When ingested, the larva migrate and reach lengths of 1.5 to 2.0 mm. The eggs hatch, and the larvae migrate to the brain, eyes and other organs. The parasite has been implicated in cases of serious eye disease or central nervous system disorders and infection can cause death or paralysis depending on the location in the body and number of worms. Human infection with the toxiocaris larvae of canine or feline roundworms is known collectively as toxocariasis. All cases of toxocariasis come from pets, according to the Texas Dept. of Health, Div. of Zoonosis Control, which states an estimated 10,000 new cases of roundworm infection occur in children every year, most often as a result of eating dirt contaminated with animal feces.
Most human infections are mild enough to go unnoticed and apparently produce no permanent damage.
However sometimes infection results in severe and even fatal disease. Common symptoms include abdominal pain, headache, weakness, lethargy and wheezing. Due to the public health significance, it is important to distinguish Baylisascaris from Toxocara. Over 177 local wild raccoons were systematically executed before a lawsuit by the City's concerned citizens brought the killings to a halt. Eradication of raccoons will not prevent the very rare disease visceral larva migrans in humans.