Infection in humans of dog, cat, or fox roundworm. Major cause of blindness, and may provoke rheumatic, neurologic, or asthmatic symptoms,Encyclopedia Entry for Toxocariasis :Toxocariasis (Ocular Larva Migrans (OLM)). Source of disease: Toxocara canis or Toxocara catiEncyclopedia Entry for Toxocariasis :Toxocariasis (Visceral Larva Migrans (VLM)). Source of disease: Toxocara canis or Toxocara cati