Being a rescue we do have to treat our animals on a regular basis. I consulted with the vets and got Ivermectin by the bottle and details of doses for diferent animals. I did not do this regularly before we had rescues only the cat. Would I do it now without the rescues....probably I think, done properly there are few side efects or risks and very litle stress caused to the animal. fleas do spread Miximatosis and mites and lice can cause any amout of bother.