Symptoms: slow decline. Chickens get slowly weaker and weaker. Some limping which throws me off. Sometimes messy drainage on anal feathers. The rooster got very pale in the wattles and legs at the end but the hens seemed to retain their color. They all rally when I do something for them - give them liver or a warm soak - and then get rapidly ill acting again. There didn't seem to be much of a response to spraying their coop a couple of times. I want to have a plan in case another hen starts to decline. A chicken dies, there is about a two week delay and then another one gets ill. The ducks seem unaffected. Nearly all of those chickens were pretty old, 5 + years. I have had chickens for 15 or 20 years with no problems except varmints in the early years. I thought the first was a fluke. The second I thought was egg bound and did respond to a warm water, epsom salts bath and then relapsed. My beloved rooster then perished though, by now I suspected lice or something. I started spraying the coop but I was too late, that was not the problem or I didn't do enough. The chickens took varying times to die. About a month, though. The rooster went fast but the younger 5 year old hen hung on for about a month. We had an unusually hard winter with multiple very hard freezes in our Central Texas area.