PREVALENCE OF TOXOPLASMA-GONDII IN CANADIAN MARKET-AGE PIGS

During 1991 and 1992, 2,800 market-age pigs were sampled at federally inspected abattoirs from across Canada. Anti-Toxoplasma gondii IgG at titers of greater than or equal to 1:32 were found in 240 pigs examine d by a commercial, latex agglutination test. Seroprevalences ranged fr om 3.5 to 13.2% in the different regions of the country. Tissue hybrid ization studies using a previously developed probe demonstrated T. gon dii ribosomal RNA in 9 of 36 animals, whereas mouse bioassay testing o f heart muscle and diaphragm from all 2,800 pigs failed to demonstrate the presence of infective stages of T. gondii in tissues. Although se rology results from this study indicated that Canadian market-age pigs are infected with T. gondii at rates similar to those reported from o ther parts of North America, mouse bioassay results suggested that Can adian pork products contain low levels of infective organisms. This ap parent discrepancy suggests that serological evidence of T. gondii inf ection in pigs alone does not accurately assess the public health risk s associated with consuming improperly cooked pork products.