In general, if the fleas are on our dog, they might jump on your chicken, but they will not be able to breed on your chicken.
But, your chicken could get a kind of flea that lives and breeds on chickens, either from other chickens (or used nest boxes or perches etc.) or from wild birds.
Many people like to sprinkle DE powder, food grade, around the coop, run, and on perches, since that helps to greatly reduce all sorts of parasites.
Also, wood ash (from good clean wood, no pressure treated lumber or other potential toxic stuff) in a pile is a great dust bath and is also toxic to some pests.
You should pick up your hens every so often and look under their feathers and around their vent and see if you see any bugs. Even if the bugs are hiding (some nasty parasites live in the wood of the coop, and crawl onto the chicken to eat, then go back and hide in the wood) they will leave some sign of their presence. Usually there will be tiny black freckles over the chicken's skin which are tiny bites and then the scabs.