THE PARASITES
More than 150 species of internal parasites can infect horses, but only a handful pose the most serious health threats.
*Most horses develop immunity by the time they are a year old.
THE LIFE CYCLE
Warm, moist weather sets the parasite life cycle in motion. It can occur in the spring, summer and fall, depending on climate. Some parasites, such as ascarids, will stay in the body for weeks. Others, such as
