Farmers warned care needed when using triclabendazole alternatives
Adobe Stock Animal health leaders concerned about anthelmintics resistance are urging farmers reaching for alternatives to an established drug to research the active ingredients in liver fluke products.
Resistance to triclabendazole, the only active to kill all ages of fluke, means more flockmasters are reaching for the antiparasitic drug closantel, which two industry-leading groups warn must be done with care.
The Sustainable Control of Parasites in Sheep (Scops) and Control of Worms Sustainably (Cows) groups have warned that closantel currently has no available alternative.
It typically requires two treatments, six to seven weeks apart.
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Concerns are growing that farmers are mistakenly using rafoxanide in the belief they are protecting closantel.
However, both closantel and rafoxanide have similar structures (salicylanilide molcules) and similar modes of action.
Cross-resistance
Lesley Stubbings, independent consultant and Scops spokesperson, said: “Experts working with Scops and Cows agree there is evidence of cross-resistance between rafoxanide and closantel from both field and laboratory studies, and no evidence to suggest using them interchangeably will reduce the selection pressure for resistance to closantel.”
Describing the flukicide options available to farmers, Lesley said, in essence, there are three flukicide groups:
- Triclabendazole This is the only treatment that kills immature liver fluke, from two days in sheep and two weeks in cattle.
- Closantel and nitroxynil These kill liver fluke as young as five days of age, but nitroxinil can only be used in the UK if imported by vets under a Veterinary Medicines Directive special import certificate.
- Albendazole and oxyclozanide These drugs only kill adult fluke. Species-specific products are also available – clursulon (cattle) and rafoxanide (sheep).
Lesley added: “The key to choosing the right product is understanding the differences between the actives available and the age of liver fluke parasites that need to be killed.
“This will not only reduce the risk of repeated/overuse of the same flukicide, but also ensure the best outcome for the sheep or cattle treated.”