These are a common problem during warm weather. Adult female fleas bite foxes to obtain blood. They then lay eggs in cracks, etc. around pens and next boxes. These eggs hatch to small larvae which soon form into pupae. Any vibration will stimulate the new crop of fleas to hatch. The entire cycle takes about 14 days.
90% of fleas live in the environment and not on the host. Therefore, environmental treatment is as important as treating the animal. Fleas can be controlled by good sanitation and treatment. Other flea hosts on the ranch are often overlooked during treatment. These may include dogs, cats, rabbits, squirrels, raccoons, etc. Bear in mind that the majority of fleas are in the environment and it should be treated equal or more aggressively than the fox itself.
Treatment with pyrithrins will kill fleas. Pyrithrin dust may be used in the bedding and nest boxes. Dusting should be repeated in two weeks to kill any fleas which have recently hatched and break the life cycle. 5% malathione can also be used in the same manner as pyrithrin, but not two weeks prior to or four weeks after whelping.
Fleas can spread disease, cause anemia and irritation in large numbers, so should be controlled.