Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: April 20, 1997
Publication Date: N/A
Interpretive Summary: Infection by the protozoan (single celled) parasite Toxoplasma gondii is widespread in livestock and humans in the U.S. Ingestion of tissue cysts in undercooked, infected meat and ingestion of food or water contaminated with the resistant form of Toxoplasma (oocysts) from cat feces are the 2 principal ways humans acquire T. gondii infection. Pork is considered the major meat source of T. gondii in the United States. In a national swine survey, T. gondii antibodies were found in 23% of 11229 market pigs and 42% of 613 adult pigs that were slaughtered for food in 1983-1984 (Dubey et al., 1991). These data were based on measuring antibodies to T. gondii in a 1:25 dilution of serum using the modified agglutination test (MAT). The cut-off titer of 1:25 was selected arbitrarily because, at the time, there were no data on the specificity and sensitivity of the various serologic tests for detection of latent T. gondii infection in swine. A scientist at the Beltsville Agricultural Research Center has determined that the MAT is specific for toxoplasmosis in pigs because this test did not cross react with sera from swine infected with other protozoa, helminths, and viruses. These results will be useful to diagnosticians and veterinarians.
Technical Abstract: Serum samples from Toxoplasma gondii-negative pigs infected with protozoa, helminths and viruses, and from fetal pigs were examined for cross reacting antibodies to T. gondii by the use of the modified agglutination test (MAT). Nonspecific reactions with T. gondii antigen were not found in 1:10 dilutions of sera from 8 pigs experimentally infected with Sarcocystis miescheriana, 11 pigs infected with Ascaris suum, 3 pigs infected with Trichuris suis, 10 pigs infected with Trichinella spiralis, 9 pigs infected with various porcine viruses, 6 gnotobiotic pigs, and 82 fetal pigs. Antibodies were also not found in 1:25 dilution of sera from 200 naturally aborted fetal pigs. Thus, evidence for cross reactivity to T. gondii with unrelated or related organisms using the MAT was not found.