Abstract:

This study was designed to understand the prevalence and genetic evolution of field strains of lumpy skin disease (LSD) in cattle in our country, and determine the biological characteristics of lumpy skin disease virus (LSDV). This study conducted PCR testing, virus isolation, immunofluorescence identification, electron microscopy observation, GPCR gene sequencing, and genetic evolution analysis on skin nodule samples from cattle suspected of having lumpy skin disease. The results indicate that the disease affecting cattle in three provinces in our country is Lumpy Skin Disease. Three LSDV strains were isolated using primary lamb testicular cells (PLT) and named LSDV/Heilongjiang/2022, LSDV/Jiling/2022, and LSDV/Jiangxi/2022. The growth curve of the three viruses showed the fastest growth rate in the first 96 hours, with the highest titer at 96 to 120 hours. Afterward, the virus growth rate started to slow down, and the highest titer was reached 96 hours after inoculation, the titers for the three strains were 10^6.0 TCID₅₀·mL^-1, 10^5.3 TCID₅₀·mL^-1, and 10^5.1 TCID₅₀·mL^-1, respectively. Under transmission electron microscopy, virus particles appeared elliptical, with a diameter between 200 and 300 nm. Genetic evolution analysis of the GPCR gene sequences of the three strains, along with prevalent strains in various regions of China and other countries in recent years, showed that the three isolated strains and the prevalent strains in various regions of China are on the same branch. This indicates a strong correlation in the prevalence of Lumpy Skin Disease in various regions of China. This study successfully isolated three strains of LSDV from skin nodules of cattle in Heilongjiang, Jilin, and Jiangxi provinces, enriching the epidemiological and pathogenic data of LSDV in China. It holds significant importance for the continuous monitoring of LSDV and the development of new vaccines.

Key words: lumpy skin disease virus, isolation and identification, biological characteristics, phylogenetic analysis