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

Serological evidence of epizootic hemorrhagic disease and serotypes of epizootic hemorrhagic disease virus in Pakistan

This study investigated seroprevalence and serotypes of Epizootic hemorrhagic disease virus (EHDV) in ruminants in North-Western Pakistan. A total of 616 serum samples were tested for the presence of antibodies against EHDV and neutralizing antibodies against 7 EHDV serotypes (EHDV-1, 2, 4, 5, 6, 7 and 8) using competitive ELISA and VNT, respectively. The overall seroprevalence of EHDV was found to be 35.9%. Seroprevalence of EHDV in cattle, buffalo and goats was found as 66.9, 21.3 and 4.1%, respectively. In multivariate analysis, the seroprevalence of EHDV was found 12.8 (95% CI = 6.1-27) times higher in cattle than buffalo and 3.3 (95% CI = 1.4-10) times higher in buffalo than goats. The seroprevalence was found to be 6 (95% CI = 3.2-11.3) times higher in old animals than in young ones. The seroprevalence was recorded as 4.8 (95% CI = 2.3-10) and 2.1 (95% CI = 1.3-3.6) times higher in the Southern and Central zones, respectively than in the Northern zone of the study area. Neutralizing antibodies against six different serotypes of EHDV (EHDV-1, 2, 5, 6, 7 and 8) were detected. Neutralizing antibodies against EHDV-6 was found to be the most prevalent (62.1%) and those against EHDV-1 as the least prevalent (11.2%). This study shows that Epizootic hemorrhagic disease (EHD) is prevalent in Pakistan and at least six different serotypes of EHDV have circulated or are circulating in the country. Virological studies are required to investigate the currently circulating serotypes of EHDV in the country.

Searching for potential Culicoides vectors of four orbiviruses in Yunnan Province, China

BACKGROUND

Some species of Culicoides (Diptera, Ceratopogonidae) are major vectors for arboviruses, and Yunnan Province is a key area for arbovirus prevalence in China. Therefore, this study attempts to search for potential Culicoides vectors for the common orbiviruses bluetongue virus (BTV), epizootic hemorrhagic disease virus (EHDV), Palyam virus (PALV) and Tibet orbivirus (TIBOV) in Yunnan Province, China.

METHODS

Culicoides specimens were collected from 16 counties in Yunnan Province, China, using UV traps and tested for BTV, EHDV, PALV and TIBOV through one-step reverse transcription-quantitative polymerase chain reaction (RT-qPCR). A total of 543 conspecific pools of Culicoides containing 9895 specimens were tested.

RESULTS

A total of 46 species belonging to 8 subgenera and 2 groups were recognized. A total of 19 species and a Culicoides subgenus Trithecoides complex were tested using RT-qPCR. One pool of Culicoides shortti Smith & Swaminath and one pool of Culicoides orientalis Macfie tested positive for BTV, one pool of Culicoides oxystoma Kieffer tested positive for PALV, and four pools of Culicoides jacobsoni Macfie tested positive for TIBOV. All the tested samples were negative for EHDV, and all the tested C. subgenus Trithecoides midges were negative for any virus.

CONCLUSIONS

Culicoides shortti was identified as a potential BTV vector for the first time. Culicoides jacobsoni was confirmed as a potential TIBOV vector and C. orientalis as a potential BTV vector. Culicoides oxystoma was also shown to be a natural carrier of PALV using the RT-qPCR method.

Culicoides and midge-associated arboviruses on cattle farms in Yunnan Province, China

Culicoides spp. (Diptera: Ceratopogonidae) are small biting midges, some of which are the vectors of arboviruses affecting livestock, i.e., African horse sickness virus (AHSV), bluetongue virus (BTV), and epizootic hemorrhagic disease virus (EHDV). Yunnan Province, located in southwestern China, has a history of high prevalence of arboviruses. The diversity and abundance of Culicoides was observed between March 2022 and March 2023 on two cattle farms in Lufeng County of Yunnan Province, China and virus isolation and PCR detection were attempted from cattle blood and Culicoides spp. collected from the farms. Light trap collections contained 19 species of Culicoides belonging to 8 subgenera and one unplaced species group and were dominated by C. oxystoma (63.4%), C. imicola (16.2%), C. arakawae (13.4%), C. sp. near newsteadi (2.3%), and C. orientalis (1.7%). A total of 8,343 Culicoides were used for statistical analysis; from these collections 997 Culicoides specimens belonging to 10 species were screened for the presence of BTV, EHDV, Yunnan Orbivirus (YUOV), and Yongshan totivirus (YSToV) using reverse transcription quantitative PCR (RT-qPCR). One strain of YUOV was isolated from cattle blood and 7 isolates of YSToV were isolated from 5 different species of Culicoides. BTV and YSToV were detected from 2 and 3 pools of parous C. imicola specimens by RT-qPCR, respectively, which is the first report of a totivirus to be associated with Culicoides. Culicoides imicola is likely to be the major vector of Culicoides-borne arboviruses in Lufeng County, which is a relatively dry locality, and adult C. imicola may play a role of BTV overwintering.

Isolation of Epizootic Hemorrhagic Disease Virus Serotype 10 from Culicoides tainanus and Associated Infections in Livestock in Yunnan, China

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.

