Managing Haemonchus (Barber’s Pole worm) in Cumbria’s Flocks

By vet Catherine Davies 

Haemonchus contortus is a parasitic roundworm that resides in the abomasum (true stomach) of sheep and goats. Unlike most gut worms, Haemonchus feeds on blood, causing anaemia, sudden death, bottle jaw (fluid under the jaw), and significant production losses. A sheep carrying 5000 adult H.contortus worms can lose up to 250 ml of blood per day. It gets its nickname from the red-and-white striped appearance of the adult female worm, resembling a barber’s pole.

Historically it has been more common in warmer climates, however, Haemonchus is now becoming a growing concern in the UK. Especially, in parts of Cumbria where mild, wet summers and warmer autumns are becoming more frequent. These conditions provide an ideal breeding ground for the parasite, leading to longer transmission seasons and unexpected outbreaks. Outbreaks have been confirmed as high as Inverness.

In some years, outbreaks have occurred as late as November, catching farmers off guard. As temperatures rise each year, this pattern is likely to continue, making seasonal planning even more important.

Why is it a growing threat? 

While Haemonchus has been present in the UK for decades, its increasing prominence is linked to several key factors:

• Climate change: Warmer average temperatures are extending the grazing season and enabling larvae to survive longer on pasture.
• Anthelmintic resistance: Like other worms, Haemonchus is developing resistance to commonly used wormers, making control more difficult.
• Subtle symptoms: Haemonchus often causes anaemia without diarrhoea, meaning signs can be missed until it’s too late.

Spotting the signs. 

Early detection is critical. Farmers should be alert for:

• Pale gums and eye membranes (anaemia)
• Weakness or collapse, especially in lambs
• Bottle jaw (oedema)
• Poor growth or weight loss
• Sudden deaths, particularly after warm, wet weather

The FAMACHA eye colour chart – is widely used in countries like South Africa and Australia – this is a tool for identifying anaemic animals due to Haemonchus and is used in conjunction with worm egg counts.

Diagnosis and testing

Routine worm egg counts (WECs) are a valuable tool for monitoring parasite levels, but they can’t distinguish Haemonchus eggs from other strongyle-type eggs under the microscope. Therefore, a targeted WEC with speciation is required. In some laboratories, a special staining technique or larval differentiation can help confirm its presence. Additionally, adult Haemonchus worms – recognisable by their distinctive red-and-white ‘barber’s pole’ appearance – can often be seen in the abomasum during a post-mortem examination.

Control strategies

Managing Haemonchus effectively requires a multi-pronged approach as follows:

• Strategic worming: Avoid blanket treatments. Targeted selective treatment helps preserve anthelmintic effectiveness and reduces resistance pressure.
• Drench checks: Use faecal egg count reduction tests (FECRTs) to ensure your wormers are still effective.
• Pasture management: Rotate grazing and rest fields to reduce larval burden. Short, heavily grazed pastures are high-risk areas — especially if used repeatedly without sufficient rest. Regular sward measurement with a plate meter or sward stick can help with pasture planning and worm risk management.
• Monitor ewes pre-lambing: Lactating ewes can experience a worm egg count rise, seeding the pasture with infective larvae for lambs – including Haemonchus if present.
• Vaccination: A vaccine is used successfully in parts of Australia and South Africa due to high levels of resistance to wormers. However, this is not licensed in the UK unless there is a special import certificate from the veterinary medicine directorate. 

Looking ahead

The rise of Haemonchus in Cumbria and other northern regions needs to be on the forefront of our minds. With anthelmintic resistance on the rise, we can’t rely on drenches alone. Proactive testing, careful monitoring, and sustainable parasite control plans are essential.