How do I get rid of flukes?

I believe I have flukes in my 40. They showed up shortly after adding a new fish. Question is has anyone had luck getting rid of them? I have done two doses of prazipro with no luck. It seemed to keep them from getting out of control but I still have them. I'm afraid if I keep dosing it they will just become immune to it. So what else should I do? I know I could set up a small tank for the fish and treat them. But with what as the prazipro isn't working. Please help!!!!