I don't agree that, on the basis of the picture, this is a fox with some kind of disease. You've seen it better, but it does not have upright ears, it is short-haired (mange? it looks shiny to me) and it doesn't have a long tail. I think it is more likely a dog or a hybrid of some kind. I agree with the previous poster; contact your local wildlife rescue or humane society, and keep your chickens protected (and your children, of course, though they would have to cuddle up with it to get mange, if it even has that). It's eating your chickens, yeah! they're yummy, but thats just doin' what comes naturally. I love it that you took a picture and didn't immediately resort to the all-out assault.