Marek’s Disease Virus (MDV) causes tumorsand immunosuppression in chickens, and occasionally turkeys and quail. Infected flocks generally show clinical signs between six and 30 weeks of age; however, the disease can affect older birds as well. Not all infected birds show symptoms but will continue to shed the virus for life.

Omphalitis is a fairly common infection, also known as “mushy chick disease” or “yolk sac infection,” and it occurs in the first few days of a bird’s life. It is seen most commonly in artificially hatched eggs and is associated with contaminated eggs or incubators.