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Title: Isolation and genetic characterization of Toxoplasma gondii from black bears (Ursus americanus), bobcats (Felis rufus), and feral cats (Felis catus) from Pennsylvania

item Dubey, Jitender
item VERMA, SHIV - Non ARS Employee
item CASSINELLI, ANNA - Non ARS Employee
item Kwok, Oliver
item VAN WHY, KYLE - Animal And Plant Health Inspection Services (APHIS), National Wildlife Center
item SU, CHUNLEI - University Of Tennessee
item HUMPHREYS, JAN - Indiana University Of Pennsylvania

Submitted to: Journal of Eukaryotic Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/31/2014
Publication Date: 11/1/2014
Citation: Dubey, J.P., Verma, S., Calero-Bernal, R., Cassinelli, A., Kwok, O.C., Van Why, K., Su, C., Humphreys, J. 2014. Isolation and genetic characterization of Toxoplasma gondii from black bears (Ursus americanus), bobcats (Felis rufus), and feral cats (Felis catus) from Pennsylvania. Journal of Eukaryotic Microbiology. DOI: 10.1111/jeu.12196.

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. Detection of the oocyst (cat feces contamination) is a problem because of the low concentration of oocysts in the watershed/reservoirs. In the present study, authors used prevalence of T. gondii in black bears as sentinels for testing environmental contamination in the wild. They detected T. gondii antibodies in 32 (84.2%) of 38 bears, both bobcats, and 2 of 3 feral cats. Over 2 decades the prevalence of Toxoplasma in bears in Pennsylvania has remained stable at 80%. Additionally, bear are one of the game animals. Our results indicate that highly virulent strains of T. gondii are circulating in animals that are part of human food chain. The results will be of interest to biologists, and parasitologists.

Technical Abstract: Toxoplasma gondii infects virtually all warm-blooded hosts worldwide. Recently, attention has been focused on the genetic diversity of the parasite to explain its pathogenicity in different hosts. It has been hypothesized that interaction between feral and domestic cycles of T. gondii may increase unusual genotypes in domestic cats and facilitate transmission of potentially more pathogenic genotypes to humans, domestic animals, and wildlife. In the present study, we tested black bear (Ursus americanus), bobcat (Felis rufus), and feral cat (Felis catus) from the state of Pennsylvania for T. gondii infection. Antibodies to T. gondii were found in 32 (84.2%) of 38 bears, both bobcats, and 2 of 3 feral cats tested by the modified agglutination test (cut off titer 1:25). Hearts from seropositive animals were bioassayed in mice, and viable T. gondii was isolated from 3 of 32 bears, 2 of 2 bobcats, and 2 of 3 feral cats. DNA isolated from culture-derived tachyzoites of these isolates was characterized using multilocus PCR-RFLP markers. Three genotypes were revealed, including ToxoDB PCR-RFLP genotype #1 or #3 (Type II, 1 isolate), #5 (Type 12, 3 isolates), and #216 (3 isolates), adding to the evidence of genetic diversity of T. gondii in wildlife in Pennsylvania. Pathogenicity of 3 T. gondii isolates (all #216, 1 from bear, and 2 from feral cat) was determined in outbred Swiss Webster mice; all three were virulent causing 100% mortality. Results indicated that highly mouse pathogenic strains of T. gondii are circulating in wildlife, and these strains may pose risk to infect human through consuming of game meat.