Horses can fall victim to several intestinal parasites, including strongyles, ascarids, and pinworms. Strongyles, in particular, can be classified into two categories large strongyles and small strongyles. Large strongyles are notorious for causing severe damage to blood vessels, leading to serious health problems. Ascarids, or roundworms, primarily affect young horses and can cause colic, impaction, and stunted growth. Pinworms, while generally less harmful, can cause irritation around the tail area, leading to rubbing and skin problems.