Occurrence: Increasingly common worldwide especially in areas with high altitude or colder environment where gas brooders are needed extensively.
Species affected: Fast growing broilers and turkeys.
Age affected: Especially young, fast growing birds.
Causes: Non-contagious. Influenced by genetics, breeding, nutrition, growth rate, ambient temperature and oxygen content of the air.
Effects: Water-belly, abdominal distension, reluctance to move, dyspenic and cyanotic lesions seen. Affected birds are smaller than normal, and listless with ruffled feathers. Mortality ranges from 0.5-2.0% of the flock.