Discovery and whole-genome analysis of a novel highly pathogenic duck plague virus with a frameshift mutation in LORF2, China

Duck plaguevirus (DPV), an alpha herpesvirus, causes major economic losses in global aquaculture and livestock sectors and is a primary cause of recurrent disease outbreaks in Chinese waterfowl industry. In this study, a strain named GXGG240520 was isolated in Guangxi region. The UL2 gene sequencing analysis revealed that this strain belonged to a highly virulent DPV strain with high homology to the Asian CHv strain. Subsequently, the pathogenicity assessment indicated that single infection with the Guangxi isolate could cause severe tissue hemorrhage and immune organ atrophy in ducks, with a mortality rate of up to 90%.To systematically investigate the specificity of DPV in Guangxi region, we conducted animal protection trials and whole-genome sequencing on the isolated strain. Upon challenging ducks that had attained antibody protection levels, a 60% mortality rate was observed, in stark contrast to the 100% mortality rate in non-immunized ducks. Whole-genome sequencing revealed a 162,188 bp genome, and subsequent analysis of homology and amino acid sequences across 78 open reading frames (ORFs) identified 41 amino acid site mutations in 27 ORFs. Homologous recombination analysis confirmed that the isolated strain was a recombinant product derived from CHv and YLDRBP11 strains. Notably, compared with the currently referenced LORF2 gene of DPV, the LORF2 gene unique to avian herpesviruses in this isolated strain had premature termination codons.Overall, this study provides critical insights into the genetic evolution, pathogenicity, and prevention of DPV in Guangxi, offering valuable references for regional disease control strategies.