If Mareks was a problem, it takes 3 weeks or more after exposure to a carrier at the minimum for symptoms of Mareks to appear. Mareks can be diagnosed with a couple of different ways. The most common is to get a necropsy through your state poultry vet where they can do testing for Mareks. The other way would be to send of for a kit, and collect blood to do a pcr test for Mareks through RAL here:
http://www.vetdna.com/application/forms/aviansubmittalform.pdf
http://www.vetdna.com/application/forms/aviansubmittalform.pdf
