Occurrence, isolation, and genetic characterization of Toxoplasma gondii from white-tailed deer (Odocoileus virginianus) in New Jersey.

The ingestion of uncooked infected white-tailed deer (WTD) tissues can transmit Toxoplasma gondii infection to humans and mesocarnivores, including cats. In the present study, we tested 264 WTD from New Jersey for T. gondii infection during the 2011-2012 hunting season. Serum samples were tested for antibodies to T. gondii by the modified agglutination test (cutoff titer, 25); 76 (28.7%) of 264 WTD were seropositive. Heart muscle samples from 64 seropositive WTD were digested in pepsin, and the digests were bioassayed for the isolation of T. gondii . Viable T. gondii was isolated in mice from the myocardium of 9 WTD; tachyzoites from infected mouse tissues were further propagated in cell culture. One of the 9 strains was highly virulent for outbred Swiss Webster mice. The DNA isolated from culture-derived tachyzoites of these 9 T. gondii isolates 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). Six genotypes were found, including ToxoDB genotype no. 2 (Type III), no. 3 (Type II variant), no. 4 (Type 12), no. 216, no. 220, and no. 221. The last 2 were new genotypes that were reported for the first time. This is the first report of T. gondii infection in deer from this region of the United States.

Isolation and genetic characterization of Toxoplasma gondii from mute swan (Cygnus olor) from the USA.

Little is known of the genetic diversity of Toxoplasma gondii circulating in wildlife. In the present study, antibodies to T. gondii were determined in serum samples from 632 mute swans (Cygnus olor) collected from different areas of the USA. Sera were tested by T. gondii modified agglutination test; 54 (8.5%) of 632 samples were seropositive with titers of 25 in 28 sera, 50 in 22 sera, 100 in three samples, and 200 or higher in one swan. Hearts from 14 seropositive swans were bioassayed in mice and viable T. gondii (designated TgSwanUs1-3) were isolated from the hearts of three. These three T. gondii isolates 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 of genotyping revealed that two strains (TgSwanUs1, TgSwanUs2) were Type III (ToxoDB PCR-RFLP genotype #2), and TgSwanUs3 was a new genotype designated here as ToxoDB PCR-RFLP genotype #216. Pathogenicity of oocysts derived from these three strains was determined in Swiss Webster (SW) outbred mice. All mice infected with oocysts and tachyzoites of the atypical isolate (TgSwanUs3) died of acute toxoplasmosis, irrespective of the dose. Oocysts of the remaining two isolates were less pathogenic but differed from each other; 10 oocysts of the TgSwanUs1 killed all inoculated mice whereas 1 million oocysts of the TgSwanUs2 were needed to kill all infected SW mice. Isolation of T. gondii from mute swan indicates that the local waters were contaminated by T. gondii oocysts, and that mouse T. gondii virulent strains are circulating in wildlife. Mute swan is a new host record for T. gondii.