Complete genome sequence and biological characteristics of a novel duck enteritis virus variant with a deletion in UL2

A virulent duck enteritis virus (DEV) isolate, designated DEV JS2024, was obtained from diseased ducks on a routinely vaccinated duck farm in Jiangsu Province. The complete genome sequence of this isolate was determined and found to be 161,600 bp in length. The UL2 of DEV JS2024 is 474 bp in length and was found to be completely identical to that of a commercially available attenuated DEV vaccine (GenBank accession number KF487736). However, it was found to have a continuous 528-bp deletion when compared with the Chinese standard virulent strain (GenBank accession number JQ673560). In addition, there were point mutations in UL32, UL20, UL14, UL7, RS1, and US5. Ducks infected with DEV JS2024 showed characteristic DEV pathology, including clinical manifestations and pathological lesions. The titer of DEV JS2024 in ducks was 10⁵ LD₅₀/mL. Our findings suggest that the 528-bp deletion in the UL2 gene is likely to have been generated through recombination between an attenuated vaccine strain and a wild-type virulent strain. This is the first report of a probable natural DEV recombination event identified in the field. .