SHEEP farmers are being urged to remain vigilant for signs of Haemonchus contortus infection after reports suggest the parasite is spreading across the UK.

Vet Gina Rigby from Cross Counties Farm Vets in Northamptonshire, part of the VetPartners group, is encouraging farmers to familiarise themselves with signs of Haemonchus and regularly check their sheep for infection.

Her plea comes following an alert from the Sustainable Control of Parasites in Sheep (SCOPS) group which said recent testing suggests an increase in cases of Haemonchus infection with the parasite appearing further north across the UK.

“Haemonchus contortus, or Barber’s Pole worm as it’s commonly known, is becoming more and more prevalent in the UK as our weather patterns change,” says Mrs Rigby.

“Historically, if we had very cold, harsh winters, a lot of the Haemonchus larvae would be killed off, but now we’re finding that they’re overwintering – both on pasture and in the ewes – which means we’re seeing infection earlier in the year than we were before.”

She says Haemonchus is different from other gastrointestinal worms and, as such, it causes different symptoms.

“Haemonchus is a blood-sucking worm which can cause anaemia, and unless a sheep has a mixed infection with other gastrointestinal worms, it doesn’t cause scour,” she adds.

“This means sheep farmers are often caught out by it because they’re not seeing the classic signs of worms, like mucky back-ends, on their sheep.”

She says the symptoms of Haemonchus infection depend on whether the sheep is suffering from acute, sub-acute, or chronic infection.

“Acute infection is caused by an animal ingesting a lot of infective larvae in a very short period of time, and the signs include sudden death, rapid breathing, and pale mucus membranes which can be seen by looking at the inside of the lower eyelid,” adds Mrs Rigby.

“Sub-acute infection isn’t always as obvious, and often farmers get this confused with liver fluke, because it causes bottle jaw (swelling under the jaw), while chronic infection presents as more of a failure to thrive with weight loss, poor body condition, and lethargy – along with the signs of anaemia.”

To monitor for Haemonchus, Mrs Rigby recommends looking out for clinical signs of infection, FAMACHA© scoring, worm egg counting, and carrying out a post-mortem examination on any dead animals.

“FAMACHA scoring is a colour chart to compare with the colour of the membranes of the lower eyelid to assess for anaemia caused by Haemonchus; it’s relatively easy to do when you’re already running animals through the race for other reasons,” explains Mrs Rigby.

“Worm egg counts are also useful to identify the presence of worms, however ‘in house’ counts can’t easily differentiate Haemonchus from other worm species, so if you suspect you’ve got a problem, you can send a sample off to the lab for worm species identification.”

If Haemonchus is identified, Mrs Rigby says farmers should speak to their vet to discuss an appropriate treatment plan.

“Finding Haemonchus in a sample doesn’t necessarily mean clinical disease is present on your farm,” she adds.

“Speak to your vet about treatment – both in terms of product choice and which animals need it, or whether vaccination might be an option on your farm.”

Read more about Gina Rigby here.