if symptoms of toxoplasmosis occur. Urgent or emergency conditions exist if the disorder occurs in an immunosuppressed person or in a baby, or if confusion , seizures , or other severe symptoms develop.

Prevention

Avoid undercooked meats, or freeze meat to -20 degrees Celsius for 2 days. Protect children's play areas from cat and dog feces. Wash the hands thoroughly after contact with soil that may be contaminated with animal feces. Pregnant women should have their blood examined for Toxoplasma antibody -- and those with negative results should take measures to prevent infection by avoiding exposure to cat feces (including not cleaning litter boxes), cooking meat thoroughly, and washing hands thoroughly after handling raw meat. Patients with HIV disease should have toxoplasma antibody titers checked. If the results of the blood test are positive and if the CD4 count is less than 200, patients should be given prophylactic antibiotics (trimethoprim-sulfamethoxazole is the medication of choice).