Identification and PCR-restriction fragment length polymorphism analysis of a variant of the Ibaraki virus from naturally infected cattle and aborted fetuses in Japan

The Molecular Epidemiology of Epizootic Hemorrhagic Disease Viruses Identified in Israel between 2015 and 2023

Epizootic hemorrhagic disease (EHD) is an infectious, non-contagious viral disease seriously affecting cattle and some wild ruminants and has a worldwide distribution. All viruses can be subdivided into "Eastern" and "Western" topotypes according to geographic distribution via the phylogenetic analysis of internal genes. In Israel, during the last decade, three outbreaks were registered: caused by EHDV-6 in 2015, by EHDV-1 in 2016, and by EHDV-7 in 2020. Additionally, RNA of EHDV-8 was found in imported calves from Portugal in 2023. During the same period in other countries of the region, non-Israeli-like EHDV-6 and EHDV-8 were identified. Full genome sequencing, BLAST, and phylogenetic analyses of the locally and globally known EHDV genomes allowed us to presume the probable route and origin of these viruses detected in Israel. Thus, EHDV-6 has probably been circulating in the region for a long period when EHDV-1 and -8 appeared here for the last years, while their route of introduction into the new areas was probably natural; all of them belonged to the "Western" topotype. In contrast, EHDV-7 probably had the "Eastern", anthropogenic origin. Data from the study can facilitate the evaluation of the appearance or reappearance of EHDVs in the Mediterranean area and enhance the planning of prevention measures.

Biting Midges (Diptera: Ceratopogonidae) as Vectors of Viruses

Biting midges of the genus Culicoides occur almost globally and can regionally and seasonally reach high abundances. Most species are hematophagous, feeding on all groups of vertebrates, including humans. In addition to being nuisance pests, they are able to transmit disease agents, with some viruses causing high morbidity and/or mortality in ruminants, horses and humans. Despite their impact on animal husbandry, public health and tourism, knowledge on the biology and ecology of culicoid biting midges and their interactions with ingested pathogens or symbiotic microorganisms is limited. Research is challenging due to unknown larval habitats, the insects' tiny size, the inability to establish and breed most species in the laboratory and the laborious maintenance of colonies of the few species that can be reared in the laboratory. Consequently, the natural transmission of pathogens has experimentally been demonstrated for few species while, for others, only indirect evidence of vector potential exists. Most experimental data are available for Culicoides sonorensis and C. nubeculosus, the only species kept in western-world insectaries. This contribution gives an overview on important biting midge vectors, transmitted viruses, culicoid-borne viral diseases and their epidemiologies and summarizes the little knowledge on interactions between biting midges, their microflora and culicoid-borne arboviruses.

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.

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.

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This is a big data analysis.

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This is the first English report for EHDV prevalence in multiple provinces in China.

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The samples included in this study cover 15 provinces and 6 years.

Isolation of Culicoides- and Mosquito-Borne Orbiviruses in the Southwestern Islands of Japan Between 2014 and 2019

The circulation of arboviruses in livestock ruminants has often gone unrecognized owing to the fact that a significant percentage of arboviruses probably induce subclinical infections and/or negligible symptoms in infected animals. To determine the current situation of arbovirus circulation in the Yaeyama Islands, attempts to isolate viruses from bovine blood samples collected between 2014 and 2019 have been made. In total, 308 blood samples were collected during the study period, and 43 of them induced cytopathic effects (CPEs) in cell cultures. The identification of the CPE agents was performed by reported RT-PCR assays and a high-throughput analysis with a next-generation sequencing platform. The obtained viruses consisted of an orthobunyavirus (Peaton virus), Culicoides-borne orbiviruses (bluetongue virus serotypes 12 and 16, epizootic hemorrhagic disease virus [EHDV] serotypes 5, 6, and 7, D'Aguilar virus, and Bunyip Creek virus), and potential mosquito-borne orbiviruses (Yunnan orbivirus, Guangxi orbivirus, and Yonaguni orbivirus). Most of the orbiviruses were recovered from washed blood cells with mosquito cell cultures, suggesting that this combination was more efficient than other combinations such as plasma/blood cells and hamster cell lines. This marked the first time that the isolation of EHDV serotypes 5 and 6 and three potential mosquito-borne orbiviruses was recorded in Japan, showing a greater variety of orbiviruses on the islands than previously known. Genetic analysis of the isolated orbiviruses suggested that the Yaeyama Islands and its neighboring regions were epidemiologically related. Some of the viruses, especially the potential mosquito-borne orbiviruses, were isolated during several consecutive years, indicating their establishment on the islands.

