Finland was free of IB for nearly three decades, until the disease was found at one egg-laying hen farm and in one backyard chicken in 2011. IB has also been found in flocks of broiler breeder hens and on broiler farms.

It is possible that the strains of IB virus (IBV) have spread to Finland from our neighbouring countries through illegal import of live poultry for non-commercial use. Another possibility is that a live vaccine virus is reverting into a more virulent form capable of causing disease.

Infectious bronchitis in chickens is caused by the highly contagious coronavirus. In addition to respiratory tract infection, the clinical signs of IB in chickens include infertility, drop in egg production, poor eggshell quality and kidney failure, but the disease is not generally fatal.

Vaccinations are commonly used to combat infectious bronchitis. Vaccines have been developed against the most common strains of IBV and are used extensively worldwide.

“There is a possibility that a live vaccine virus has reverted into a more virulent form capable of causing disease. Further studies will be required to confirm this,” says Senior Researcher, Ph.D. Anita Huovilainen from Evira's Veterinary Virology Research Unit.

Since the summer of 2011, an inactivated IB vaccine has been used to some extent in Finland.

Infectious Bronchitis Found Worldwide

There are dozens of known strains of the IB virus, with varying signs and effects. The disease is extremely common, both in Europe and worldwide.

“The strain of IBV found in Finland in 2011 was identified through more detailed analysis as genotype QX, which has been very common in Europe in recent years. The IB strain diagnosed in one backyard chicken in 2011 was confirmed as the same QX strain that was found at the egg-laying hen farm that same year,” says Ms Huovilainen.

However, the strains were not identical, which suggests that they originated from different sources. Further analyses were conducted on blood samples collected from flocks of backyard chickens, and antibodies to IBV were commonly found in the samples. The presence of antibodies is a sign of the birds having had the disease at some point in their life.

After 2011, signs of respiratory tract infection as well as diarrhoea and drop in egg production have also been observed among flocks of broiler breeder hens and in broiler farms.

“IB has spread among poultry, but studies have not helped identify where the different strains of IB virus found in Finland originate,” says Ms Huovilainen.

Further Reading

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