Hi, we've had 8 backyard chickens, this is our third summer. Over the last 6 months or so our dogs have been getting fleas. We've used the traditional spot stuff on them, which usually gets rid of all the fleas, but they are not going away this time. We have not seen a single flea on the chickens. Anyone know if the chickens can be the source of the fleas, and if so, what can be done about it? Thanks!! The dogs are miserable.