infectious diseases
Toxoplasmosis
Key Points
T. gondiireproduces sexually in the intestinal tract of cats; most human infections result from direct or indirect contact with cat feces but can be acquired transplacentally or by ingestion of poorly cooked meat that contains cysts. About 11% of the US population have been infected withT. gondii, but symptomatic disease is rare and occurs mainly in fetuses who are infected when the mother acquires acute infection during pregnancy and transmits the infection transplacentally or in people who are immunocompromised by HIV or other causes. Acute infection is usually asymptomatic in immunocompetent patients, but 10 to 20% have manifestations, similar to those of mononucleosis, including lymphadenopathy. Immunocompromised patients typically present with encephalitis and have ring-enhancing intracranial mass lesions, seen on MRI or CT with contrast. To diagnose, use serologic tests (for IgG and IgM antibodies), histopathology, or polymerase chain reaction. Treatment is indicated mainly for congenitally infected neonates, pregnant women with acute infection, and immunocompromised patients. Usepyrimethamineandsulfadiazineplusleucovorinor, if the patient is allergic to sulfonamides orsulfadiazineis not tolerated,pyrimethamineandclindamycin. Pyrimethamineis a potent teratogen and should not be used during the 1st and early 2nd trimester of pregnancy; spiramycin is recommended then for maternal infection. Antiretroviral therapy should be optimized in patients with AIDS; suppressive treatment is continued until patients are asymptomatic and CD4 cell counts are > 200/mcL for > 6 months. 