Parasites in Horses: Managing Common ‘Worms’

Learn about the lifecycles of common found parasites in horses and how to manage them.

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Parasites in horses
The results from the FEC will help your veterinarian determine what kind of dewormer should be administered, if your horse needs one at all. | Photo: iStock

By Kristen Stowell, DVM

Parasites in horses can result in numerous equine health issues. Infected horses can exhibit:

  • Weight loss;
  • Diarrhea;
  • Colic;
  • And unthrifty coat;
  • Skin sores;
  • Suboptimal performance; and
  • The dreaded itchy bum.

Here, we’ll detail the lifecycle of commonly found parasites in horses in Illinois and how to manage them.

The Parasites

Large Strongyles These are the most dangerous but least common parasites in horses. Horses acquire large strongyles by grazing pasture covered with worm larvae. They ingest the grass and, inadvertently, the immature worms. The larvae travel through the horse’s gastrointestinal system and can invade the cecum and colon’s blood vessels, where they compromise gut function and vitality. Large strongyles aren’t as common now as they previously were. Nonetheless it’s critical to stick to an appropriate deworming program. Signs of infection include weight loss, diarrhea, and colic

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