Barber's Pole Worm

Barber's pole worm is a blood-feeding roundworm, Haemonchus contortus, that lives in the abomasum, the true stomach of sheep, goats and alpacas. It attaches to the stomach lining and drinks blood. The name comes from the female worm: her white reproductive tract spirals around a gut full of red blood, giving her the striped look of an old barber's pole. Adult females reach 20 to 30 mm and are visible to the naked eye in a post-mortem, but in a living animal the diagnosis comes from a dung sample and a blood or eyelid check, not from spotting worms.

The danger lies in the numbers. A single worm removes only about 0.03 to 0.05 ml of blood per day, but one female can lay thousands of eggs daily, so burdens build within weeks. A sheep carrying several thousand worms can lose in the region of 250 ml of blood every day. The animal is bleeding internally, slowly and invisibly, which is why the classic picture is anaemia rather than diarrhoea. Owners who expect a scouring animal often miss it entirely.

Signs to watch for

• Pale gums and pale membranes inside the lower eyelid instead of a healthy pink
• Lethargy, lagging behind the group, or flopping down when the animal is moved briskly
• A soft fluid swelling under the jaw, known as bottle jaw
• Weight loss, poor growth in lambs and kids, and a dropping fleece or coat condition
• Sudden death in a heavily infected animal that looked passable the day before

Eggs pass out in the dung, hatch on pasture and develop into infective larvae that are swallowed as your animals graze. Warm, humid weather speeds this up, so the parasite is worst in summer rainfall regions and in unusually wet summers, and in cooler climates larvae can lie dormant inside the animal over winter and surge in spring. Young weaned animals and ewes or does around lambing and kidding are at highest risk, and poor nutrition makes disease more severe. Adult animals never build strong lasting immunity, so age is no protection.

Control has moved away from dosing everything on a calendar. Faecal egg counts show how much of a burden a group is carrying, and infections with this worm typically produce strikingly high counts. Many vets also use the FAMACHA chart, developed at the University of Pretoria in South Africa, which scores the colour of the membrane inside the lower eyelid from 1 (red, no anaemia) to 5 (white, severe anaemia) so only the animals that need treatment get it. Validation work in sheep and goats in the southern United States supports its use on farms where this worm is the main problem. The reason for the restraint is resistance: worms that survive repeated dosing pass that survival on, and the Merck Veterinary Manual notes that anthelmintic resistance in small ruminant worms is now widespread, with selective treatment strategies recommended to slow it. Treating new arrivals while they are still in quarantine is one of the few reliable ways to avoid importing resistant worms onto your land.

Which wormers still work, and how often to test, varies by region and by farm, so this is general background rather than a treatment plan. If an animal is pale, weak or has swelling under the jaw, treat it as urgent and speak to a vet the same day. A vet can run egg counts, check red blood cell levels and build a monitoring plan that suits your grazing and climate.