White-Tailed Deer & Coccidia

Coccidia, such as Neospora caninum and Toxoplasma gondii, infect both humans and domestic animals. Although both usually cause subclinical infection in adults, transplacental transmission can lead to abortion or severe birth defects. It has been known for years that white-tailed deer (WTD) are important reservoir hosts for several coccidian parasites in the United States. This study sought to define a more accurate seroprevalence of N caninum and T gondii in WTD by the use of 4 serologic testing methods. Of 232 WTD from Minnesota and Iowa, 111 (48%) were positive for T gondii and 194 (84%) were positive for N caninum by any one of the tests. Forty-seven deer (20%) had antibodies to both parasites. More than half of the seropositive WTD had positive results on all 4 tests, and some animals had antibody titers as high as 1:3200.

COMMENTARY: The results of this study underline the importance of WTD as reservoir hosts for coccidian parasites. As overpopulation and habitat loss force wildlife populations closer to residential areas, many parasites benefit from enhanced transmission between hosts. Wildlife killed by auto accidents or by hunters can become a source of infection for dogs and humans through infective cysts in the meat. As always, venison should be cooked thoroughly and raw scraps tossed into the trash instead of the dog bowl.—Carly Jordan, PhD candidate (parasitology/cellular biology)

Seroprevalence of Neospora caninum and Toxoplasma gondii antibodies in white-tailed deer (Odocoileus virginianus) from Iowa and Minnesota using four serologic tests. Dubey JP, Jenkins MC, Kwok OC, et al. VET PARASITOL 161:330-334, 2009.