My dogs work fox, but I always pull the dogs and let the fox bolt. Only one of my farms has "free range" chickens, and these chickens are in an outdoor coop that is well fenced provided the farmer or my dogs do not knock the groundhogs off if they burrow underneath the fence line.
As I have noted in the past, Red Fox Are a Weapons of Mouse Destruction, and it is white-footed deer mice that are the true reservoir of the the Borrelia microbe that is passed on to ticks, and possibly, to dogs and humans, and which is the cause of Lyme disease in people and dogs.
Conversely, a rise in coyote populations actually exacerbates Lyme, at least a wee bit, because they compete with, and push out red fox, which eat far more mice than coyotes do.
Now a European scientist has spent time documenting two things we have always known: red fox eat a hell of a lot of mice, and those mice carry Lyme. What's interesting is that something more was actually learned. As The New York Times reports:
Interestingly, the predator activity in Dr. Hofmeester’s plots did not decrease the density of the mouse population itself, as some ecologists had theorized it might. Instead, the lower rates of infected ticks, Dr. Hofmeester suggested in the paper, published in Proceedings of the Royal Society B, may be the result of small mammals curtailing their own movement when predators are around.
“This is the first paper to empirically show that predators are good for your health with respect to tick-borne pathogens,” said Dr. Taal Levi, an ecologist at Oregon State University who was not involved in the study. “We’ve had the theory but this kind of field work is really hard and takes years.”