The common roundworm found in dogs is a rare but potentially serious cause of human disease. The larval stages of this worm burrow through the gut wall and become embedded somewhere within the body and can cause serious damage if they end up, for example, in the eye. There are occasional reports of the victim, usually a child, being blinded in one eye. However, the type of roundworm normally found in cats is much less likely to cause problems in humans and most of the parasites found in cats are unable to survive at all in people.