Tripp16, I would really suggest with the next death that you send for necropsy. ALternatively, you could look into the blood test at texas....a vet should be able to help with that. THe thing is, knowing for sure, would help you move forward and make decisions.
Best if you can figure out the detailsin advance of how to handle the dead chicken and where to send it, etc so it can be done.
Here is info on the blood test :
One PCR test available at University of Texas requires chicken blood collected in EDTA (noncoagulated) to be tested for Marek's disease virus nuclei acid. this test is approx. $30 per sample and would be conducted on birds that are still alive.
A second test, available at University of Georgia, is conducted on tissue or blood. I called the lab and the technician believes they can test brain that has been previously fixed in preservative, but she will have to confirm. This test is approximately $110.
Please keep in mind that both of these tests only indicate that birds have been exposed to the MD virus and do not prove that MD is the primary disease. Many birds can test positive for MD with such tests because the virus is ubiquitous, but many exposed birds do not develop clinical signs or lesions because they have been vaccinated.
I think you would need a vet to properly collect the blood and to be in contact with the univ of texas but any vet should be willing to help with that.
It is a hard blow. I found out about mareks via necropsy in Oct and it hit me pretty hard. I have learned more now and feel a bit better, although my future plans went up in smoke, too.