Toxocara canis is the predominant cause of a serious condition called "Visceral Larva Migrans" in humans. Most victims are children. They are infected by inadvertantly consuming worm eggs in soil (typically by getting dirty fingers in their mouths). The worm is not present in its correct host but tries to complete its life cycle anyway. The worm gets lost in the human body (classically in the eye), dies, and generates an extreme inflammatory reaction. If the worm dies within the human eye, blindness usually results.

For this reason, it is important for parents to be aware of this hazard. Proper hand-washing will prevent infection. Monthly pet deworming will reduce environmental contamination. Public leash laws and restriction of dog walking are meant to reduce fecal contamination of public areas. Stray cats should be kept away from children's sandboxes.

For more information on this subject, please visit one of the Center for Disease Control Web sites on Visceral Larva Migrans at: Ascarid Prevention
(how to prevent transmission of intestinal roundworms from pets to people)