Toxocara canis, the canine roundworm, 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). In this situation, 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, permanent partial 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 where Toxocara felis eggs can contaminate the play area.
Keep in mind that fresh feces does not contain infectious Toxocara eggs;
the eggs must mature 30 days or so in the environment to become infectious.
This means that the fecal matter is unlikely to be evident;
the problem is contaminated dirt.
For more information on this subject, please visit one of the Center for Disease Control Web sites on Visceral Larva Migrans at:
(for a fact sheet on Toxocariasis)
(how to prevent transmission of intestinal roundworms from pets to people)
Page last updated: 1/22/11