Baylisascaris infection is caused by a roundworm found in raccoons. This roundworm can infect people as well as a variety of other animals, including dogs. Human infections are rare, but can be severe if the parasites invade the eye (ocular larva migrans), organs (visceral larva migrans) or the brain (neural larva migrans).
Image: Left: Embryonated B. procyonis egg, showing the developing larva inside. Right: Larva of B. procyonis hatching from an egg. Center: Raccoons are hosts for the roundworms that can cause Baylisascaris infection. Credit: DPDx, U.S. Fish & Wildlife Service