ABSTRACT Toxoplasmosis in wild turkeys ( Meleagris gallopavo ) is of epidemiological interest because turkeys feed from the ground, and detection of infection in turkeys indicates contamination by oocysts in the environment. During the 2018 spring hunting season in Pennsylvania, fresh (unfixed, not frozen) samples were obtained from 20 harvested wild turkeys and tested for Toxoplasma gondii infection. Hearts from all wild turkeys and skeletal muscle from 1 were bioassayed for T. gondii by inoculation in outbred Swiss Webster (SW) and interferon-gamma gene knockout (KO) mice. Antibodies to T. gondii were detected in 1:5 dilution of neat serum from 5 of 15 wild turkeys and in fluid from the heart of 1 of 4 wild turkeys with the modified agglutination test (MAT); neat serum was not available from 4 wild turkeys. Viable T. gondii was isolated from hearts of 5 wild turkeys, 1 with MAT of 1:10, 1 with MAT of 1:5, and 3 seronegative (MAT < 1:5). Toxoplasma gondii was isolated from both heart and skeletal muscle in the 1 wild turkey that had skeletal muscle submitted. The KO mice inoculated with tissue from all 5 infected wild turkeys died or were euthanatized when ill, 7–21 days post-inoculation (PI). Tachyzoites were detected in lungs of all KO mice, and the T. gondii strains were successfully propagated in cell culture. The SW mice inoculated with tissues of wild turkeys remained asymptomatic, and tissue cysts were seen in the brains of infected mice when euthanatized in good health at 46 days PI; 1 of the 2 SW mice inoculated with the heart of 1 turkey died on day 26, and tachyzoites were detected in its lung. Genetic typing on DNA extracted from culture-derived tachyzoites using the PCR restriction fragment length polymorphism with 10 genetic markers (SAG1, SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico) revealed that 4 isolates belonged to ToxoDB PCR-RFLP genotype #5 and 1 was genotype #216.

Rodents are known to be reservoir hosts of Toxoplasma gondii infection for other animals, such as cats and pigs. From February to July 2017, 167 rats ( Rattus norvegicus ) were trapped in Grenada, and serum, heart, skeletal muscle, and brain were examined for T. gondii infection by serological examination (modified agglutination test, 1:25) for T. gondii antibodies and for viable parasites by bioassay in mice. Samples of heart, skeletal muscle, and brain of all rats were bioassayed in Swiss Webster (SW) outbred albino mice and interferon gamma gene knockout (KO) mice. Toxoplasma gondii was isolated from heart and brain from 1 rat; this was the only seropositive rat. The T. gondii strain was avirulent for SW mice but killed KO mice. Tissue cysts were detected in the brains of SW mice, and tachyzoites were detected in the lungs of KO mice that died of acute toxoplasmosis. The strain was propagated in cell culture, and DNA derived from cell-cultured tachyzoites was genotyped using the 10 PCR restriction fragment length polymorphisms (SAG1, SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and Apico). The strain was a clonal Type III (ToxoDB genotype no. 2) strain. Although the prevalence of T. gondii in humans and animals in Grenada is high, rats seem to have little importance in the transmission of T. gondii on this island.