Infectious bronchitis may have returned to Finland’s poultry flocks through spread from neighboring countries or via a live vaccine virus reverting to a more virulent form capable of causing disease.
The disease was absent from Finland for 30 years, however it was detected at a layer farm in 2011 and subsequently in broiler breeder hens and on broiler farms prompting the Finnish Food Safety Agency Evira and the University of Helsinki Faculty of Veterinary Medicine to look study its re-emergence.
“There is the 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,” said senior researcher Anita Houvilainen from Evira’s Veterinary Virology Unit.
She continued that the strain of infectious brochitis virus (IBV) found in Finland in 2011 was identified as genotype QX, which has been common in Europe in recent years. The IB strain that was diagnosed in one backyard chicken in 2011 was confirmed as the same QX strain that was found at the egg farm the same year.
However, the strains were not identical, suggesting 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 the disease at some stage in their lives.
After 2011, signs of respiratory tract infection, as well as diarrhea and a drop in egg production have also been observed among flocks of broiler breeder hens and at broiler farms.
“IB has spread among poultry, but studies have not helped identify where the different strains of IB virus found in Finland originate,” added Houvilainen.