I have to agree with dawg53, I had chickens for 3 yrs never a problem with any thing. Then WHAM, lost some chickens before we discovered the problem, cocci and worms. Vet check confirmed what the problem was, chokes are doing well now and I will continue to treat yearly now. ... one of the meds we used was the fenbendazole recommended by the vet. you need to remember most wormers do not kill ALL worms so you kneed to know what you are treating for,so you get the right med.