Triclabendazole resistance – how to cope with it

Effective management of liver fluke in sheep can be based on a ‘4 Point Plan’:

1. Effective treatment of animals at risk – using the right product at the right time. However, if the farm has fluke that are resistant to triclabendazole, there is no longer an effective treatment for the youngest stages of fluke (up to 5 weeks) in the animal. This means that for effective fluke control, the focus needs to be on the other 3 points of the plan:
2. Pasture protection – using an effective adulticide treatment in early summer to minimise pasture contamination with fluke eggs going into autumn
3. Grazing management –fencing off wet or boggy areas, which offer a perfect habitat for snails, so are high risk for metacercaria; planned use of forage crops and/or housing to keep animals off high risk areas at high risk times of year
4. Pasture management – fix leaky troughs and maintain effective drainage to minimise snail habitats and reduce snail numbers to reduce the number of infective stages (metaceracria) released onto pasture

Where there is confirmed resistance to triclabendazole, careful use of all the remaining actives will be necessary. Just switching to closantel (the next on the list for ability to kill immature fluke) will lead to overuse of this active and will then generate resistance to closantel too. So far there have been no confirmed cases of resistance to closantel in the UK. However in other parts of the world there is already significant levels of closantel resistance. If closantel is overused here in the UK, it is not a case of if resistance occurs, but when.