My chickens have been dropping like flies for the past few months. We had them for over 10 years with no problems- only lost on hen in that time to a raccoon and the other hens all lived past 10 years old. Anyway, we found that the culprit is Mareks. A warning to new chicken owners- buy vaccinated chicks that have been properly quarantined. We had to put down our pets and will try to start over next year with vaccinated chicks. Mareks is everywhere and even if you don't have it, and rodent or bird can bring it to your property. Beware.