Submitted to: International Journal for Parasitology
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/21/2011
Publication Date: 8/1/2011
Citation: Dubey, J.P., Velmurugan, G., Rajendran, C., Yabsley, M., Thomas, N.J., Beckman, K.B., Sinnett, D., Ruid, D., Paul, W., Hart, J., Fair, P.A., Mcfee, W.E., Shearn-Bochsler, V., Kwok, O.C., Ferreira, L., Choudhary, S., Faria, E.B., Zhou, H., Felix, T.A., Su, C. 2011. Genetic characterization of Toxoplasma gondii in wildlife from North America revealed widespread and high prevalence of the fourth clonal type. International Journal for Parasitology. 41:1139-1147. 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. Why some people become sick whereas others do not is not clear. In the present study scientists document genetic diversity of Toxoplasma in wildlife.The results will be of interest to biologists, parasitologists, and public health workers.
Technical Abstract: Little is known of the genetic diversity of Toxoplasma gondii circulating in wildlife. In the present study, wild animals, including dolphins from the USA were examined for T. gondii infection. Tissues of naturally exposed animals were bioassayed in mice for isolation of viable parasites. Viable T. gondii was isolated from 30 animals, including for the first time from a bald eagle (Haliaeetus leucocephalus), one barn owl (Tyto alba), five wolves (Canis lupus), a woodrat (Neotoma micropus), and five arctic foxes (Alopex argopus). Additionally, 65 T. gondii isolates obtained previously, but not genetically characterized, were revived in mice. Toxoplasma gondii DNA isolated from these 95 samples (30+ 65) was characterized using 10 PCR-RFLP markers (SAG1, 5’- and 3’-SAG2, alt.SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, a new SAG2 and Apico). A total of 93 isolates were successfully genotyped. In addition to clonal Types II, and III, 12 different genotypes were found. These genotype data were combined with 74 T. gondii isolates previously characterized from wildlife from North America and the composite data set of 167 isolates included 22 genotypes, including clonal Types II, and III and 20 atypical genotypes. Phylogenetic network analysis showed that the Type II and three atypical genotypes formed a distinct cluster. This cluster and the clonal Type III together accounted for 85.6% strains in North America. One of the genotypes in the Type II cluster includes previously identified Type A and X strains from sea otters, and this genotype is dominant in wildlife of North America. No clonal Type I strain was identified from these wildlife isolates. These results suggest that T. gondii strains in wildlife from North America have limited diversity with occurence of a few dominant clonal types.