Equine Parasites

Equine Parasites

What you can’t see, can and will hurt your horse. Your horse may look fat and healthy, but remember that your horse does not have to look “wormy” to be infected with parasites.  In fact, most of the damage done by equine parasites is sub clinical.  As parasites grow in your horse’s system, they will start to rob your horse of vital nutrients and eventually cause extensive damage to intestines, arteries, liver and lungs.  This will start to affect how your horse feels and performs.  Sometimes parasites can be the cause for colic’s in horses and respiratory disease in foals.  Even though you can’t see it, the damage is internal and very real. Listed below are some internal parasites that can affect horses.


Large Strongyles Large strongyles, otherwise known as bloodworms, are parasites known to be the most destructive and deadly of all equine parasites.  As immature larvae migrate through the horse’s blood vessels, they begin to destroy arterial walls, block or rupture blood vessels, damage circulation, organs and tissues.  This parasite can result in your horse getting anemia, fever, lethargy, diarrhea and sometimes colic.

Small Strongyles This parasite lives and migrates within the intestinal tract.  If left undetected will cause inflammation of the intestines, anorexia, diarrhea, weight loss and possibly colic.

Ascarids  (Roundworms) The medical term is Ascarids but the more commonly known name is “roundworms”.  This type of parasite most often affects the young horses, such as yearlings, weanlings and sucklings.  Roundworms can cause damage to the horse’s liver and lung tissue.  Some signs to watch for are fever, coughing, and pneumonia.  Roundworms that reach the adult stages will live in the small intestine, which becomes even more serius, if left untreated it can cause colic.

Bots This parasite is actually considered to be an internal parasite, yet they live outside the body.  In the larvae stage the parasite lives in the horse’s mouth or stomach, when it reaches maturity it will move to the outside of the horse creating more larvae for the horse to ingest.  Bots will cause mouth sores and more serious problems like stomach ulcers.

Pinworms  If you notice your horse itching and scratching around the tail area, you might want to check your horse for pinworms.  Pinworms will live and multiply in your horse’s rectum.

All of the equine parasites mentioned above are very uncomfortable and most importantly can be harmful to your horse.  Village Veterinary Hospital strongly suggest that you worm your horse’s and we will be glad to discuss with you a worming schedule that is best for your horse.  Please contact our office at 505-869-2627 and one of our doctor’s will be glad to assist you.