Common Parasites in the Horse

Protecting your horse against parasites is part of good barn management. Whether you are the owner of single horse or make your living as a boarding stable, you should have a good parasite prevention plan in place. Deworming your horses at regular intervals will keep parasites at bay and will ensure your horse's maximum health and safety.

What are some of the more common nasties just itching to sponge off your equine friends? Check out these parasite profiles.

• Large Strongyles (Strongylus vulgaris and Strongylus edentatus). Otherwise known as bloodworms, large strongyles are an internal parasite known to be the most destructive and deadly of them all. Why are they so destructive? Well, as immature larvae migrate through the blood vessels, they destroy arterial walls, block or rupture blood vessels, impair circulation, and damage organ and tissues. Not exactly the most polite of guests, are they? Seriously, large strongyles are no joke! The havoc they wreak can result in colic, anemia, diarrhea, fever, lethargy, depression, and loss of appetite. How to prevent large strongyles from getting the best of your horse? Use a dewormer that treats both adult worms and the more destructive arterial larvae. Ask your veterinarian for a recommendation, as many dewormers treat only the less dangerous adult worms.

• Small strongyles. Small stronglyles live and migrate within the intestinal tract. While they don't travel any further than this, they too can pack quite a punch. Small strongyles, if left undetected, can cause inflammation of the intestines, anorexia, weight loss, diarrhea, and colic. A good dewormer is your best defense.

• Ascarids (Parascaris equorum). Ascarids are also known by their more common name of roundworm. While ascarids are very dangerous parasites, they most often affect very young horse such as sucklings, weanlings, and yearlings. Ascarids in the migrating larval stages can damage a horse's lung and liver tissue. Some of the signs include lethargy, coughing, fever, pneumonia, and other infections and issues affecting the respiratory tract. Ascarids who reach the adult stage hang out in the small intestine, where they can cause problems like colic, ruptured gut, blockage, and death. They are dangerous nasties indeed, but can be easily prevented with a parasite protection program.

• Bots (Gastrophilus). How's this for weird? Bots are considered an internal parasite, and yet they live on the outside of a horse's body. Say what? Well, here's how it works. In its larval stage, the botfly lives in the horse's stomach and mouth. As it reaches maturity the bot leaves the internal environment and hangs out on the outside of the horse, where it creates more larvae to be ingested by the horse. At the very least, bots cause inflammation and sores in the mouth. They can also cause more serious problems like stomach irritation and ulceration and perforation of the stomach wall. In extreme cases, bots can block stomach outflow into the small intestine, causing colic and possibly death. Effectively ridding your horse's of bots requires a two-pronged approach. First, you'll need to treat the outside of your horses by removing bots with a special comb. Then you'll have to follow up by administering a dewormer.

• Pinworms. (Oxyuris equi). If your horse seems uncomfortable around the tail region-say there's a lot of itching and scratching going on-suspect pinworms. Pinworms live and mate in the horse's rectum, and cause such unpleasant issues as tail rubbing. Again, the right dewormer is all it takes to rid your horse of pinworms.

• Intestinal threadworms (Stronyloides westeri) Threadworms usually affect young horses. If your foal has diarrhea, lack of appetite, is losing weight or is not growing what you think is the right amount of hair, consider threadworms as a possible culprit. Since many dewormers don't effective treat threadworms, talk to your vet about a good course of action.

• Summer sores (Habronema and Draschia) If a fly deposits larvae in the open skin or a wound on the horse's body, the result is often summer sores. The larvae can cause conjunctivitis, nodules in the stomach wall, and gastritis.

Remember, there's no room at the inn for parasites! With good barn management, you can ensure that your horses remain parasite free.