Outbreak of toxoplasmosis in a family and documentation of acquired retinochoroiditis.

An outbreak of toxoplasmosis in one household is described. It demonstrates the potential for a common source infection with Toxoplasma gondii to cause multiple cases. Six of seven members of a household investigated for toxoplasmosis demonstrated high antibody titers consistent with recent infection; five of these members (83%) were symptomatic. The most common manifestations were fever and lymphadenopathy, which developed from seven to 18 days (mean 11 days) after a common source ingestion of infected meat. Since inadequately cooked lamb, pork and beef are probably the most common sources of infection in the United States, outbreaks of multiple cases may occur more frequently than is generally appreciated. As more outbreaks of febrile illnesses are examined, especially in families and closed communities, it is likely that more common source epidemics of toxoplasmosis will be recognized. Retinochoroiditis is an unusual manifestation of adult acquired toxoplasmosis. In the index case in this epidemic the patient manifested vision threatening retinochoroiditis 129 days after infection with toxoplasmosis. He represents the ninth well-documented case of toxoplasma retinochoroiditis associated with adult acquired disease.