Endemic and Emerging Arboviruses in Domestic Ruminants in East Asia

Epizootic congenital abnormalities caused by Akabane, Aino, and Chuzan viruses have damaged the reproduction of domestic ruminants in East Asia for many years. In the past, large outbreaks of febrile illness related to bovine ephemeral fever and Ibaraki viruses severely affected the cattle industry in that region. In recent years, vaccines against these viruses have reduced the occurrence of diseases, although the viruses are still circulating and have occasionally caused sporadic and small-scaled epidemics. Over a long-term monitoring period, many arboviruses other than the above-mentioned viruses have been isolated from cattle and Culicoides biting midges in Japan. Several novel arboviruses that may infect ruminants (e.g., mosquito- and tick-borne arboviruses) were recently reported in mainland China based on extensive surveillance. It is noteworthy that some are suspected of being associated with cattle diseases. Malformed calves exposed to an intrauterine infection with orthobunyaviruses (e.g., Peaton and Shamonda viruses) have been observed. Epizootic hemorrhagic disease virus serotype 6 caused a sudden outbreak of hemorrhagic disease in cattle in Japan. Unfortunately, the pathogenicity of many other viruses in ruminants has been uncertain, although these viruses potentially affect livestock production. As global transportation grows, the risk of an accidental incursion of arboviruses is likely to increase in previously non-endemic areas. Global warming will also certainly affect the distribution and active period of vectors, and thus the range of virus spreads will expand to higher-latitude regions. To prevent anticipated damages to the livestock industry, the monitoring system for arboviral circulation and incursion should be strengthened; moreover, the sharing of information and preventive strategies will be essential in East Asia.

Development and optimization of a DNA-based reverse genetics systems for epizootic hemorrhagic disease virus

Epizootic hemorrhagic disease virus (EHDV) is a member of the genus Orbivirus, family Reoviridae, and has a genome consisting of 10 linear double-stranded (ds) RNA segments. The current reverse genetics system (RGS) for engineering the EHDV genome relies on the use of in vitro-synthesized capped viral RNA transcripts. To obtain more-efficient and simpler RGSs for EHDV, we developed an entirely DNA (plasmid or PCR amplicon)-based RGS for viral rescue. This RGS enabled the rescue of infectious EHDV from BSR-T7 cells following co-transfection with seven helper viral protein expression plasmids and 10 cDNA rescue plasmids or PCR amplicons representing the EHDV genome. Furthermore, we optimized the DNA-based systems and confirmed that some of the helper expression plasmids were not essential for the recovery of infectious EHDV. Thus, DNA-based RGSs may offer a more efficient method of recombinant virus recovery and accelerate the study of the biological characteristics of EHDV and the development of novel vaccines.

Identification and complete-genome phylogenetic analysis of an epizootic hemorrhagic disease virus serotype 7 strain isolated in China

An epizootic hemorrhagic disease virus (EHDV) strain designated YN09-04 was isolated from sentinel cattle in China. The length of its complete genome was 19,344 bp in total, consisting of 10 segments ranging in size from 810 bp (S10) to 3942 bp (S1). Based on phylogenetic analysis of the S2 sequence, YN09-04 clusters with EHDV serotype 7 (EHDV-7) strains form a distinct, well-supported subgroup, indicating that YN09-04 belongs to EHDV-7. However, the origin of the YN09-04 genome is very complex. The S2 and S6 of YN09-04 cluster with those of Japanese EHDV-7 strains, whereas the S1, S3, S4, S5 and S7 of YN09-04 share high nucleotide sequence identity and a close relationship with those of Japanese Ibaraki viruses, and the S8, S9 and S10 nucleotide sequences of YN09-04 are more similar to those of some Australian EHDV strains than to those of other isolates. These results suggest that the genome of YN09-04 likely originated from a reassortment event between EHDV strains that were similar to the current Japanese and Australian strains and that YN09-04 and some EHDVs from Japan and Australia share the same ancestors. This is the first report of the isolation, identification and complete-genome phylogenetic analysis of an EHDV-7 strain from China.

