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IBV genotype QX causes suficient disease in Europe for several commercial companies to have started developing live attenuated vaccines. Here, one of those vaccines (L1148) was fully consensus sequenced alongside its progenitor ield strain (1148-A) to determine vaccines markers, thereby enabling detection on farms. Twenty eight single nucleotide substitutions were associated with the 1148-A attenuation, of which any combination can identify vaccine L1148 in the ield. Sixteen substitutions resulted in amino acid coding changes of which half were in spike. One change in the 1b gene altered the normally highly conserved inal 5 nucleotides of the transcription regulatory sequence of the S gene, common to all IBV QX genes. No mutations can currently be associated with the attenuation process. Field vaccination strategies would greatly beneit by such comparative sequence data being mandatorily submitted to regulators prior to vaccine release following a successful registration process

Since 1996 a new Infectious Bronchitis virus (IBV) genotype, referred to as Q1, circulated in China and was reported for the Þ rst time in Italy in 2011, associated with an increase of mortality, kidney lesions and proventriculitis. During a 2013 Northern Italian outbreak of respiratory disease in a chicken ß ock, an IBV strain was detected by RT-PCR and characterized as Q1-like. The virus was isolated and named CoV/ Ck/Italy/I2022/13. All coding regions of the isolate were sequenced and compared with 130 complete genome sequences of IBV and TCoV, downloaded from ViPR, and showed most identity with a Chinese strain CK/CH/LDL/97I (p-distance=0.044). To identify potential recombination events a complete genome SimPlot analysis was carried out which revealed the presence of possible multiple recombination events, but the minor parent strains remained unknown. A phylogenetic analysis of the complete S1 gene was performed using all complete S1 sequences available on ViPR and showed that the isolate clustered with an Q1-like strain isolated in Italy in 2011 (p-distance=0.004) and a group of Chinese Q1-like strains isolated from the mid 90’s (p-distance=0.001 with GenBank Accession Number CK 577410). It could be hypothesized that the isolate descended from the Italian 2011 Q1-like strain or was the result of a separate introduction from China, through commercial trade or migratory birds; but the data did not distinguish between these possibilities