Intestinal Parasites of the Horse
The horse has a number of different parasites which have evolved to live in its intestine. These worms are highly specialised to live and reproduce within the horse. Most can not live in other species of animal
Almost every horse alive will have at least one parasitic worm in its body. It is important to realise that often these worms are present in low numbers and cause the horse no ill-effects. Occasionally, however, horses develop heavy worm burdens which can be damaging and even fatal. Domestication of the horse, forcing it to graze in enclosed fields, close to other horses has increased the likelihood of heavy burdens developing. The section entitled "How worms cause disease" describes the harmful effects of heavy worm burdens.