ARS | Publication request: Endemic toxoplasmosis in pigs on a farm in Maryland: Isolation and genetic characterization of toxoplasma gondii.

Submitted to: Journal of Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: June 23, 2007
Publication Date: February 1, 2008
Citation: Dubey, J.P., Hill, D.E., Sundar, N., Velmurugan, G.V., Bandini, L.A., Kwok, O.C., Pierce, V., Kelly, K., Dulin, M., Su, C. 2008. Endemic toxoplasmosis in pigs on a farm in Maryland: Isolation and genetic characterization of toxoplasma gondii. Journal of Parasitology. 94:36-41.

Interpretive Summary: Toxoplasma gondii is a single-celled parasite of all warm-blooded hosts worldwide. It causes mental retardation and loss of vision in children, and abortion in livestock. Cats are the main reservoir of T. gondii because they are the only hosts that can excrete the resistant stage (oocyst) of the parasite in the feces. Humans become infected by eating undercooked meat from infected animals and food and water contaminated with oocysts.Toxoplasmosis causes mortality in many species of animals in the zoos, especially primates. Scientists at the Beltsville Agricultural Research Center and the Maryland Department of Agriculture report high prevalence of Toxoplasma in pigs on a farm in Maryland. The results will be of interest to biologists, parasitologists, and veterinarians.

Technical Abstract: The prevalence of Toxoplasma gondii was investigated on a poorly managed pig farm in Maryland. Serum and tissue samples from 48 of the 100 pigs on the farm were available for T. gondii evaluation. Serology was evaluated using both ELISA and the modified agglutination test (MAT). Antibodies were detected by ELISA in 12 of 48 animals, while antibodies to T. gondii were found in 36 of 48 pigs with the MAT titers of 1:10 in 5, 1:20 in 2, 1:40 in 5, 1:80 in 7, 1:160 in 5, 1:320 in 4, 1:640 in 4, and 1:1,280 in 4. Hearts of 16 pigs with MAT titers of 1:10 or higher were bioassayed for T. gondii in cats; 11 cats shed T. gondii oocysts. Hearts of 22 pigs were autolysed and bioassayed only in mice; T. gondii was isolated from 3 of these 22 pigs. Genetic typing of the 14 T. gondii isolates using the SAG1, SAG2, SAG3, BTUB, GRA,6 c22-8, c29-2, L358, PK1, a new SAG2 and Apico loci revealed 4 genotypes; 10 isolates belong to Type II lineage (genotypes #1 and #2), 3 belong to genotype #3 and 1 belongs to genotype #4. Genotype #1 and #2 have Type II alleles at all genetic loci except the former has Type II allele and the latter has a Type I allele at locus Apico. Both genotype #1 and #2 are considered to belong to the clonal Type II lineages. Genotype #3 and #4 are non-clonal isolates. Results indicate low genetic diversity among T. gondii isolates from pigs in the U.S.