Pinworms are small parasites that infect the digestive tract of horses. Adult pinworms lay eggs around the horse's anus, causing irritation and itching. The most common symptom of a pinworm infection is tail rubbing, which can cause stress, sores and loss of hair on the rear end of your horse. Pinworms don't generally cause severe health problems by themselves, but the irritation can cause your horse distress. Pinworms should be treated as soon as possible.
Initiate a regular program of deworming medication. Seek the advice of your veterinarian. She can help you choose the best dewormer for your area and situation.
Dispose of manure properly. Manure should be spread or composted in non-grazing areas.
Place feed in containers off the ground to avoid faeces mixing with food.
Change water often. Water should be clean at all times to help prevent infection.
Pinworms, as with other parasites, can become resistant to deworming medication. Discuss a rotation program with your vet.