What Worms Can Horses Carry?

Horses, like humans, can contract several different types of parasites. Worms can cause horses considerable discomfort and illness if left untreated. Although worms vary in size and effect, all are preventable with a regular deworming schedule. Knowing what worms most commonly affect equine will help you make the right decision on the type of deworming product to choose. If you suspect that your horse has worms, take it to the veterinarian immediately for a checkup. Prompt treatment is essential to reduce the chance of sickness or fatality.

  1. Strongyles

    • Stronglyles -- also called blood worms, red worms and palisade worms -- are the most common and most dangerous parasites for horses. They cause damage in both the larvae and adult stages of their lives. Adult stronglyles suck the horse's blood and damage its intestinal lining, causing diarrhea, anemia and overall weakness. As larvae, stronglyles can damage a horse's intestines, mainly affecting the large intestine. Stronglyles can also cause aneurysms and death.

    Roundworms

    • Roundworms or ascarids are large worms that migrate throughout a horse's body, mainly affecting young foals. These exceptionally large worms normally grow to between 8 and 10 inches long. After a horse swallows roundworm larvae, they travel in the bloodstream to the liver and heart. From the heart, the worms migrate to the lungs. The horse will cough up the worms and then swallow them again. Once swallowed, the worms head to the intestine, where they mature. They cause the most damage in the lungs, resulting in pneumonia.

    Pin Worms

    • Pin worms mainly cause external issues on a horse, although the adult worms live mainly inside the horse's bowels. Problems with pin worms start when a female pin worm lays eggs around a horse's anus, causing irritation and severe itching. Because of the itchiness, horses rub their tails and surrounding skin on nearby objects. This rubbing can result in a dangerous infection around the tail area.

    Thread Worms

    • Thread worms are found in mare's milk and affect nursing foals, passing through the mare and into the foal's small intestine. The worms may be present in a mare four to 40 days after foaling. They will affect the foal at about two or three weeks of age, causing diarrhea and indigestion.