Barber's Pole Worm

Barber's pole worm is the everyday name for Haemonchus contortus, a blood-feeding roundworm that lives in the abomasum, the true stomach, of sheep, goats and alpacas. It attaches to the stomach wall and drinks blood directly, rather than simply irritating the gut lining the way some other worms do. You won't spot the worms themselves in a living animal. A vet diagnoses the problem by checking a dung sample for eggs and looking at the colour of the gums or the inside of the lower eyelid for signs of blood loss.

The danger here is scale, not size. A single worm can draw up to roughly 0.05 ml of blood a day, and a female worm may lay thousands of eggs daily, so numbers build quickly once conditions suit the parasite. In a heavy infection the combined blood loss can climb past 100 ml a day, enough to cause severe anaemia or even sudden death in an animal that looked only slightly off the day before. Because the damage is blood loss rather than gut irritation, the classic picture is a pale, weak animal rather than one with diarrhoea, which is why owners waiting for scouring can miss it entirely.

Signs worth watching for include:

• Pale gums or a pale lining inside the lower eyelid, instead of a healthy pink
• Lethargy, lagging behind the group, or collapsing when moved briskly
• A soft swelling under the jaw, known as bottle jaw
• Weight loss, poor growth in young animals, or a decline in coat or fleece condition
• Sudden death in an animal that had seemed only mildly unwell

Eggs pass out in the dung and, in warm wet weather, hatch into infective larvae on pasture within days, ready to be swallowed as animals graze. This worm thrives in warmer, humid conditions and slows or goes dormant once it turns cold, though its larvae can still sit alive on grass for weeks or months waiting for warmer weather to return. That is why disease tends to flare in wet summers and, in cooler climates, can surge again once spring arrives.

Control has shifted away from dosing every animal on a fixed schedule. A faecal egg count shows how heavy a group's burden really is, and many farms also use the FAMACHA system, which scores the colour of the lower eyelid from 1 (healthy red) to 5 (very pale) so that only the animals that need treatment get it. This was validated for exactly this purpose on farms across the southern United States, where the score correlated well with both anaemia and egg counts. Elsewhere the picture is less tidy: more recent work in a different setting found no clear link between eyelid score and faecal egg counts, a reminder that this tool works best where barber's pole worm is genuinely the dominant parasite, and that a vet may want to combine it with other checks. Resistance to dewormers in this parasite is now widespread across drug classes, which is exactly why treating only the animals that clearly need it, rather than the whole group, matters for keeping the remaining drugs effective.

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 an egg count, check for anaemia, and help you build a monitoring plan that fits your animals and your climate.