barber pole (hemonchus contortus) internal parasites
Barber Pole stomach worms (Hemonchus contortus) are very dangerous to sheep and goats. The worms live in the abomasum (stomach), sucking blood from its lining. Each worm can ingest 0.05 ml of blood per day, a moderate load of worms (approximately 1000) can take 50 ml of blood from the animal per day. This parasitism and chronic blood loss results in poor growth, bottle jaw, weakness, lethargy and pale mucous membranes. In severe cases, sheep or goats may drop dead on pasture without any other signs, due to the heavy blood loss caused by the Hemonchus worms.
The life cycle of these parasites is very simple. Adult females can lay up to 10,000 eggs per day, which enter the environment via the manure of infected animals. The eggs hatch and mature to infective larvae in 1 to 3 weeks, depending on the weather. These larvae crawl onto the grass to be eaten by the sheep or goats. Once ingested, it only takes 21 to 28 days for them to mature into adults, who will then suck blood from the stomach lining. Warm temperatures speed up the hatching and maturation of the larvae, and moisture helps release the larvae from the fecal ball. It also allows the larvae to stay near the top of the grass blades where they are more likely to be eaten. The most risky pastures are those covered by dew on a sunny day. If the right warm and moist conditions are met, the larvae can live on pasture for months, increasing the larval contamination on the pasture each day. Control measures combine fecal parasite testing with a strategic deworming program and pasture management. There is growing resistance of Hemonchus spp to some common anthelminitic (deworming) drugs, which makes the fecal analysis before and after deworming of paramount importance.
,2 Handbook for the Control of Internal Parasites of Sheep, July 26, 2009. Andrew Peregrine, Paula Menzies et al. Department of Population Medicine, Ontario Veterinary College, University of Guelph, Guelph, ON, N1G 2W1