Baylisascaris procyonis is a type of roundworm found in raccoons. This roundworm can also infect humans and other animal species, including dogs. For people, infections are rare, with fewer than 25 cases documented in the United States. Symptoms from infection with this roundworm can be severe if the roundworm invades the eye (ocular larva migrans), organs (visceral larva migrans), or the brain (neural larva migrans). Eggs from the roundworm are passed in raccoon feces and become infective after being in the environment for 2-4 weeks. Because of this, anyone having contact with areas where raccoons frequent may be at risk for exposure to Baylisascaris.
There is limited surveillance data available on Baylisascaris. Human cases have been reported in California, Illinois, Louisiana, Massachusetts, Michigan, Minnesota, Missouri, New York, Oregon, and Pennsylvania. As of 2012, there were 16 published human neurological cases in the US; six of the infected persons died.