S1 gene based phylogeny of Israel variant-2 infectious bronchitis virus isolated in Turkey in a five year period.

Infectious bronchitis (IB) is an important disease that causes severe economic loses in the poultry industry worldwide. Furthermore, the spread of new variants poses a challenge for diagnosis and control of the disease. This study investigated the situation of infectious bronchitis virus (IBV), specifically the Israel variant-2 (IS var-2) also known as GI-23 genotype, in Turkey. Between 2014 and 2019, 214 flocks vaccinated against H120 from Marmara, Western Black Sea, and Inner Anatolia were examined, with 127 (59.3%) flocks testing positive for IBV, of which 92 (72.4%) were positive for IS var-2. Of the latter samples, 60 were randomly selected and subjected to full S1 gene sequencing. The analysis indicated that the field strain in Turkey was located on the same branch as the GI-23 genotype, which is one of the most frequently observed wild-type cluster found in the Middle East. The DNA similarities between the GI-23 isolates from 2014 to 2019 were 99%. In conclusion, the IS var-2 genotype has been circulating in broiler flocks in Turkey. It is recommended that establishing the vaccine strategy it should be considered the current circulating strains for the prevention and control of the disease among poultry.