All horses can be infected regularly with internal parasites that can be picked up from paddocks or by ingesting bot (fly) eggs. Worming is particularly important for young or older horses that are more susceptible to the parasites. Intestinal parasites can cause digestive upsets, anemia, dull coat, poor appetite, itchy tail, colic and even death if left untreated. Popular horse wormers include; Ammo Allwormer, Equest plus tape, Equimax LV, Eraquell and Strategy T.