The toxocara parasite is a roundworm that lives in the intestines of cats and dogs, particularly stray animals. The microscopic eggs are shed in the animals’ feces, contaminating yards, playgrounds and sandboxes. Toxocara can infect the intestine, liver, lungs, eyes, and brain, of humans; and scattered scientific articles reported toxocara in the central nervous system. Toxocara has been linked to lower intelligence and epilepsy, developmental delays, and damage to learning and cognition. Children who tested positive for toxocara had lower mean test scores, and the greater the magnitude of the toxocara infection the greater the impairment. It has been estimated approximately sixteen million people carry antibodies to toxocara, indicating current and chronic parasitic disease, yet doctors seldom consider the diagnosis. The long-term implications of the failure to diagnose toxocara are significant.