Location: Animal Parasitic Diseases LaboratoryTitle: Isolation and characterization of new genetic types of toxoplasma gondii and prevalence of trichinella murrelli from black bear (Ursus americanus)) Author
Submitted to: Veterinary Parasitology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/13/2013
Publication Date: 8/1/2013
Publication URL: http://handle.nal.usda.gov/10113/57118
Citation: Dubey, J.P., Hill, D.E., Zarlenga, D.S., Choudhary, S., Ferreira, L., Oliveira, S., Verna, S., Kwok, O.C., Driscoll, C., Spiker, H., Su, C. 2013. Isolation and characterization of new genetic types of toxoplasma gondii and prevalence of trichinella murrelli from black bear (Ursus americanus). Veterinary Parasitology. 196:24-30. 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 under cooked meat from infected animals and food and water contaminated with oocysts. Trichinella species are worms that can also cause serious illness in humans who ingest infected uncooked meat, especially game. In the present study scientists found Toxoplasma and Trichinella infections in bears that were hunted. The results will be of interest to biologists, parasitologists, and public health workers. Bear meat should be cooked well before consumption.
Technical Abstract: Black bears (Ursus americanus) are hosts for two important zoonotic parasites, Toxoplasma gondii and Trichinella spp. and bears are hunted for human consumption in the USA. Little is known of the genetic diversity of T. gondii circulating in wildlife. In the present study, antibodies to T. gondii were found in juice from tongues of 17 (25.7%) of 66 wild black bear from Maryland during the hunting season of 2010 and 2011. Antibodies to T. gondii were assessed by the modified agglutination test. Tongues of 17 seropositive bears were bioassayed in mice and viable T. gondii was isolated from three samples. These three T. gondii isolates (TgBbMd1-3) were further propagated in cell culture and DNA isolated from culture-derived tachyzoites was characterized using 11 PCR-RFLP markers (SAG1, 5’- and 3’-SAG2, alt.SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1 and Apico). Results revealed three genotypes. TgBbMd1 is a Type 12 strain (ToxoDB PCR-RFLP genotype #4) and TgBbMd2 is a new genotype, designated as ToxoDB PCR-RFLP genotype #216, and TgBbMd3 is a Type II clonal strain (ToxoDB PCR-RFLP genotype #1).The isolate TgBbMd2 was highly virulent for outbred Swiss Webster mice. Results indicate that mouse virulent strains of T. gondii are circulating in wildlife in the USA. These 66 tongues in addition to tongues collected during hunts in previous years were further investigated for the presence of muscle larvae of Trichinella spp. Tongues from 40 bears in 2005, 41 in 2006, 51 in 2007, 56 in 2008, 68 in 2009, 67 in 2010, and 66 in 2011 were subjected to digestion with pepsin/HCl and microscopic examination. Two bears were infected with Trichinella spp.; one in 2008 and one in 2009. Genotyping of collected muscle larvae revealed that the infecting species in both cases was Trichinella murrelli.