Diagnosis, Treatment, and Prevention of Common Small Ruminant Parasites

Abstract

External parasites of small ruminants include lice, keds and mange mites. They cause pruritus, fleece damage, and in some instances blood loss anemia. The most important internal parasite of sheep and goats is Haemonchus, a blood sucking strongyle that can kill animals on contaminated pasture in a matter of weeks. Overuse of dewormers has caused the development of parasite resistance, and currently recommended programs emphasize selective treatment and eventual culling of animals that show severe clinical signs. Untreated animals are left in the herd to provide unselected parasites in refugia. Other strongyle species contribute to production loss by causing weight loss and diarrhea. Tapeworms are of minimal clinical importance but, regionally, liver flukes cause ill thrift or death. Fencing off ponds and stream is often more effective than deworming for fluke control. In regions where whitetail deer abound on pastures, the meningeal worm Parelaphostrongylus tenuis causes neurologic disease and sporadic losses of small ruminants and guard llamas.