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

Abstract

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.

Attenuated live infectious bronchitis virus QX vaccine disseminates slowly to target organs distant from the site of inoculation

“…These viruses are associated with respiratory problems, renal failure, drops in egg production and 'false layers' syndrome [5][6][7][8][9]. In Europe, it is the second most prevalent IBV genotype [10].…”

Three Amino Acid Changes in Avian Coronavirus Spike Protein Allow Binding to Kidney Tissue

“…affected depend primarily on the IBV strain (2). Phylogenetic classification of IBV strains results in 32 phylogenetic lineages (GI-1 to GI-27 and GII to GVI) (3), of which GI-1 includes historically the first IBV genotype identified, Massachusetts (IBV-Mass).…”

“…Phylogenetic classification of IBV strains results in 32 phylogenetic lineages (GI-1 to GI-27 and GII to GVI) (3), of which GI-1 includes historically the first IBV genotype identified, Massachusetts (IBV-Mass). IBV-Mass infections are reported worldwide, and in Europe, GI-1 is currently the 3rd most prevalent genotype (2). The more prevalent IBV genotype circulating in Europe is IBV-QX (GI-19) (2,3), which has been reported to cause kidney disease in contrast to IBV-Mass (2).…”

Infectious bronchitis virus Mass-type (GI-1) and QX-like (GI-19) genotyping and vaccine differentiation using SYBR green RT-qPCR paired with melting curve analysis

“…To this purpose we first developed and validated a protocol to differentiate vaccine Poulvac IB QX from QX-like field strains using three distinct vaccine makers arose during the attenuation process (Listorti et al, 2017). Then we developed a multiplex protocol for IBV genotyping, focusing on QX-like (GI-19) and Mass-type (GI-1) strains, being two of the most widespread IBV genotypes (Cook et al, 2012;de Wit et al, 2018;Jackwood et al, 2012).…”

“…Those unique vaccine markers affecting the GC content of the target region were targeted to develop a SYBRgreen RT-qPCR assay enabling the differentiation of vaccine Poulvac IB QX from QX-like field strains via melting curve analysis. Next we developed a multiplex assay for the simultaneous genotyping of IBV Mass-type (lineage GI-1) and IBV QXlike (lineage GI-19) strains, as those two genotypes represent a major threat for the poultry industry worldwide (Cook et al, 2012;de Wit et al, 2018;Jackwood et al, 2012). To achieve this, specific primer sets were designed and RT-qPCR and SYBRgreen analysis settings were optimized in order to detect and differentiate the sequence variants of interest.…”