...and isi showing neurological symptoms like limping and leg paralysis, and tremors in the legs and has had these symptoms for a few weeks now (3-4 wks), wouldn't my other chickens be getting symptoms also? I treated her for mites and lice the other day, which she had, hoping she would improve, and she hasn't yet. None of my other chickens have symptoms. Is this possible? CAn a chicken be exposed to it and not contract it? I have pre-laying pullets and cockerels, plus birds that are 1 and 2 yrs old. And wouldn't she have declined a lot quicker? Does marek's always kill them?