A butcher develops a questionable habit of eating various kinds of raw, ground meat over several years. He eventually starts suffering from fatigue and lymphadenopathy. In his extensive physical examination, intensely white focal retinal lesions with vitritis are observed. Chorioretinitis is diagnosed, even though an older laboratory test, the Sabin-Feldman dye test, is found positive. This patient is found to be infected with which of the following?

Toxoplasmosis is generally a mild, self-limiting disease; however, severe fetal disease is possible if pregnant women ingest Toxoplasma oocysts. Consumption of uncooked meat may result in either an acute toxoplasmosis or a chronic toxoplasmosis that is associated with serious eye disease. Most adults have antibody titers to Toxoplasma, and thus would have a positive Sabin-Feldman dye test. The Sabin-Feldman dye test measures antibodies that render the membrane of living T. gondii impermeable to methylene blue (no staining occurs). It is being replaced by IFA and ELISA tests. While we usually think of in utero infections of a developing fetus and the subsequent medical difficulties of the newborn infant, an equally important source of human exposure is raw or undercooked meat in which infective tissue cysts are frequently found. When a tissue cyst ruptures, numerous bradyzoites are released and grow, causing chorioretinitis, myocarditis, and polymyositis. Treatment is with pyrimethamine and sulfadiazine. Schistosomiasis is caused by blood flukes whose cercariae (larvae) penetrate skin in snail-infested water. Trichinosis is caused by the trichina worm whose larvae are found in uncooked pork. Cutaneous larva migrans consists of subcutaneous migrating larvae of hookworms. Visceral larva migrans is a condition in humans caused by the migratory larvae of certain nematodes, humans being a terminal host. Nematodes causing such zoonotic infections are Toxocara canis, Toxocara cati, and Ascaris suum. Larva currens is an itchy, cutaneous condition caused by infections with Strongyloides stercoralis that intermittently comes and goes every few hours.