Quail bronchitis is caused by avian adenovirus (Aviadenovirus) group 1 serotype 1. Affecting wild and captive-reared quail, it is highly contagious and, on premises with poor biosecurity measures, often fatal. It is characterized by rapid onset, as well as high morbidity and mortality rates. Affected birds exhibit ocular and nasal discharge with respiratory distress. Diagnosis is based on clinical signs and on gross and microscopic lesions and is confirmed by virus isolation or detection of the virus using immunological or molecular techniques. There is no specific treatment.
Quail bronchitis is a naturally occurring, highly contagious, often fatal respiratory disease primarily of bobwhite quail < 2 months old in the wild and in captivity, but it also occurs in other quail species.
This worldwide disease can have major economic impact on game bird breeders. It can have catastrophic consequences on farms where quail are raised in pens, particularly when quail of various ages are maintained on the same premises and appropriate biosecurity measures are not followed.
Quail bronchitis is characterized by rapid onset and high morbidity and mortality rates. The quail bronchitis virus is infectious for other avian species, including poultry; however, infection is generally subclinical. Other avian species, particularly chickens, can be carriers.
Etiology and Epidemiology of Quail Bronchitis
The virus that causes quail bronchitis is classified as a group I serotype 1 avian adenovirus in fowl adenovirus species A that can be readily isolated from the respiratory tract of acutely affected birds. It contains a DNA genome, is nonenveloped, and ranges in diameter from 69 to 75 nm.
Quail bronchitis virus is easily isolated from fecal samples, as well as from tissue samples of the trachea, air sacs, or lungs; intestine; liver; and occasionally the bursa of Fabricius (cloacal bursa).
Quail bronchitis is highly contagious and spreads rapidly through multiple-age units. Although not experimentally documented, transmission of the disease is likely via aerosol and fecal-oral routes.
Serological evidence indicates that other gallinaceous birds are susceptible to infection by quail bronchitis virus but do not develop clinical signs.
Clinical Findings of Quail Bronchitis
Typically, the first sign of quail bronchitis in a flock is a sudden increase in deaths. Feed consumption decreases, and sick birds have ruffled feathers and dropped wings and might huddle under brooders.
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 can be completely filled with mucus), and GI signs can occur.
The mortality rate associated with quail bronchitis might reach 80% in birds < 2 weeks old (1); however, it is usually < 25% in birds > 4 weeks old.
Lesions of Quail Bronchitis
The gross lesions of quail bronchitis involve primarily the respiratory tract but can also involve the GI tract. Lesions might include tracheitis, airsacculitis, hepatitis, and gaseous distention of the intestines. Necropsy of infected birds might reveal any of the following common lesions:
nasal and ocular discharge
thickening of the tracheal mucosa, with distention by mucous, necrotic, and sometimes hemorrhagic exudate
cloudy-appearing anterior air sacs containing exudate similar to that found in the trachea
congestion of the lungs, with consolidated areas around the bronchial hilus
multiple pale, pinpoint (< 3 mm diameter) foci of necrosis in the liver
mottling and enlargement of the spleen
Histopathological lesions of quail bronchitis include necrotizing tracheitis characterized by epithelial deciliation, cell swelling, desquamation of necrotic epithelium, basophilic intranuclear viral inclusion bodies, and infiltration of inflammatory cells. In the lungs, there is necrotizing, proliferative bronchitis with similar lesions as in the trachea. Lesions in the liver and spleen include multifocal areas of necrosis, with infiltration by inflammatory cells and inclusion bodies.
Intranuclear viral inclusion bodies are often evident in hepatocytes adjacent to areas of necrosis. Occasionally, microscopic areas of lymphoid necrosis associated with inflammatory infiltrates, diffuse lymphoid depletion, and follicular atrophy occur in the bursa of Fabricius.
Diagnosis of Quail Bronchitis
Sudden increase in morbidity and mortality rates in a flock
Clinical signs
Isolation of virus
Diagnosis of quail bronchitis is based on a history of sudden high morbidity and mortality rates in a flock, along with clinical signs of respiratory distress associated with characteristic lesions in the respiratory and GI tracts. The diagnosis is confirmed by isolation of avian adenovirus (Aviadenovirus) group 1 serotype 1 or by demonstration of the virus in infected tissues using immunological or molecular techniques.
Treatment and Control of Quail Bronchitis
No treatment
Biosecurity measures
There is no specific treatment for quail bronchitis. If stringent biosecurity measures are implemented, the disease is often self-limiting. Experimental vaccines have proved ineffective at preventing the disease.
Although there is no specific treatment, increasing the brooder temperature by 1.5–3°C (3–5°F), preventing overcrowding and avoiding contact between older and younger birds and other avian species are useful measures against quail bronchitis, as are strict isolation and sanitation of personnel and equipment.
Immunity to quail bronchitis lasts a long time, possibly for life, and recovered birds can be retained as breeders. New birds should not be introduced to the premises until after a 30-day quarantine.
Pearls & Pitfalls
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Avian adenoviruses have not been demonstrated to be zoonotic.
For More Information
Fitzgerald SD, Rautenschlein S, Mahsoub HM, Pierson FW, Reed WM, Jack SW. Adenovirus infections. In: Swayne DE, ed. Boulianne M, Logue CM, McDougald LR, Nair V, Suarez V, associate eds. Diseases of Poultry. 14th ed. Wiley Blackwell: 2020:321-363.
References
DuBose RT, Grumbles LC, Flowers AI. The isolation of a nonbacterial agent from quail with a respiratory disease. Poult Sci. 1958;37(3):654-658. doi:10.3382/ps.0370654
