Ascarids or Roundworms (Parascaris equorum)

Lifecycle: Eggs are passed in manure and become infective larvae in the grass. While grazing, the horse swallows the larvae, which hatch and burrow into the walls of the intestine. From there, they are carried by the bloodstream into the liver and lungs. The horse coughs up the larvae and swallows them again. Larvae mature into egg-laying adults in the intestine.


How It Gets Into Your Horse: Ascarid larvae are swallowed as your horse eats infected grass.

Dangers If Left Untreated: Ascarids are especially dangerous to foals aged 6 months or younger. Severe infection in horses this young can build up quickly and lead to liver and lung damage, poor growth and even death. Larvae in the bloodstream can cause coughing, fever, pneumonia, bleeding lungs and respiratory infections. In the adult stage, ascarids live in the small intestine where they can cause colic, blockage, ruptured gut and death.