Detection of different genotypes of infectious bronchitis virus and of infectious bursal disease virus in European broilers during an epidemiological study in 2013 and the consequences for the diagnostic approach.

To gather recent data regarding the infectious bronchitis (IB) and infectious bursal disease (IBD) situation in Europe, a large-scale field epidemiological survey using diagnostic samples has been implemented in 2013 for about six months in several European countries: France, Germany, Greece, Italy, the Netherlands, Poland, Portugal, the Republic of Ireland, Spain and the UK. In 234 flocks that were sampled, strains from 10 different IBV genotypes were detected: the 793B genotype was detected most frequently, followed by QX, Massachusetts (Mass) and the Xindadi-like strains. Strains belonging to the Q1, Ark, D274, D1466, Italy-02 and B1648 genotypes were detected as well, although less frequently. The separate sampling of tracheas and kidneys for IBV detection using reverse transcriptase PCR was very useful, as different genotypes or significant differences in sequences of the same genotype were detected between both organs. The data of this survey also provided valuable information about the replication of IBD vaccines and subsequent infectious bursal disease virus (IBDV) antibody responses under field conditions. The detection of five non-vvIBDV field strains of two different genotypes shows the presence of non-vvIBDV non-vaccine strains, which can easily be undetected in Europe due to the focus on sampling of clinically ill birds. Detection of vaccine virus in the bursa and antibody response to the IBD vaccination in flocks that had been vaccinated by the drinking water with a live attenuated vaccine compared to a vaccination in the hatchery using an immune-complex vaccine showed a delayed replication of the vaccines that had been applied by the drinking water, indicating mistakes in the timing and/or application of the vaccines.