An acute, transmissible, infectious disease associated with high MORTALITY and MORBIDITY in young turkeys (poults). It is characterized by DIARRHEA; ANOREXIA; growth depression, and immune dysfunction. The cause is unknown but astroviruses (AVASTROVIRUS) and coronaviruses (CORONAVIRUS, TURKEY) have been isolated from diseased poults and are thought to cause the enteritis and increased susceptibility to bacterial infections. [from MeSH]