Horses are susceptible to numerous parasite species, which can pose significant health risks and affect their overall well-being, performance, and quality of life. Proactive parasite prevention is critical to safeguard your horse, and our Rustebakke Veterinary Service team explains all you need to know about equine parasites. 

Strongyles in horses

Strongyles, commonly known as bloodworms, are among the most prevalent and dangerous internal parasites that affect horses. They are categorized as large and small strongyles, and each poses significant health risks:

  • Large strongyles — Large strongyle larvae are ingested from contaminated pasture, migrate through the intestinal wall, and travel via the bloodstream to the blood vessels that supply the intestine, liver, spleen, and pancreas. They can cause significant damage to these blood vessels, potentially leading to thromboembolic colic, a possibly life-threatening condition. Signs include weight loss, anemia, and colic.
  • Small strongyles — Small strongyles encyst in the intestinal walls and can remain dormant for extended periods. When they emerge, they can cause damage to the intestinal lining. Signs include diarrhea, weight loss, colic, and poor coat condition.

Roundworms in horses

Roundworms most commonly affect foals and young horses. Horses become infected by ingesting eggs from contaminated feed, water, or surfaces. The eggs hatch in the intestine, and the larvae migrate through the liver and lungs before returning to the intestines to mature. Potential complications include:

  • Intestinal blockage — Heavy infestations can cause intestinal blockage, leading to colic, poor growth, and possible intestinal rupture.
  • Respiratory issues — During the migratory phase, larvae can cause respiratory problems, such as coughing and nasal discharge.
  • Nutritional deficiencies — Infestations can lead to poor nutrient absorption, resulting in weight loss and a dull coat.

Bots in horses

Botflies lay their eggs on the horse’s coat. When the horse licks or bites at the itchy areas, the eggs hatch, and the larvae migrate through the mouth tissues to the stomach where they attach. The attached larvae can cause irritation, leading to ulcers, gastritis, and inflammation. 

Tapeworms in horses

Horses become infected with tapeworms by ingesting oribatid mites while grazing. Once ingested, the tapeworm larvae mature to their adult stage in the horse’s intestine, where they attach to the intestinal wall, causing inflammation and irritation. Heavy infestations can lead to colic, weight loss, and digestive disturbances. Tapeworms that accumulate at the junction between the small intestine and cecum can cause an impaction or a telescoping of the intestine (i.e., intussusception).

Pinworms in horses

Horses are infected by pinworms when they ingest contaminated feed, water, or surfaces, or when they lick or bite affected areas because of itching. Once ingested, the eggs hatch in the horse’s intestine and mature. Adult female pinworms migrate to the horse’s anus to lay their eggs, typically attaching them to the skin around the anus in a sticky, yellow substance. This causes intense itching, leading horses to rub their tails and hindquarters, which can result in hair loss and skin irritation.

Ticks and horses

Various species, such as the western black-legged tick, can attach to your horse, leading to issues such as irritation, bite-site infection, and the transmission of diseases such as Lyme disease. 

Flies and horses

Stable flies, horse flies, deer flies, and black flies are prevalent in some seasons, causing irritation and stress, and some species can also transmit diseases such as equine infectious anemia (EIA).

Preventing parasites in horses

Recommendations to protect your horse from parasites include:

  • Fecal egg counts — Conduct regular fecal egg counts to monitor parasite levels.
  • Regular deworming — Work with our Rustebakke Veterinary Service team to develop an appropriate deworming schedule based on fecal egg counts. 
  • Pasture management — Regularly remove manure to reduce parasite larvae in pastures, allow pastures to rest, and reduce parasite load by rotating grazing areas. In addition, avoid overgrazing to reduce parasite transmission.
  • Stable hygiene — Keep stalls clean and dry to minimize parasite eggs and larvae, and ensure water sources are clean and not contaminated with feces.
  • Fly control — Use fly masks, fly sheets, and insect repellents to protect against flies.
  • Tick control — Regularly check for and remove ticks, and use tick prevention products as recommended by our veterinary team.
  • Health monitoring — Schedule regular veterinary wellness exams to check for signs of parasitic infections and ensure your horse remains healthy.

Parasite prevention and management are essential for maintaining your horse’s health and well-being. Contact our Rustebakke Veterinary Service team so we can help determine an appropriate deworming schedule for your equine friend.