The relationship between zoonosis caused by a common roundworm in dogs, Toxocara canis, and allergic asthma in children living in urban settings is being studied. Visceral larva migrans (VLM) develops when humans ingest the eggs of the canine ascarid Toxocara canis normally shed in the feces of infected dogs. Once ingested, the eggs hatch to release larvae which eventually die and trigger a strong host eosinophilic inflammatory response. Living conditions in poor communities render children especially vulnerable to T. canis infection.