Haemonchus: Don’t panic – test first to be sure
12th June 2025
Sheep farmers have been encouraged to stay alert and informed as Haemonchus contortus – commonly known as Barber’s Pole worm – gains more attention across the UK.
SCOPS (Sustainable Control of Parasites in Sheep) said that while recent reports and testing suggest increased interest and possible cases of haemonchosis (disease associated with Haemonchus infections) appearing further north across the country, the reasons are not fully understood yet.
Climate change with warmer winter temperatures may allow the parasite to survive on pasture, and drier, warmer springs create ideal conditions for it to take hold earlier in the spring.
SCOPS has also stressed the importance of accurate diagnosis and calm, evidence-based decision-making to support effective parasite control on farms.
“While Haemonchus can cause serious issues in flocks, it’s important that you do not panic.
“We’re seeing more interest and investigation into this parasite, which is positive, but we must avoid jumping to conclusions or reverting to blanket treatments, especially in adult ewes that could undermine responsible and sustainable parasite control,” said Nerys Wright, SCOPS technical adviser.
What is Haemonchus contortus?
Haemonchus is one of a number of different roundworms that are found in sheep in the UK.
Unlike many other roundworms, it does not typically cause diarrhoea. It is a blood-sucking roundworm that resides in the stomach of sheep.
It can lead to anaemia (pale gums and eyelids), bottle jaw (swelling under the jaw), lethargy, weight loss, and, in advanced cases, sudden death.
Presence of Haemonchus eggs in a faecal egg count (FEC) does not always indicate haemonchosis (clinical disease).
Tips for Haemonchus diagnosis:
- Test first: SCOPS is encouraging farmers to work closely with their vets and advisers to take a test-first approach. The first step would be to carry out a faecal egg count (FEC) to determine the strongyle count.
- Species identification: a high strongyle count (several thousand eggs per gram; EPG) is indicative but cannot confirm the presence of Haemonchus. Species testing, such as peanut agglutinin (PNA) staining, must be submitted via your vet and identifies the proportion of strongyle eggs that are Haemonchus. This test is available through APHA and is currently discounted at £20 per sample.
- FAMACHA scoring: a useful tool for assessing anaemia in potentially affected animals. Farmers can evaluate the colour of the lower eyelid (conjunctiva) using a scale from 1 (red, not anaemic) to 5 (white, severely anaemic). The paler the eyelid, the more anaemic the animal is likely to be.
- Never waste a dead sheep: post-mortems can identify a range of health issues. Unlike other roundworms, adult Haemonchus worms can be easily seen by eye in the stomach. Combined with signs such as pale carcases and weight loss, this can confirm the presence of disease.
Ms Wright added that product choice is “crucial”. She continued: “We have limited resistance data for Haemonchus in the UK, so using newer or narrow-spectrum actives without confirmed need could lead to problems in the future.
“Treatment decisions should be based on diagnostics and tailored to the farm’s history of product use, as well as other parasite burdens and treatments. For example, if the farm is affected by fluke and regularly uses a Closantel-based product, it would be advisable to consider alternative wormers to help safeguard the efficacy of those fluke treatments.”
SCOPS also reminds farmers that pasture conditions, particularly during dry spells, can influence parasite dynamics. Regular monitoring, strategic treatment, and robust quarantine protocols remain key to managing risk.
For further guidance on Haemonchus, including treatment strategies and quarantine advice, visit the SCOPS website.
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