Two strains of viruses, JC13C644 and JC13C673, were isolated from Culicoides tainanus collected in Jiangcheng County, Yunnan Province, situated along the border area shared by China, Laos, and Vietnam. JC13C644 and JC13C673 viruses can cause cytopathic effect (CPE) in mammalian cells BHK21 and Vero cells, and cause morbidity and mortality in suckling mice 48 h after intracerebral inoculation. Whole-genome sequencing was performed, yielding complete sequences for all 10 segments from Seg-1 (3942nt) to Seg-10 (810nt). Phylogenetic analysis of the sub-core-shell (T2) showed that the JC13C644 and JC13C673 viruses clustered with the Epizootic Hemorrhagic Disease Virus (EHDV) isolated from Japan and Australia, with nucleotide and amino acid homology of 93.1% to 98.3% and 99.2% to 99.6%, respectively, suggesting that they were Eastern group EHDV. The phylogenetic analysis of outer capsid protein (OC1) and outer capsid protein (OC2) showed that the JC13C644 and JC13C673 viruses were clustered with the EHDV-10 isolated from Japan in 1998, with the nucleotide homology of 98.3% and 98.5%, and the amino acid homology of 99.6% and 99.6–99.8%, respectively, indicating that they belong to the EHDV-10. Seroepidemiological survey results demonstrated that JC13C644 virus-neutralizing antibodies were present in 29.02% (177/610) of locally collected cattle serum and 11.32% (89/786) of goat serum, implying the virus’s presence in Jiangcheng, Yunnan Province. This finding suggests that EHDV-10 circulates not only among blood-sucking insects in nature but also infects local domestic animals in China. Notably, this marks the first-ever isolation of the virus in China and its discovery outside of Japan since its initial isolation from Japanese cattle. In light of these results, it is evident that EHDV Serotype 10 exists beyond Japan, notably in the natural vectors of southern Eurasia, with the capacity to infect local cattle and goats. Therefore, it is imperative to intensify the surveillance of EHDV infection in domestic animals, particularly focusing on the detection and monitoring of new virus serotypes that may emerge in the region and pose risks to animal health.

Background: Tibet Orbivirus (TIBOV) is a recently discovered Orbivirus known to infect cattle, Asian buffalo and goats in south-western China. It was first isolated from mosquitoes and subsequently from biting midges (Culicoides spp.) in Yunnan, China, indicating that it is an arbovirus. Little is known of its potential to cause disease, but the economic importance of related viruses promoted an investigation of potential Culicoides spp. vectors of TIBOV. Methods: Biting midges were collected approximately once per week between May and December 2020, at a cattle farm in Wulong village, Shizong County, Yunnan Province, China. Approximately 3000 specimens of nine species were subsequently used in attempts to isolate virus, and a further 2000 specimens of six species were tested for the presence of bluetongue virus (BTV) and TIBOV using a RT-qPCR test. Results: Virus isolation attempts resulted in the isolation of three viruses. One isolate from a pool of Culicoidesjacobsoni was identified as TIBOV, while the other two viruses from C.orientalis and C.tainanus remain unidentified but are not BTV or TIBOV. RT-qPCR analysis did not detect BTV in any specimens, but a single pool containing five specimens of C. jacobsoni and another containing five specimens of C. tainanus produced PCR quantification cycle (Cq) values of around 28 that may indicate infection with TIBOV. Conclusions: The isolation of TIBOV from C. jacobsoni satisfies one criterion required to prove its status as a vector of this virus. This isolation is supported by a low Cq value produced from a different pool of this species in the RT-qPCR test. The low Cq value obtained from a pool of C. tainanus suggests that this species may also be able to satisfy this criterion. Both of these species are widespread throughout Asia, with C. jacobsoni extending into the Pacific region, which raises the possibility that TIBOV may be more widespread than is currently known. Graphical

Epizootic hemorrhagic disease (EHD) is an infectious viral disease caused by epizootic hemorrhagic disease virus (EHDV) and EHDV frequently circulates in wild and domestic ruminants. Sporadic outbreaks of EHD have caused thousands of deaths and stillbirths on cattle farms. However, not much is known about the circulating status of EHDV in Guangdong, southern China. To estimate the seroprevalence of EHDV in Guangdong province, 2886 cattle serum samples were collected from 2013 to 2017 and tested for antibodies against EHDV using a competitive ELISA. The overall seroprevalence of EHDV reached 57.87% and was highest in autumn (75.34%). A subset of positive samples were serotyped by a serum neutralization test, showing that EHDV serotypes 1 and 5–8 were circulating in Guangdong. In addition, EHDV prevalence always peaked in autumn, while eastern Guangdong had the highest EHDV seropositivity over the five-year period, displaying apparent temporal–spatial distribution of EHDV prevalence. A binary logistic model analysis indicated a significant association between cattle with BTV infections and seroprevalence of EHDV (OR = 1.70, p < 0.001). The co-infection of different serotypes of EHDV and BTV raises a high risk of potential genomic reassortment and is likely to pose a significant threat to cattle, thus urging more surveillance to monitor their circulating dynamics in China.

Sedoreoviridae is a family of viruses belonging to the order Reovirales and comprises six genera, two of which, Orbivirus and Seadornavirus, contain arboviruses that cause disease in humans and livestock. Areas such as Yunnan Province in southwestern China, have high arboviral activity due in part to warm and wet summers, which support high populations of biting flies such as mosquitoes and Culicoides. Three viral isolates previously obtained from Culicoides collected at cattle farms in Shizong County of Yunnan Province, China, between 2019 and 2020 were completely sequenced and identified as Banna virus (BAV) genotype A of Seadornavirus and serotypes 1 and 7 of epizootic hemorrhagic disease virus (EHDV) of Orbivirus. These results suggest that Culicoidestainanus and C. orientalis are potential vectors of BAV and EHDV, respectively, and represent the first association of a BAV with C. tainanus and of an arbovirus with C. orientalis. Analysis using VP9 generally agreed with the current groupings within this genus based on VP12, although the classification for some strains should be corrected. Furthermore, the placement of Kadipiro virus (KDV) and Liao ning virus (LNV) in Seadornavirus may need confirmation as phylogenetic analysis placed these viruses as sister to other species in the genus.

Duan YL, et al. J Vet Sci. 2023 Jan;24:e18. https://doi.org/10.4142/jvs.22194

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.