local agricultural vet, or even nearby farmers. If you have fields close to burns/rivers, anything that is likely to flood at some point during the year you are likely to have fluke. However it is not the end of the world if you have it, I dose twice yearly with Fasinex and that's it. According to my vet fluke does not get resistant to Fasinex, so no swaps/changing to different stuff necessary (just as well that the bottles - very large - last for a few years, as the one I recently bought was over 50quid but is useable until 2014!!!!)