Baylisacaris is a parasitic disease caused by a roundworm (Baylisascaris procyonis). Infection is caused when the eggs of the parasite are ingested or meat from an infected animal is eaten. Raccoons are the natural definitive host for the parasite and do not experience disease from it. However, unlike many parasites, Baylisascaris can infect a number of intermediate host species and is known to infect at least fifty types of animals. However, each sub-species is most comfortable in a particular host and will affect a foreign animal differently.