Serologic prevalence of Toxoplasma gondii in horses slaughtered for food in North America.

Serum samples from 1788 horses slaughtered for food in North America were tested for antibodies to Toxoplasma gondii using the modified direct agglutination test (MAT). Antibodies to T. gondii were found by the MAT in 124 (6.9%) of 1788 sera; the titers were 1:20 (69 horses), 1:40 (37 horses), 1:80 (9 horses), and > or =1:160 (9 horses). A total of 339 selected horses were also tested by the Sabin-Feldman dye test (DT). Dye test antibodies were found in 54 horses with titers of 1:10 (29 horses) 1:20 (12 horses), 1:40 (4 horses) and 1:80 (9 horses). There was no correlation between the DT and the MAT.