Limping does not necessarily equate to Mareks. There could be many causes, starting with an injury of some sort to her foot. Mareks does not usually onset with limping; leg or wing paralysis is a much more common symptom, although there can be other causes for those, too.
Virtually all chickens that are not in laboratory isolation conditions carry Mareks. From the Meck Veterinary Manual: "Marek's disease is one of the most ubiquitous avian infections; it is identified in chicken flocks worldwide. Every flock, except for those maintained under strict pathogen-free conditions, may be presumed to be infected. Although clinical disease is not always apparent in infected flocks, a subclinical decrease in growth rate and egg production may be economically important."
There are some strains of Mareks that are fairly virulent, but most are not, so chances are that even if the bird has/had Mareks, the rest of your flock will be fine..
I always thought she was blue all along because she has no black. Her base colour (is the blue the base?) is the same colour as her mother - which is blue. However, I kept a partridge male that has black where she has blue. I plan to breed those together.
X 100 !!!!!!!!!!!!! Pam