Vector Competence of Culicoides sonorensis (Diptera: Ceratopogonidae) for Epizootic Hemorrhagic Disease Virus Serotype 2 Strains from Canada and Florida

Epizootic hemorrhagic disease virus (EHDV), an Orbivirus transmitted by Culicoides spp. vectors, is represented by seven serotypes and numerous strains worldwide. While studies comparing vector competence between serotypes exist, studies between viral strains are lacking. In this study, we examined the rates of infection, dissemination, and transmission of two strains of EHDV-2 orally fed to the known vector, Culicoides sonorensis Wirth & Jones. Culicoides sonorensis cohorts were fed an infectious blood meal containing EHDV-2 strains from either Alberta, Canada (Can-Alberta) or Florida (5.5 log₁₀ PFUe/mL) and tested for the vector’s susceptibility to infection and dissemination. In addition, transmission rates of the virus were assessed and compared using capillary tube and honey card methods. Our results show that the Florida strain had higher infection and dissemination rates than the Can-Alberta strain in spite of the Florida strain having significantly lower viral titers in C. sonorensis bodies, legs, and saliva than the Can-Alberta strain. Overall transmission rates were not significantly different between the two strains but varied significantly between the methods used. These findings suggest that the consequences of EHDV infection in C. sonorensis vary between virus strains and have huge implications in future vector competence studies involving Culicoides species and Orbiviruses.

Epizootic Hemorrhagic Disease Virus Serotype 6 Infection in Cattle, Japan, 2015

During October–December 2015, an epizootic hemorrhagic disease outbreak occurred in cattle in Japan. Forty-six animals displayed fever, anorexia, cessation of rumination, salivation, and dysphagia. Virologic, serologic, and pathologic investigations revealed the causative agent was epizootic hemorrhagic disease virus serotype 6. Further virus characterization is needed to determine virus pathogenicity.

Competitive enzyme-linked immunosorbent assay using baculovirus-expressed VP7 for detection of epizootic haemorrhagic disease virus (EHDV) antibodies

Epizootic haemorrhagic disease (EHD) is a vector-borne infectious viral disease of domestic and wild ruminants. EHD could spread from infected northern African countries in free territories like the EU; therefore, the availability of diagnostic assays would represent key components for adequate surveillance and control programs. In this study, the gene encoding the VP7 protein of EHD virus (EHDV) was expressed into a baculovirus-infected insect cell system. With this unpurified protein we developed a home-made competitive ELISA (cELISA) and a total number of 275 serum samples, originating from domestic and wild ruminants, were tested. 74/275 were previously shown to be positive for EHDV antibodies by a commercially available ELISA kit. A "very good" agreement was demonstrated when compared to a commercial ELISA kit (Cohen's kappa value=0.832). Samples which caused disagreement between the two assays originated from wildlife which highlights the need for further validation by using serum samples from wild animals.

Monitoring for bovine arboviruses in the most southwestern islands in Japan between 1994 and 2014

Background

In Japan, epizootic arboviral infections have severely impacted the livestock industry for a long period. Akabane, Aino, Chuzan, bovine ephemeral fever and Ibaraki viruses have repeatedly caused epizootic abnormal births and febrile illness in the cattle population. In addition, Peaton, Sathuperi, Shamonda and D’Aguilar viruses and epizootic hemorrhagic virus serotype 7 have recently emerged in Japan and are also considered to be involved in abnormal births in cattle. The above-mentioned viruses are hypothesized to circulate in tropical and subtropical Asia year round and to be introduced to temperate East Asia by long-distance aerial dispersal of infected vectors. To watch for arbovirus incursion and assess the possibility of its early warning, monitoring for arboviruses was conducted in the Yaeyama Islands, located at the most southwestern area of Japan, between 1994 and 2014.

Results

Blood sampling was conducted once a year, in the autumn, in 40 to 60 healthy cattle from the Yaeyama Islands. Blood samples were tested for arboviruses. A total of 33 arboviruses including Akabane, Peaton, Chuzan, D’ Aguilar, Bunyip Creek, Batai and epizootic hemorrhagic viruses were isolated from bovine blood samples. Serological surveillance for the bovine arboviruses associated with cattle diseases in young cattle (ages 6–12 months: had only been alive for one summer) clearly showed their frequent incursion into the Yaeyama Islands. In some cases, the arbovirus incursions could be detected in the Yaeyama Islands prior to their spread to mainland Japan.

