Isolation and identification of a rabbit hemorrhagic virus type 2 strain

Abstract:

[Background] rabbit hemorrhagic disease virus 2 (RHDV2) was found in April 2020 in China, which seriously threatened the rabbit breeding industry and ecological balance. Besides, basic researches on the etiology and genetic characteristics of RHDV2 are still lacking in China. [Objective] To isolate and identify RHDV2 strain, and to conduct whole gene sequencing and genetic evolution analysis of the isolated strain. [Methods] We planned to conduct pathological dissection, RT-qPCR detection, and animal regression test to isolate and identify the RHDV2 strain in a rabbit farm suspected to have died from RHDV2 infection. [Results] Further whole gene sequencing and genetic evolution analysis were performed. The necropsies of dead rabbits showed hemorrhage and enlargement of all parenchymal organs, especially the heart, lung and liver. RHDV2 was confirmed by RT-qPCR, and there was no mixed infection with other pathogens. We found the infected rabbits could cause similar lesions. The isolates were named SCCN03, and the gene sequences is 7 464 bp in length, which was about 99.21% consistent with the reference strain (GenBank accession number: MN901451.1). By comparing the amino acid sequence of the reference strain, many missense mutations occurred in the amino acid sequence of the non-structural proteins and structural proteins in the isolated strain, among which several missense mutations of the non-structural proteins P16 and structural proteins may be related to the variation of the virus strain. The evolutionary tree showed that SCCN03 belonged to GI.2 genotype. [Conclusion] One strain of RHDV2 was isolated and identified, and its gene sequence was obtained, which enriched the whole genetic data of RHDV2 and laid a foundation for subsequent studies on virulence of RHDV and related vaccine development.

Key words:rabbit hemorrhagic disease virus 2, isolation and identification, whole gene sequencing, genetic evolution analysis