Sheep farmers are being urged to look out for signs of the blood sucking worm Haemonchus contortus as the weather improves.

This prolific worm, otherwise known as the Barber’s Pole worm, can contaminate pastures rapidly and affects both lambs and adult sheep quickly, leading to devastating losses.

Unlike other gastrointestinal worms, which cause scouring, Haemonchus often presents sick looking sheep with no scouring. This can lead to high levels of mortality if it is not identified quickly.

Emily Gascoigne, a vet with Synergy Farm Health in Dorset, says the parasite is clever as it is a prolific breeder, which can be destructive if not managed.

She has seen many cases in the south west: "I've been at Synergy since 2012 and 2017 was the worst year I’ve ever seen cases of Haemonchus in both commercial and small holder flocks. These lambs are not scouring and dead animals may be the first indication of infection you see.”

- Symptoms

Heavy Haemonchus burdens can lead to anaemia, as each worm is able to remove about 0.05ml of blood a day. For sheep infected with 5,000 worms, this equates to 250ml of blood loss a day1.

One of the first clues of Haemonchus infection is eye colour in sheep. Ms Gascoigne said: “Normally the third eyelid in sheep is nice and pink. However, if Haemonchus is present, it will be white and pale, indicating anaemia. It is a good monitoring tool.”

- Control

The best way to monitor for Haemonchus is to conduct regular faecal egg count samples from lambs and periodically, adult sheep throughout the grazing season.

Ms Gascoigne said: “Whereas a high worm egg count for other gastrointestinal worms may be in the hundreds, a tell-tale sign of Haemonchus is sky high eggs counts over 10,000 eggs per gram or more.

“If you find you have egg counts running into the thousands, then you can then do further tests by sending off faecal samples to the laboratory for a Peanut Stain test. Post Mortems on dead sheep are also really valuable to confirm Haemonchus on farm.”

Adult sheep are also susceptible as there is little effective immunity to Haemonchus. This makes quarantining any sheep moving onto the farm vitally important.

- Treatment

When it comes to treatment there are a range of options for farmers, says vet Dr Dave Armstrong from Zoetis, but he advises seeking advice first.

"If you are only treating for Haemonchus, then the treatment option may be different compared to if you are treating a mixed worm burden. Resistance to some worm treatments for Haemonchus have been reported in other parts of the world, including Europe. Because of its destructive nature, it is important we use wormers effectively and prevent the build-up of resistance.

“This includes not only using the correct product but making sure the right dose is given for each animal, making sure dosing guns are properly calibrated, quarantining any incoming stock, taking regular faecal egg counts to monitor worm burdens and having a strategic grazing management in place and conducting post-drench faecal egg count tests.”