Equine Sciences Extension Program
Pin Worms - Internal Parasites
Table of Contents
Pin worms are less harmful than the parasites discussed previously. They cause rectal irritations primarily.
How your horse becomes infected: Horses become infected by consuming feed and water contaminated with infective worm eggs.
Health effects: Immature worms can produce severe damage to the mucous membrane in the upper large intestine. The details of the life cycle of these worms are not completely known. It is known that the worm lives in the lower intestine where they produce a moderate inflammation. The females leave the rectum and deposit their eggs on the skin around the anus, causing an intense itching which the horse attempts to relieve by rubbing the tail.