Warm weather impacts the risk of Barber’s pole worm

Outbreaks of haemonchosis (Barber’s pole worm) have been increasing in recent years in the UK. APHA is warning farmers to be on the lookout for signs of infection in areas with rainfall following the recent heatwaves.

The dry conditions across much of GB have resulted in reduced grass growth and reduced challenge from gastrointestinal nematode parasites that can affect grazing animals. However, once rainfall occurs, the risk of disease increases, as has been seen in some flocks already.

With bluetongue virus circulating, it is important to remain vigilant to signs of disease, as concurrent infections (for example, a high worm burden and bluetongue disease) can lead to increased mortality rates.

Adult haemonchus worms, and those approaching adulthood, can remove large quantities of blood from an infected sheep, with as few as 500 worms being able to cause disease.

Unlike other species, this worm can produce 5,000–15,000 eggs per day (compared with 400 eggs for Teladorsagia roundworm) and has a short life cycle of 20 days.

Clinical signs, which can appear suddenly and resemble liver fluke infections, include:

• Weak animals that are likely to collapse if gathered
• Ill thrift with no diarrhoea (possible slight constipation)
• Pale mucus membranes (anaemia)
• Quick, shallow breathing and increased heart rate
• Sudden death
• Bottle jaw

There is little immunity to this parasite in lambs, and immunity in adults can be overwhelmed by a large number of worms.

High egg counts may be seen with faecal egg counts (FECs), but as the eggs are similar to other species of worm, accurate diagnosis is difficult with standard microscope techniques and without supporting confirmation.

Not all high FECs will be due to haemonchus, and it is crucial to use tests correctly to inform management and treatment decisions.

To make an accurate diagnosis, fluorescence testing using peanut agglutinin is needed, or a post-mortem examination.

APHA is offering discounted differential fluorescence testing to detect haemonchus eggs; this can be arranged through your vet.

Speak to your vet or registered animal medicines adviser (RAMA/SQP) who can arrange testing and advise on the most appropriate product choice and any follow-up testing to ensure that treatment has been effective.

While haemonchus mainly affects sheep and goats, it can be ingested by cattle and there are reports of wildlife, e.g. red deer, being a reservoir. Bear this in mind when investigating outbreaks and looking for sources of the parasite.

Do not overlook the importance of quarantine, which can help prevent bringing in the parasite with new or returning livestock.