Haemonchosis in Sheep: Barber Pole Worm Signs, Anemia, and Deworming
- See your vet immediately if a sheep has pale eyelids, weakness, collapse, bottle jaw, or sudden weight loss during parasite season.
- Haemonchosis is caused by Haemonchus contortus, the barber pole worm, a blood-feeding stomach parasite that can cause severe anemia and death.
- Many sheep do not develop diarrhea. Pale lower eyelids, poor thrift, and swelling under the jaw can be more important warning signs.
- Diagnosis often combines FAMACHA eye color scoring, packed cell volume or other bloodwork, fecal testing, and flock history.
- Deworming should be targeted, not automatic. Your vet may recommend selective treatment and follow-up fecal egg count reduction testing because drug resistance is common.
What Is Haemonchosis in Sheep?
Haemonchosis is a parasitic disease caused by Haemonchus contortus, commonly called the barber pole worm. This worm lives in the abomasum, or true stomach, of sheep and feeds on blood. Heavy infections can cause marked anemia, weakness, poor growth, and death, especially in lambs and periparturient ewes.
This parasite is one of the most important and damaging gastrointestinal worms in sheep. It tends to be a bigger problem in warm, humid conditions and on contaminated pasture. Sheep can look normal early on, then decline quickly once blood loss becomes severe.
One tricky part is that affected sheep may not have obvious diarrhea. Instead, pet parents and flock managers often notice pale eyelids, reduced stamina, weight loss, or "bottle jaw," which is soft swelling under the lower jaw linked to low blood protein and anemia. Because the disease can progress fast, early veterinary guidance matters.
Symptoms of Haemonchosis in Sheep
- Pale lower eyelids or gums
- Weakness, lagging behind, or exercise intolerance
- Bottle jaw
- Weight loss or poor growth
- Poor body condition or rough fleece
- Sudden collapse or death
- Dark or normal manure with few digestive signs
See your vet immediately if a sheep has very pale eyelids, bottle jaw, weakness, rapid breathing, inability to stand, or sudden decline. Those signs can mean dangerous anemia. In flock situations, one sick sheep may also signal a broader pasture or parasite-control problem, so your vet may want to assess more than one animal.
What Causes Haemonchosis in Sheep?
Haemonchosis happens when sheep ingest infective larvae of Haemonchus contortus while grazing. Eggs are passed in manure, then develop on pasture into larvae that climb only a short distance up forage. Sheep pick them up close to the ground, especially on overgrazed, moist pasture.
Warm weather and adequate moisture strongly favor this parasite. Risk often rises in spring and summer, though local climate matters. Young lambs, lactating or late-gestation ewes, and animals under nutritional or transport stress may be more vulnerable.
Another major cause of ongoing problems is anthelmintic resistance. In many US flocks, barber pole worms are no longer reliably controlled by every dewormer class. Repeated whole-flock treatment, underdosing, and treating on a fixed schedule can all increase resistance pressure. That is why your vet may recommend targeted selective treatment, pasture management, and follow-up fecal testing instead of routine blanket deworming.
How Is Haemonchosis in Sheep Diagnosed?
Your vet usually diagnoses haemonchosis by combining history, physical exam findings, and testing. Important clues include pale mucous membranes, bottle jaw, poor thrift, recent pasture exposure, and the time of year. FAMACHA scoring can help estimate anemia by comparing lower eyelid color to a standardized chart, but it works best as part of a larger plan rather than as a stand-alone diagnosis.
Fecal flotation or fecal egg counts can show strongyle-type eggs, and fecal egg count reduction testing can help your vet check whether a dewormer is still working on your farm. Bloodwork, especially packed cell volume or hematocrit, helps measure how severe the anemia is. In very early disease, eggs may not yet be present even when the sheep is already sick, so test results must be interpreted with the clinical picture.
When signs are severe, your vet may also look for other causes of anemia, weakness, or swelling, including lice, nutritional problems, liver disease, or other parasites. In some cases, diagnosis is confirmed after treatment response or postmortem examination in flock outbreaks.
Treatment Options for Haemonchosis in Sheep
Spectrum of Care means you have options. Here are treatment tiers at different price points.
Budget-Conscious Care
- Farm-call or herd-level veterinary guidance when available
- Targeted selective deworming of clinically affected sheep based on FAMACHA score and exam findings
- Basic fecal testing or pooled fecal egg count when individual testing is not feasible
- Supportive care such as reduced stress, easy access to water, and movement to lower-risk pasture or dry lot
- Recheck plan to monitor eyelid color, body condition, and response
Recommended Standard Treatment
- Veterinary exam with FAMACHA assessment and body condition review
- Individual fecal egg count or fecal flotation plus bloodwork such as packed cell volume or hematocrit
- Targeted deworming using a product and dose selected by your vet for sheep and local resistance patterns
- Follow-up fecal egg count reduction testing or scheduled recheck to confirm response
- Pasture-management plan, nutrition review, and identification of high-risk animals
Advanced / Critical Care
- Urgent veterinary stabilization for severe anemia, weakness, recumbency, or collapse
- Expanded bloodwork and close monitoring of hydration, oxygenation, and cardiovascular status
- Intensive supportive care such as fluids, nutritional support, and in select referral cases blood transfusion-level care
- Aggressive flock investigation with individual and post-treatment fecal testing
- Detailed parasite-control redesign for resistant or high-loss farms
Cost estimates as of 2026-03. Actual costs vary by location, clinic, and individual case.
Questions to Ask Your Vet About Haemonchosis in Sheep
Bring these questions to your vet appointment to get the most out of your visit.
- Does this sheep look anemic enough to need urgent treatment today?
- Which dewormers are still likely to work on sheep in our area and on our farm?
- Should we run fecal egg counts or a fecal egg count reduction test before and after treatment?
- How should we use FAMACHA scoring correctly, and how often should we check the flock?
- Which sheep should be treated now, and which ones should be left untreated to help slow resistance?
- Do we need bloodwork such as packed cell volume to judge how severe the anemia is?
- What pasture, stocking, and nutrition changes would lower our parasite pressure this season?
- Are there sheep in this flock that should be culled or not kept for breeding because of repeated parasite problems?
How to Prevent Haemonchosis in Sheep
Prevention works best when it combines monitoring, selective treatment, and pasture management. Your vet may recommend regular FAMACHA checks during high-risk weather, especially in lambs and around lambing. Sheep with pale eyelids, poor body condition, or repeated parasite problems may need closer follow-up than the rest of the flock.
Avoid relying on calendar-based whole-flock deworming alone. That approach can speed up resistance. Instead, many flocks do better with targeted selective treatment, accurate dosing based on current weight, and fecal egg count reduction testing to confirm that the chosen product still works. Underdosing is a common reason control programs fail.
Pasture strategy matters too. Overgrazing increases exposure because infective larvae stay low on forage. Resting pastures, reducing stocking pressure, improving nutrition, and separating the most vulnerable groups can all help. Some farms also select breeding animals that stay healthier under parasite pressure, which can improve flock resilience over time.