Infectious bronchitis is caused by a corona virus which leads to damage of the upper respiratory tract and oviducts. The virus can also infect the intestine and kidneys. There are many different strains and the virus works with other pathogens to cause disease in the bird. In layers, infectious bronchitis can cause:
Aetiology
The disease is caused by a virus which often combines with other viruses, mycoplasma and bacteria to cause a chronic respiratory infection. The other pathogens can be TRT, MG and E coli.
Signs
The IB virus damages the cells lining the wind pipe which act to prevent dust, bacteria and other foreign material entering the lungs. There are similar cells lining the oviduct and these cells can also be affected leading to abnormal shell changes. The damage to the protective cell lining the windpipe allows bacteria and other viruses to enter the lungs and air sacs. The bird does not have a diaphragm as we do and also has very thin walled air sacs throughout the abdomen and thorax. These air sacs will penetrate into bones. Their function is to fill with fresh high oxygen air when the bird breathes in. When the bird breathes out the fresh air is passed through the lungs allowing the bird to take up oxygen into the blood on breathing in and also breathing out. This adaptation is needed to allow for rapid muscle action required in flight. The problem is however, if infection enters the wind pipe then it has rapid access to the air sacs and easily can cross into the blood stream. This in turn leads to a condition called peritonitis. A bacterial peritonitis will often cause death.
The infection in the oviduct will also affect the bird’s natural defences and peritonitis due to infection tracking up the oviduct is a common sequelae to IB infection.
Control
You cannot treat IB with antibiotics and the best control is by vaccination. The type of vaccine used depends on the type of IB involved and close consultation with your vet is essential.
Treatment of the secondary infections might be advised by your vet.