Surveillance for Baylisascaris procyonis in raccoons (Procyon lotor) from Wyoming, USA.

Baylisascaris procyonis is a common roundworm of raccoons that causes severe clinical disease in many vertebrates, including humans. The distribution of B. procyonis in the US is poorly documented in portions of its range and has not been reported from Wyoming. Our objectives were to determine the statewide distribution and prevalence of this parasite in raccoons in Wyoming, using intestinal and fecal examinations. We examined 363 raccoons from 23 Wyoming counties in 2009-11, testing the reliability of two methods (intestinal extrusion and incision) to determine worm burdens. We found 163 raccoons (45%) positive for B. procyonis. The two methods of examination did not differ, although extrusion missed some infections. Neither age nor sex affected apparent prevalence or worm burdens. Prevalence did not differ with land use, yet burden was highest among rural raccoons. Fecal examination revealed that juvenile raccoons had a higher proportion of patent infections than adults, but neither sex nor location were indicators of prevalence. Egg density (eggs per gram of feces) did not differ by sex or age; however, rural raccoons had higher egg densities than urban/suburban animals. Understanding the distribution and prevalence of B. procyonis in Wyoming, especially in and around highly populated areas, is an important step in educating the general public and medical community on the potential risks of raccoon roundworm infection.