Pinworms do not migrate or travel through the body. Adult pinworms reside in the rectum. When the horse is sleeping or resting, adult worms crawl out to the surface and lay sticky eggs around the horse’s anus, then crawl back into the rectum. The infectious eggs fall onto the pasture and are ingested by other horses while grazing. It takes 4 to 5 months for pinworm eggs to develop into adult worms, a process that takes place in the large intestine. The main symptom of pinworm infection is itching around the base of the tail. The itching is bothersome but not dangerous. Since adult pinworms always remain in the intestines and do not migrate through the body, the discomfort caused by this worm is minimal.
It is often reported that worms are found in the manure, even though deworming is done regularly. The worms are then spontaneously expelled with the manure. Under Dutch conditions, pinworms do not play a major role. Please note that other causes can also lead to itching at the base of the tail. If your horse excessively rubs or scratches its tail, we recommend contacting your veterinarian. Since the eggs are not deposited in the manure but on the skin around the anus, eggs are rarely found in fecal tests. The effectiveness of ivermectin against pinworms is sometimes insufficient, so these worms may still be found in the manure after treatment.
In our fecal tests, we routinely check for pinworms, but their eggs are not often found in the manure. If a fecal test shows your horse is infected with pinworms, we will provide you with a personalized treatment plan. This way, your horse’s health comes first and unnecessary deworming can be avoided. Even if you suspect a pinworm infection, you can contact us. Please feel free to contact our team if you have any questions; we are happy to help!
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