Infectious Bronchitis (IB) is an acute, highly contagious disease of chicken, characterised by coughing, sneezing and rales (rattling). The disease is caused by a coronavirus that infects chicken only. Due to the virus’ affinity to change its antigenicity, there are several different antigen types.

Infectious Bronchitis is considered the most contagious poultry disease. When it occurs, all susceptible birds on the premises become infected, regardless of sanitary or quarantine precautions. The disease can spread through the air and can "jump" considerable distances during an active outbreak. It can also be spread by mechanical means such as on clothing, poultry crates and equipment. The disease is not egg transmitted and the virus will survive for probably no more than one week in the house when poultry is not present. It is easily destroyed by heat and ordinary disinfectants.

Deformed shell
Thin shell

The clinical disease is pronounced in respiratory symptoms due to an inflammation of the bronchial mucous membrane. Symptoms are difficult breathing, gasping, sneezing and rales. Some birds may have a slight watery nasal discharge. The disease never causes nervous symptoms. It prevails for ten to fourteen days in a flock. In chickens under three weeks of age, mortality may be as high as thirty or forty percent. The disease does not cause a significant mortality in birds over five weeks of age. Feed consumption decreases sharply and growth is retarded.

In layers the disease causes a dramatic drop of egg production, with thin shell and deformed eggs. Brown eggs are often discoloured. Mortality only appears in very young chicks and can be increased by additional infections of MG or E. coli. An infection in the first weeks of life can cause permanent damage on the reproductive tract and may lead to “false layers”.

Infectious Bronchitis is difficult to differentiate from many of the other respiratory diseases. For this reason, a definite diagnosis usually requires a laboratory analysis.

IB is highly contagious and does not always respect sanitary barriers. In the prevention of the disease, live vaccines containing the prototype strain “Massachusetts” are used worldwide. Vaccinations via the drinking water or by spray are the most effective methods of live IB vaccine application. Live IB vaccines should be administered repeatedly during rearing, but can also be applied during production as a booster, in order to prevent production losses.

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