A Brief Note About Marek’s Disease- Chickens Part 2

Marek’s Disease, which we will go into in more depth in the next course, is an incurable, contagious disease caused by a herpesvirus.  It is spread from bird to bird through molted feathers and dander from infected birds, which is then inhaled by other birds. Marek’s can cause a host a serious symptoms including full or partial paralysis.  

A Marek’s diagnosis can only be confirmed on a post mortem exam.  The blood test available is not helpful because it tests for antibodies meaning a bird will test positive if they have been vaccinated (and most chickens from industrial settings are vaccinated); the test cannot differentiate between someone who has been vaccinated for Marek’s and who actually has the disease. Veterinarians make presumptive diagnosis based on the clinical signs present.  Because it can cause such a wide range of symptoms, it is not uncommon for a veterinarian to assume a bird has Marek’s and to immediately recommend euthanasia.  In these instances, please ask about other potential causes of the bird’s illness and discuss diagnostic or treatment options to try to confirm or treat those conditions.  We’ve heard horror stories from sanctuaries who euthanized a sick bird because the veterinarian was convinced the bird had Marek’s, only to find on a post-mortem examination that there was a different, sometimes treatable cause.  Always consider exhausting other options before moving ahead with euthanasia.

Even in the event that a bird truly does have Marek’s, the presence of the disease in and of itself should not be death sentence.  There are varying degrees of severity, and anecdotally, some sanctuaries have seen birds with severe Marek’s symptoms recover (though many of these birds had relapses later on), and therefore, they choose to provide supportive care including finding ways to get the bird up off their legs during these times.  The individual’s quality of life should be the main factor when considering euthanasia, not the concern of Marek’s alone.