Parasite management in livestock involves the control of internal parasites (worms) and external parasites (ticks, lice, mites, flies) through integrated strategies. Internal parasites are the most significant health and production concern for grazing livestock in many regions. The goal of parasite management is to maintain parasite burdens below the level that causes clinical disease or production loss, not to eliminate parasites entirely.
The most economically significant internal parasites of ruminants are barber pole worm (Haemonchus contortus), brown stomach worm (Teladorsagia circumcincta), and intestinal worms including Cooperia and Nematodirus. Haemonchus contortus is a blood-feeding parasite that causes anemia, bottle jaw (submandibular edema), and death in sheep and goats. The barber pole worm is particularly problematic in warm, moist climates where the free-living larval stages survive on Pasture Rotation for extended periods.
Quantitative parasite monitoring is done through fecal egg counts, where a known mass of feces is mixed with a flotation solution and examined under a microscope. The McMaster counting method is the standard technique, with results expressed as eggs per gram. A count above 500 eggs per gram in sheep or goats typically indicates a need for treatment in most management systems. Regular fecal testing (every 4 to 6 weeks during the grazing season) allows targeted treatment of only those animals that need it.
Refugia-based deworming maintains a population of worms not exposed to dewormers, delaying the development of resistant parasites. The FAMACHA system, which scores sheep and goats based on the color of the lower eyelid mucous membrane, identifies animals that need deworming based on anemia caused by Haemonchus. Anthelmintic drugs are rotated by chemical class to slow resistance.
Ticks cause direct damage through blood loss and transmit diseases including anaplasmosis and Lyme disease. Lice cause irritation, hair loss, and reduced weight gain. Fly control includes pour-on insecticides, insecticide ear tags, and biological control through dung beetles and parasitic wasps.