Description
Strongyloides westeri is a parasite that usually infects nursing foals. When a foal nurses from an infected mare, parasite larvae are passed from mother to foal through the milk. In about two weeks the larvae mature and produce eggs that the foal passes in its feces, sometimes as diarrhea. The larvae may also infect the foal by crossing the placenta. Foals usually become resistant to the disease by four months of age. While some grown horses maintain a low-level infection, they rarely manifest any symptoms. Some adult horses become infected after the infective larvae penetrate their skin or oral mucous membranes such as the gums.