Cause
Horses become infected with strongyles when they eat infective strongyle eggs passed in the feces of another horse with the infection. For the eggs to be infective, they must continue to develop for a period of one to three weeks; it is not until the eggs have developed into the infective larval stage, or L3, that they will cause infection in a horse that ingests them. Once ingested, the L3 larvae migrate to the cecum and colon, which make up the majority of a horse's large intestine.