Serologic evaluation of cattle inoculated with Toxoplasma gondii: comparison of Sabin-Feldman dye test and other agglutination tests.

Six cows and 6 calves were each inoculated with 100 or 100,000 Toxoplasma gondii oocysts. Serum samples were analyzed, using the Sabin-Feldman dye test (DT), indirect hemagglutination test, latex agglutination test, and the modified direct agglutination test (MAT). Antibody titers in cows were lower than in calves. In the cows, DT titers increased briefly during the first month after inoculation, after which the titers were negative; however, T gondii was isolated from the tissues of 4 cows. Indirect hemagglutination and latex agglutination titers were generally less than 1:256. The MAT titers increased to 1:1,024 during the first month after inoculation. In 5 of the 6 cows, the MAT titers persisted. The 6th cow had a preinoculation MAT titer of 1:2,000 for 3 to 6 months. Therefore, the DT was not useful in serologic surveys for T gondii in cattle; the MAT was the most sensitive test and may be useful in the diagnosis of T gondii infection in cattle.