The sylvatic cycle of Neospora caninum: where do we go from here?

Bovine abortions due to Neospora caninum infection are a major cattle-production problem worldwide. The parasite is readily maintained in cattle populations by vertical transmission. The domestic dog excretes oocysts in its feces and, after sporulation, these oocysts are infectious to cattle. Current control measures are aimed at culling infected cows and limiting the access of cattle to infective oocysts. The recent revelations that coyotes (Canis latrans) can excrete N. caninum oocysts in their feces and that white-tailed deer (Odocoileus virginianus) are natural intermediate hosts of the parasite demonstrate the existence of a sylvatic cycle of neosporosis in North America. This complicates parasite-prevention programs but opens many new and exciting avenues of research. Similar canid-ruminant sylvatic cycles might exist in other countries and, if so, need to be investigated.