Submitted to: American Journal of Veterinary Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 9/12/1996
Publication Date: N/A
Interpretive Summary: Infection by the protozoan parasite, Toxoplasma gondii causes mental retardation and loss of vision in children and abortion livestock. Humans become infected with T. gondii by ingesting infected meat, by ingesting food and water contaminated with oocysts from feces of infected cats, or congenitally. Infected pigs are considered as an important meat source of Toxoplasma for humans. Serologic examination is an effective way of diagnosing of toxoplasmosis in pigs. Scientists at the Beltsville Agricultural Research Center report antibody responses of pigs experimentally infected with T. gondii. They found that pigs inoculated with few (10 or less) T. gondii oocysts became infected and developed antibodies. These results will be of interest to public health workers, veterinarians and diagnosticians.
Technical Abstract: Sera from pigs inoculated with oocysts were examined for T gondii antibodies by various serologic assays. Pigs (n=42) were inoculated orally with 10 (14 pigs), or 1 (28 pigs) infective oocysts and 6 pigs served as uninoculated controls. Blood-serum samples were obtained at 1 to 3 week intervals until euthanasia. At necropsy, brains, hearts and tongues of pigs were bioassayed in mice and cats for isolation of T gondii. The modified agglutination test (MAT) using whole fixed tachyzoites and mercaptoethanol, the latex agglutination test (LAT), the indirect hemagglutination test (IHAT), the Sabin-Feldman dye test (DT), and the ELISA were used to evaluate serologic responses to T gondii. Toxoplasma gondii was isolated from tissues of 13 of 14 pigs each fed 10 oocysts, 17 of 28 pigs each fed 1 oocyst, and 0 of 6 control pigs. Twenty-nine of 30 T gondii infected pigs developed antibodies when measured by the MAT, DT, and ELISA; the 1 seronegative, infected pig had been fed 10 oocysts and was euthanatized 69 days postinoculation. The LAT detected antibodies in 26 of 30 infected pigs. The IHAT detected antibodies in 11 T gondii-infected pigs. The MAT, DT, and ELISA were more sensitive serologic assays than LAT and IHAT for detecting antibodies induced by low numbers of T. gondii in pigs.