Isolation of four serotypes of epizootic hemorrhagic disease virus from Culicoides spp. and their associated infections in cattle in Yunnan, China.

Epizootic hemorrhagic disease (EHD) is a noncontagious viral infection transmitted by certain species of the genus Culicoides and has been included on the World Organization for Animal Health (OIE) list of diseases affecting domestic and wild ruminants. This study isolated four serotypes of EHDV strains (EHDV-1, -5, -6, and -7) from three Culicoides species collected in Yunnan Province, China. The phylogenetic analysis of Seg-3 revealed that EHDVs can be classified into two groups based on their geographical origins: Eastern and Western. The four isolates examined in this study belong to the Eastern group and are genetically most similar to EHDVs found in Japan and Australia. In the Seg-2 and Seg-6 phylogenetic trees, all EHDV serotypes can be classified into four clusters (Groups A-D). The four strains were categorized into Groups A, B, C, and D and belong to the EHDV-1, -5, -6, and -7 serotypes, respectively. Sero-epidemiological surveys were conducted on cattle in the border areas of China, Laos, Myanmar, and Vietnam using C-ELISA and neutralization tests. The rate of EHDV antibody positivity ranged from 29.22% to 58.86%, with an average of 43.09%. These surveys also revealed the presence of seven serotypes of EHDV circulating among cattle in these regions, resulting in diverse prevalence rates and spatial distributions. This finding indicates that EHDV circulates among natural vectors and infects local domestic cattle in these areas. The data gathered herein will help monitor the evolutionary characteristics of EHDV and its potential to cause outbreaks in China and neighboring countries.

Importance: EHDV is the causative agent of epizootic hemorrhagic disease (EHD), a viral illness with significant implications for animal welfare, society, and the economy. There are reports of EHDV-1, -6, -7, and -10 serotypes isolated from China, but no reports of EHDV-5 strains have been documented. Here, we report the isolation and identification of four serotypes of EHDV (EHDV-1, -5, -6, and -7) from three Culicoides species (C. tainanus, C. oxystoma, and C. jacobsoni) collected in Yunnan, China. Phylogenetic analysis revealed that the four strains of EHDV are most closely related to the Australian and Japanese strains. Sero-epidemiological survey results showed that in the border areas of China, Laos, Myanmar, and Vietnam, the rate of EHDV antibody positivity ranged from 29.22% to 58.86%, and seven serotypes of EHDVs circulating among cattle in these regions presented diverse prevalence rates and spatial distributions. This finding indicates that EHDV not only circulates among natural vectors but also infects local domestic cattle in these areas and that the EHDVs prevalent in the Asia-Pacific region may share a common gene pool.