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  • Writer's pictureACT Wessex Animal Health

Haemonchus Contortus

What is it?

Haemonchus contortus, also known as the "barber's pole" worm, is now widespread in the UK. The adult worm feeds on blood and is responsible for causing anaemia and death in both adult and young sheep. When ewes are affected, even those not demonstrating obvious clinical signs can show decreases in productivity and a reduction in milk yield. Under fed lambs may not grow as well, and as they are wean themselves onto grazing, they will acquire heavy burdens of their own.

The incidence of haemonchosis, as well as its geographical spread, has increased recently in the UK; most likely, this is as a result of climate change. Adult haemonchus worms are highly prolific egg layers, meaning outbreaks can occur very quickly.

Clinical signs

• Anaemia

• Submandibular oedema (bottle jaw)

• Increased heart and respiratory rates

• Lethargy, weakness, rapid loss of condition

• Diarrhoea is NOT a feature - diarrhoea may indicate additional worm species burdens

• Particular issue in growing lambs

• Adult sheep do not develop immunity


Most wormers will claim efficacy against Haemonchus but to avoid overuse of any one particular anthelmintic group it is worth considering a Closantel based drench, a narrow spectrum parasiticide which is effective against H. contortus as well as liver fluke. It is also active against benzimidazole resistant strains of H. contortus.

Closantel does not require metabolism by the liver to become active (unlike triclabendazole which is rendered less useful in the face of liver damage): it is absorbed unchanged into the bloodstream, and has limited distribution into other tissues, which means that it specifically targets those parasites which feed on blood, namely liver fluke and Haemonchus contortus. It is also eliminated relatively slowly from the sheep’s bloodstream.

  • Effective treatment against inhibited, L4 and adult stages of the "barber's pole" worm (Haemonchus contortus) and the sheep nasal bot fly (Oestrus ovis).

  • Kills fluke from 5 weeks to adult.

  • Kills triclabendazole-resistant fluke.

For help and advice on dealing with Haemonchus please speak to one of our Amtra qualified SQPs on 01425 474455

Haemonchus contortus, also known as the "barber's pole" worm

Information Kindly Supplied by Norbrook



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