Encysted Small StrongylesMore Info›
Adult small strongyles live in the large intestine, producing eggs expelled in feces. All 3 major deworming compounds kill adults. However, the worst family members are the encysted larvae that burrow into intestinal walls and contribute to poor condition. The abrupt, large emergence of larvae from the walls can cause a potentially fatal case of colic or severe diarrhea. Only two drugs can kill encysted small strongyles: a five-day larvicidal dose of fenbendazole (Safe-Guard® Power-Dose® or Panacur® Powerpac®) or moxidectin.
Roundworms, or ascarid larvae, migrate through intestinal walls to the liver and then to the lungs, often causing severe damage to both respiratory and digestive systems. Foals and young horses under age 2 are the most vulnerable. Foals should be treated with a double-dose of fenbendazole at 8 to 12 weeks of age, as roundworms have become less susceptible to some, or all, of the other major compounds in some regions or on certain farms.
Eggs are laid around the anus of an infected horse. Horses will rub the tail and rectal area to relieve itching caused by the adhesive nature of the deposited eggs, resulting in hair loss and raw skin patches. It affects all ages, and any of the 3 major deworming compounds will kill pinworms.
Also called bloodworms, large strongyle larvae weaken abdominal artery walls causing symptoms that range from diarrhea and weight loss to potentially fatal colic due to obstruction of blood flow. While all compounds are effective against adults, if no resistance, only macrocyclic lactones and larvicidal dosages of fenbendazole are effective against larvae. Young horses are most vulnerable.