Conclusions

We showed that long-term surveillance in the Yaeyama Islands could estimate the activity of bovine arboviruses in neighboring regions and may provide a useful early warning for likely arbovirus infections in Japan. The findings in this study could contribute to the planning of prevention and control for bovine arbovirus infections in Japan and cooperative efforts among neighboring countries in East Asia.

Electronic supplementary material

The online version of this article (doi:10.1186/s12917-016-0747-z) contains supplementary material, which is available to authorized users.

Generation of virus like particles for epizootic hemorrhagic disease virus

Epizootic hemorrhagic disease virus (EHDV) is a distinct species within the genus Orbivirus, within the family Reoviridae. The epizootic hemorrhagic disease virus genome comprises ten segments of linear, double stranded (ds) RNA, which are packaged within each virus particle. The EHDV virion has a three layered capsid-structure, generated by four major viral proteins: VP2 and VP5 (outer capsid layer); VP7 (intermediate, core-surface layer) and VP3 (innermost, sub-core layer). Although EHDV infects cattle sporadically, several outbreaks have recently occurred in this species in five Mediterranean countries, indicating a potential threat to the European cattle industry. EHDV is transmitted by biting midges of the genus Culicoides, which can travel long distances through wind-born movements (particularly over water), increasing the potential for viral spread in new areas/countries. Expression systems to generate self-assembled virus like particles (VLPs) by simultaneous expression of the major capsid-proteins, have been established for several viruses (including bluetongue virus). This study has developed expression systems for production of EHDV VLPs, for use as non-infectious antigens in both vaccinology and serology studies, avoiding the risk of genetic reassortment between vaccine and field strains and facilitating large scale antigen production. Genes encoding the four major-capsid proteins of a field strain of EHDV-6, were isolated and cloned into transfer vectors, to generate two recombinant baculoviruses. The expression of these viral genes was assessed in insect cells by monitoring the presence of specific viral mRNAs and by western blotting. Electron microscopy studies confirmed the formation and purification of assembled VLPs.

Development of Real-Time RT-PCR Assays for Detection and Typing of Epizootic Haemorrhagic Disease Virus

Epizootic haemorrhagic disease virus (EHDV) is an emerging arboviral pathogen of wild and domestic ruminants worldwide. It is closely related to bluetongue virus (BTV) and is transmitted by adult females of competent Culicoides vector species. The EHDV genome consists of ten linear double‐stranded (ds)RNA segments, encoding five non‐structural and seven structural proteins. Genome‐segment reassortment contributes to a high level of genetic variation in individual virus strains, particularly in the areas where multiple and distinct virus lineages co‐circulate. In spite of the relatively close relationship between BTV and EHDV herd‐immunity to BTV does not appear to protect against the introduction and infection of animals by EHDV. Although EHDV can cause up to 80% morbidity in affected animals, vaccination with the homologous EHDV serotype is protective. Outer‐capsid protein VP2, encoded by Seg‐2, is the most variable of the EHDV proteins and determines both the specificity of reactions with neutralizing antibodies and consequently the identity of the eight EHDV serotypes. In contrast, VP6 (the viral helicase), encoded by Seg‐9, is highly conserved, representing a virus species/serogroup‐specific antigen. We report the development and evaluation of quantitative (q)RT‐PCR assays targeting EHDV Seg‐9 that can detect all EHDV strains (regardless of geographic origin/topotype/serotype), as well as type‐specific assays targeting Seg‐2 of the eight EHDV serotypes. The assays were evaluated using orbivirus isolates from the ‘Orbivirus reference collection’ (ORC) at The Pirbright Institute and were shown to be EHDV pan‐reactive or type‐specific. They can be used for rapid, sensitive and reliable detection and identification (typing) of EHDV RNA from infected blood, tissue samples, homogenized Culicoides, or tissue culture supernatant. None of the assays detected RNA from closely related but heterologous orbiviruses, or from uninfected host animals or cell cultures. The techniques presented could be used for both surveillance and vaccine matching (serotype identification) as part of control strategies for incursions in wild and domestic animal species.

