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Hair Worms (Trichostrongylus axei)

Scientific name: Trichostrongylus axei Common name: Hair worms Physical description of parasite: The adult worm is tiny (0.5 cm long) and hair-like. Stages/lifecycles: The adult worm occurs in the stomach and in the small intestine, irritating and eroding the finger-like projections, or villi, of the gut, damaging the capillaries and lymph vessels within the villi. How the parasite enters the horse's system: The horse eats grasses infected with eggs of the stomach hair worm. The eggs hatch and the larvae move into the stomach where they mature and lay more eggs which are passed in the manure. Effects of parasite if left untreated: When a horse is infected with hair worms, he is usually also infected with other worms. Damage caused by the hair worm can be worsened by other worms in the system. Signs of infection may be dark, foul-smelling diarrhea, because the damaged villi are unable to digest and absorb properly in the intestine. If there is severe damage to the villi, the underlying small vessels could be damaged as well, causing bleeding into the intestines. Bleeding may lead to anemia and loss of condition. Foals are very open to infection by hair worms, so broodmares should be dewormed and moved to clean pastures.