Treating liver fluke

The threat of liver fluke varies from year to year, from farm to farm, and even from field to field. Therefore, the need to risk-assess and test for liver fluke before treatment in individual flocks is really important - go to Fluke detection, treatment and control for more information.

If, having gone through the steps of risk assessment and testing, the right decision is to treat sheep with a flukicide, the decision on which products to use can be daunting.

Top tips

  • When treating sheep, be aware of the flukicides available for different ages of fluke (see table).
  • Resistance to triclabendazole (TCBZ) is not uncommon and we need to avoid overuse of these medicines if we are to protect their long-term efficacy.
  • Remember no flukicides have any persistent activity. Moving animals away from the high-risk area (for example, housing post-treatment) is the only way to avoid reinfection.

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Warning about rafoxanide

With such a limited number of different flukicides available and reports of resistance to triclabendazole (TCBZ) increasing every year, choice of treatment is extremely important. Choice should be made on active ingredient, as products with different trade names are not fundamentally different to each other just because they are branded differently. For example, Fasinex and Triclacert both have triclabendazole as the active ingredient, while Flukiver and Solental are closantel. See the SCOPS ‘Know Your Anthelmintics Groups’ guide for more information.

There are also specific concerns with two veterinary medicines that are not currently authorised in the UK but have been imported from the Republic of Ireland under a Special Import Certificate from the Veterinary Medicines Directorate for use on some UK farms. These veterinary medicines both contain the active substance rafoxanide. SCOPS and COWS are aware there is some confusion around rafoxanide, especially with respect to using it as an alternative to closantel on farms where triclabendazole resistance is proven.

  • Rafoxanide is not a new flukicide. It has been available in some countries, for example Australia and the Republic of Ireland, since the 1980s.
  • Rafoxanide is a salicylanilide anthelmintic. Other compounds in this class include closantel and oxyclozanide. Hence rafoxanide is not a different class of flukicide to closantel. Rafoxanide and closantel are similar in chemical structure and mode of action. There is evidence of cross-resistance between rafoxanide and closantel from both field and laboratory studies (Boray and de Bono, 1989).
  • Relationship with closantel. There is no evidence to suggest using closantel and rafoxanide interchangeably/on a rotational basis will successfully reduce the selection pressure for resistance to closantel. Indeed, there is a serious risk that such use of rafoxanide will hasten the development of resistance to closantel. Hence rafoxanide is not considered an appropriate alternative to closantel.
  • Relationship with oxyclozanide. Fluke isolates resistant to rafoxanide and closantel show no side resistance to oxyclozanide (another member of the salicylanilide group). It is thought this is because of the different pharmacokinetics of oxyclozanide and that it is only effective against adult fluke.

Treatment recommendations

SCOPS and COWS recommend that veterinary medicines are used to target the predominant age of fluke likely to be present in a group of animals at a particular time (e.g. immature fluke in autumn, adult fluke in spring and summer). As stated above, it is also strongly advised that appropriate diagnostic tests are used before each treatment is given.

Closantel is a useful drug to control immature fluke in autumn, but alternatives such as nitroxynil, albendazole, oxyclozanide or clorsulon can be used at other times of year when adult fluke predominate.