Liver fluke is shaping up to be a significant challenge this winter. With a very limited number of different flukicides available and reports of resistance to triclabendazole (TCBZ) increasing every year, choice of treatment is extremely important. SCOPS and COWS are committed to try to provide clear advice on the options available.
There has been confusion with respect to two veterinary medicines that are not currently authorised in the UK, but which have been imported from Ireland by UK veterinary surgeons, 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 that there is some confusion around rafoxanide especially with respect to using it as an alternative to closantel on farms where triclabendazole resistance is proven. This paper aims to clarify the situation.
Rafoxanide is not a new flukicide. It has been available in some countries, for example Australia and the ROI 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.
This is extremely important because it means there is no evidence to suggest that 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.
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). We strongly advise using appropriate diagnostic tests 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. See the Tables below:
More details: Liver Fluke Treatment options in sheep
More details in the AHDB Parasite Control Guide that AMTRA has sent to all farm SQPs.