Is ivermectin used as a preventative or to cure an outbreak? I will be buying the pour on kind for my silkies. I have think I have lice going around. I have dusted the heck out of them but want to make sure I the parasites hard. Does tractor supply have ivermectin? What is it labeled as? I hear its just for cow and pigs and not necessarily chickens. Has anyone used ivermectin? Any comments or tips about it? Also, does can sevin dust cure an outbreak?