Intestinal Threadworms (Strongyloides westeri)

Scientific name: Strongyloides westeri Common name: Intestinal Threadworms Physical description of parasite: Threadworms are long and hair like. Adults grow to be 8 to 9 mm in length (about 2/5 inch). Stages/lifecycles: Larvae mature to adult worms in the small intestine. Infection can occur by eating infective larvae or by penetration through the skin. If the larvae enter the horse's system through its skin, they move to the lungs, then up the wind pipe where they are coughed up and swallowed. They mature in the small intestine, where adult females lay the eggs that are passed out in the manure. How the parasite enters the horse's system: The infective larvae of the threadworm can either be swallowed by the horse or the larvae can go through the horse's skin. Young foals can also be exposed to the worm by nursing from their infected mothers. Effects of parasite if left untreated: If the larvae enter through the skin the next stop is the lungs, where they can cause bleeding and respiratory problems. Inflammation and rashes can develop where the larvae penetrated the skin. The worst damage occurs in untreated foals. Infected through their mothers' milk, they can suffer diarrhea, weakness, weight loss and failure to thrive and grow at a normal rate. Veterinarians generally recommend deworming your foal early in life and as often as every month until weaning. Diarrhea in 7-10 day old foals may be caused by intestinal threadworms. Deworming may be beneficial in these cases. Be very careful to read your dewormer's label - some products cannot be used on foals this young.