Serologic diagnosis of toxoplasmosis in cats fed Toxoplasma gondii tissue cysts

Serum samples derived from 7 cats 3 to 950 days after cats were fed tissue cysts of Toxoplasma gondii were evaluated using Sabin-Feldman dye, modified agglutination, indirect hemagglutination, and latex agglutination tests. The modified agglutination test, using whole formalin-preserved tachyzoites, was more sensitive for diagnosis of toxoplasmosis than were other tests. Titers from the modified agglutination test that used formalin-preserved tachyzoites were higher than those from the modified agglutination test that used acetone-preserved tachyzoites. Although cats had no clinical signs of toxoplasmosis, T gondii antibody titers remained high (greater than 1:1,000) for up to 29 months.