Quail bronchitis is a naturally occurring, highly contagious, often fatal respiratory disease of bobwhite quail < 2 months old) in the wild and in captivity. The worldwide disease can be of major economic impact to gamebird breeders. It can have catastrophic consequences on farms where quail are pen-raised, particularly when quail of various ages are maintained on the same premises and appropriate biosecurity measures are not followed.
The causative agent, quail bronchitis virus, is a Group I serotype 1 avian adenovirus that can be readily isolated from the respiratory tract of acutely affected birds. The virus is also easily isolated from fecal samples as well as tissue samples from the intestine, liver, and occasionally the bursa of Fabricius. It is highly contagious and spreads rapidly through multiple-age units. Other avian species, particularly chickens, may be carriers.
Clinical signs of quail bronchitis include respiratory distress, coughing, sneezing, rales, and nasal or ocular discharge. Loose, watery feces are common in some acutely affected older birds. Conjunctivitis, mild to severe tracheitis (the trachea may be completely filled with mucus), airsacculitis, hepatitis, and gaseous distention of the intestines may occur. Mortality rate may reach 100% in birds <2 weeks old but is usually <25% in birds >4 weeks old. At necropsy, multiple pale, pinpoint (< 3 mm diameter) foci of necrosis in the liver and mottling and enlargement of the spleen are common lesions. Occasionally, necrosis of the bursa of Fabricius occurs.
The disease is often self-limiting if stringent biosecurity measures are implemented. Experimental vaccines have proven ineffective in preventing the disease. There is no specific treatment; however, increasing the brooder temperature by 3°–5°F (1.5°–3°C), preventing “piling up,” and avoiding contact between older and younger birds and other avian species are useful measures, as are strict isolation and sanitation of personnel and equipment. Immunity is long lasting, possibly for life, and recovered birds can be retained as breeders. New birds should not be introduced to premises without a 30-day quarantine.
Avian adenoviruses have not been demonstrated to be zoonotic.