for loosing one. Yup, they can suck the life right out of a host.
Sevin dust (5%) is helpful. Mites need to have the coop treated as they do not live on the chicken (they hid during the day in the cracks in the coop, come out at night and feed). Remember to retreat in 10 days and then again in 10 days to kill all the bugs who have hatched after the first kill.