In collaboration with the annual herd control efforts throughout Minnesota and Iowa, researchers examined 88 pregnant white-tailed deer and their fetuses for evidence of Toxoplasma gondii infection. Fifty-eight (66%) were seropositive according to the modified agglutination test. Parasites were isolated from the fetuses of 15 deer, 5 of which were seronegative. Each of the 15 isolates was sequenced for genotyping, and 13 were identified as clonal or recombined type II strains. Interestingly, type II is by far the most prevalent strain infecting humans in the United States, with some reports as high as 80%.

Toxoplasma is known to be widespread in wildlife populations throughout the United States; prevalence in deer reported previously ranged from 30% to 60%. In retail meat, however, a recent nationwide study found the parasite in less than 1% of more than 6200 samples. White-tailed deer are one of the most popular game animals, with tens of millions of animals hunted in the United States each year. The high numbers of potential reservoir hosts combined with the genotyping data reported in this paper clearly point to undercooked venison as a likely source of toxoplasmosis.

Transplacental toxoplasmosis in naturally infected white-tailed deer: Isolation and genetic characterization of Toxoplasma gondii from foetuses of different gestational ages. Dubey JP, Velmurugan GV, Ulrich V, et al. INTL J PARASITOL 38:1057-1063, 2008.