Pathogenicity and transmissibility differences in goose-originated subgenotype 3 duck Tembusu virus in goose embryos and 3-day-old goslings

The Duck Tembusu virus (DTMUV) was first reported in China in 2010 and has since caused substantial economic losses in the poultry breeding industry. In the autumn of 2022, an outbreak of an infectious disease resembling DTMUV was reported in Guangdong Province, China, which caused significantly high mortality in goose embryos, and decreased egg production. This study identified one strain of the new subgenotype 3 of DTMUV, designated as DTMUV GDZQ2022, responsible for these effects. Comprehensive genomic sequencing of this strain was conducted to analyse its genetic variations. Additionally, the isolated and purified virus was inoculated into goose embryos and goslings to assess its pathogenicity. The GDZQ2022 genome displayed over 88% nucleotide homology with other DTMUV strains from China and Southeast Asia. Phylogenetic analysis of the E gene classified GDZQ2022 within the subgenotype 3 of DTMUV. Pathogenicity experiments on goose embryos and goslings showed that the GDZQ2022 strain induced typical clinical signs of DTMUV, particularly severe neurological manifestations. Although GDZQ2022 exhibited high virulence in goose embryos, its virulence in goslings was minimal, resulting in a low mortality rate. Pathological examinations detected significant histological lesions in the brains, livers, and spleens of the infected goslings. In conclusion, this study presents the first evidence of a novel DTMUV strain proliferating among young geese in China, underscoring the genetic diversity of DTMUV and contributing to our understanding of the pathogenicity of the subgenotype 3 Tembusu virus in goose embryos and goslings.