The parasite is transmitted when the eggs are ingested by another animal. Humans generally become infected from accidentally ingesting eggs from soil, water, hands, or other objects which are contaminated with raccoon feces. The severity of the disease depends to a large extent on how many eggs are ingested. These eggs hatch into larvae which then cause disease by migrating through the central nervous system, eyes, and other organs. Symptoms include nausea, lethargy, liver enlargement, incoordination, loss of muscle control, coma, and blindness.
Fatalities are rare, but have been reported.
There have been no human cases reported in Wisconsin. In general, symptoms appear one to three weeks post-infection, although they may take as long as two months. This interval depends on the number of eggs ingested. Because of young children's tendency to put their fingers or objects into their mouths, they are at risk if they play in areas which are frequented by raccoons. Hunters, trappers, taxidermists, and wildlife rehabilitators are also at increased risk if they handle raccoons or items contaminated with raccoon feces.