Complete genome sequences of epizootic hemorrhagic disease virus serotypes 5 and 6 isolated in Japan

Here, we report the complete genome sequences of epizootic hemorrhagic disease (EHD) virus serotypes 5 (EHDV-5) and 6 (EHDV-6) isolated in the Yaeyama Islands of Okinawa Prefecture, Japan. The EHDV-5 strain, ON-11/E/16, which was isolated in 2016, is, to our knowledge, the second EHDV-5 strain to be isolated after the first was isolated in Australia in 1977. In each of the genome segments, ON-11/E/16 was most closely related to EHDV strains of different serotypes isolated in Australia and Japan. Our results support the idea that various serotypes of EHDV have been circulating while causing reassortment in the Asia-Pacific region. In all genome segments, the EHDV-6 strain, ON-3/E/14, which was isolated in 2014, was highly similar to EHDV-6 strain HG-1/E/15, which was detected in affected cattle during the EHD epidemic in Hyogo prefecture in 2015. Therefore, these two EHDV-6 strains, ON-3/E/14 and HG-1/E/15, may have the same origin. However, it is unclear whether EHDV-6 was transmitted directly between the locations where those strains were isolated/detected (approx. 1,500 km apart) or whether EHDV-6 strains of the same origin entered each location at different times. In addition, we cannot rule out the possibility that EHDV-6 infection has spread unnoticed through asymptomatic cattle in other areas of Japan. Therefore, further investigation into EHDV infection in cattle is necessary for a more detailed understanding of the ecology of EHDV in Japan.

Current Knowledge on Epizootic Haemorrhagic Disease in China

Epizootic haemorrhagic disease (EHD) is an infectious, non-contagious viral disease of ruminants caused by epizootic haemorrhagic disease virus (EHDV) and is transmitted by insects of the genus Culicoides. In 2008, EHD was listed on the World Organization for Animal Health (WOAH) list of notifiable terrestrial and aquatic animal diseases. This article reviews the distribution of EHD in China and relevant studies and proposes several suggestions for the prevention and control of EHD. There have been reports of positivity for serum antibodies against EHDV-1, EHDV-2, EHDV-5, EHDV-6, EHDV-7, EHDV-8 and EHDV-10 in China. Strains of EHDV-1, -5, -6, -7, -8 and -10 have been isolated, among which the Seg-2, Seg-3 and Seg-6 sequences of serotypes -5, -6, -7 and -10 belong to the eastern topotype. The emergence of western topotype Seg-2 in EHDV-1 strains indicates that EHDV-1 strains in China are reassortant strains of the western and eastern topotypes. A novel serotype strain of EHDV named YNDH/V079/2018 was isolated in 2018. Chinese scholars have successfully expressed the EHDV VP7 protein and developed a variety of ELISA detection methods, including antigen capture ELISA and competitive ELISA. A variety of EHDV nucleic acid detection methods, including RT-PCR and qRT-PCR, have also been developed. LAMP and the liquid chip detection technique are also available. To prevent and control EHD, several suggestions for controlling EHD transmission have been proposed based on the actual situation in China, including controlling the number of Culicoides, reducing contact between Culicoides and hosts, continued monitoring of EHDV and Culicoides in different areas of China and further development and application of basic and pioneering research related to EHD prevention and control.

Seroprevalence of Epizootic Hemorrhagic Disease Virus in Guangdong Cattle Farms during 2013-2017, China

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.

Circulation of Bluetongue Virus Serotypes 1, 4, 8, 10 and 16 and Epizootic Hemorrhagic Disease Virus in the Sultanate of Oman in 2020-2021

The circulation of Bluetongue (BT) and Epizootic Hemorrhagic Disease (EHD) in the Middle East has already been reported following serological analyses carried out since the 1980s, mostly on wild ruminants. Thus, an EHD virus (EHDV) strain was isolated in Bahrain in 1983 (serotype 6), and more recently, BT virus (BTV) serotypes 1, 4, 8 and 16 have been isolated in Oman. To our knowledge, no genomic sequence of these different BTV strains have been published. These same BTV or EHDV serotypes have circulated and, for some of them, are still circulating in the Mediterranean basin and/or in Europe. In this study, we used samples from domestic ruminant herds collected in Oman in 2020 and 2021 for suspected foot-and-mouth disease (FMD) to investigate the presence of BTV and EHDV in these herds. Sera and whole blood from goats, sheep and cattle were tested for the presence of viral genomes (by PCR) and antibodies (by ELISA). We were able to confirm the presence of 5 BTV serotypes (1, 4, 8, 10 and 16) and the circulation of EHDV in this territory in 2020 and 2021. The isolation of a BTV-8 strain allowed us to sequence its entire genome and to compare it with another BTV-8 strain isolated in Mayotte and with homologous BTV sequences available on GenBank.

Epizootic Hemorrhagic Disease Virus: Current Knowledge and Emerging Perspectives

Epizootic Hemorrhagic Disease (EHD) of ruminants is a viral pathology that has significant welfare, social, and economic implications. The causative agent, epizootic hemorrhagic disease virus (EHDV), belongs to the Orbivirus genus and leads to significant regional disease outbreaks among livestock and wildlife in North America, Asia, Africa, and Oceania, causing significant morbidity and mortality. During the past decade, this viral disease has become a real threat for countries of the Mediterranean basin, with the recent occurrence of several important outbreaks in livestock. Moreover, the European Union registered the first cases of EHDV ever detected within its territory. Competent vectors involved in viral transmission, Culicoides midges, are expanding its distribution, conceivably due to global climate change. Therefore, livestock and wild ruminants around the globe are at risk for this serious disease. This review provides an overview of current knowledge about EHDV, including changes of distribution and virulence, an examination of different animal models of disease, and a discussion about potential treatments to control the disease.