A serologic investigation of epizootic hemorrhagic disease virus in China between 2014 and 2019

Epizootic hemorrhagic disease virus (EHDV) is a member of the genus Orbivirus, family Sedoreoviridae. It was firstly recognized in 1955 to cause a highly fatal disease of wild white-tailed deer in America. So far, EHDV was detected and isolated in many wild or domestic ruminants, and widely distributed all over the world. Although the domestic cattle and sheep infected by EHDV were usually asymptomatic or subclinical, several outbreaks of epizootic hemorrhagic disease (EHD) in deer and cattle had been reported. Many EHDV strains were isolated and sequenced in last two decades in China, which promoted a general serologic investigation of EHDV in China. In this study, 18,122 sera were collected from asymptomatic or subclinical domestic ruminants (cattle, cow, yaks, sheep, goats, and deer) in 116 regions belonging to 15 provinces in China. All the sera were tested by EHDV C-ELISA, and the results were obtained by big data analysis. EHDV infections were detected in the 14 of 15 provinces, and only Tibet (average altitude ≥ 4000 m) which was the highest province in China was free of EHDV. The numbers of seropositive collections in both bovine and goat/sheep were in an inverse proportion to the latitude. However, the seropositive rates in bovine were ranged from 0% to 100%, while the seropositive rates in goat/sheep were no more than 50%. The results suggested that bovine was obviously more susceptive for EHDV infection than goat and sheep, therefore might be a major reservoir of EHDV in China. The prevalence of EHDV was consistent with the distribution of Culicoides which were known as the sole insect vectors of EHDV. In particular, the seropositive rates of EHDV were very high in the southern provinces, which required the enhanced surveillance in the future.