Innocuity of a commercial live attenuated vaccine for epizootic hemorrhagic disease virus serotype 2 in late-term pregnant cows

Epizootic hemorrhagic disease (EHD) is an arthropod-borne infectious viral disease sustained by the epizootic hemorrhagic disease virus (EHDV). The only commercially available and currently used vaccines are manufactured for EHDV-2 in Japan, either live or inactivated vaccines. In this study we tested the innocuity for fetuses of the live attenuated EHDV-2 vaccine in five late-term pregnant cows. Whole blood and serum samples were collected from dams and screened for the presence of EHDV-2 RNA, infectious virus and antibodies. After calving, whole blood and serum samples collected from calves, before and after colostrum intake, were also tested for antibodies and for virus detection. In dams, neither fever nor clinical signs were observed. All of them seroconverted and a strong humoral response was detected throughout the sampling period. All blood samples tested negative for EHDV-2 except for one sample collected from a dam 11 days post-vaccination which tested positive at virus isolation at the third cell passage following two rounds of blind passages. Although they had free access to colostrum, calves tested serologically negative for EHDV-2 during the entire course of the experiment. Overall, the tested live attenuated vaccine can be safely administered to late-term pregnant cows as it was not demonstrated to cross the placental barrier. The safety of the live-attenuated vaccine is further confirmed by the emergence of Ibaraki virus in 2013 in Japan which is apparently not related to the spread of the vaccine strain currently used in Japan.

Generation of virus-like particles for emerging epizootic haemorrhagic disease virus: Towards the development of safe vaccine candidates

Epizootic haemorrhagic disease virus (EHDV) is an insect-transmitted pathogen which causes high mortality in deer populations and may also cause high morbidity in cattle. EHDV belongs to the Orbivirus genus and is closely related to the prototype Bluetongue virus (BTV). To date seven distinct serotypes have been recognized. However, a live-attenuated vaccine is commercially available against only one serotype namely EHDV-2, which has been responsible for multiple outbreaks in North America, Canada, Asia and Australia. Here we expressed four major capsid proteins (VP2, VP3, VP5 and VP7) of EHDV-1 using baculovirus multiple gene expression systems and demonstrated that three-layered VLPs were assembled mimicking the authentic EHDV particles but lacking the viral genomic RNA segments and the transcriptase complex (TC). Antibodies generated with VLPs not only neutralized EHDV-1 infection in cell culture but also showed cross neutralizing reactivity against two other serotypes, EHDV-2 and EHDV-6. For proof of concept, we demonstrated that EHDV-2 VLPs could be generated rapidly by expressing the EHDV-2 variable outer capsid proteins (VP2, VP5) together with EHDV-1 VP3 and VP7, the two inner capsid proteins, which are highly conserved among the 7 serotypes. Data presented in this study validate the VLPs as a potential vaccine and demonstrate that a vaccine could be developed rapidly in the event of an outbreak of a new serotype.

Reemergence of Ibaraki disease in southern Japan in 2013

In Japan in 2013, two cattle in the northwestern part of Kagoshima Prefecture developed fever and swallowing difficulty and were suspected of having Ibaraki disease. The epizootic hemorrhagic virus (EHDV) genome was detected from diseased and asymptomatic cattle by reverse transcription-polymerase chain reaction (RT-PCR). High neutralization antibody titers to Ibaraki virus (IBAV) ranging from 1:128 to 1:1,024 were observed in the RT-PCR-positive cattle, and the virus was isolated in one of the IBAV-positive farms. A pairwise alignment and phylogenetic analysis based on the major outer coat protein VP2 encoded in segment 2 revealed a close relationship between the isolated viruses and previous IBAV isolates. The phylogeny of VP2 also suggested that an IBAV variant isolated in 1997 was distinct from IBAV and sorted into a heterogeneous serotype, EHDV serotype 7. The findings revealed the reemergence of Ibaraki disease in Japan after a 26-year absence. Interestingly, the co-circulation of EHDV serotype 1 with IBAV was observed in the affected region, suggesting the potential reassortment between two heterogeneous serotypes in the field. Sentinel surveillance in Kagoshima Prefecture indicated that the incursion of IBAV occurred in October 2013 and that its spread was limited within the small area. Inadequate environmental temperatures for vector transmission in late autumn might have limited the virus spread to a wider region. The reemergence of Ibaraki disease showed us the importance of continuous vaccination to prevent economic losses.

Development of reverse genetics for Ibaraki virus to produce viable VP6-tagged IBAV

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A reverse genetics system for Ibaraki virus (IBAV) was developed.

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The RG system was used to produce viable VP6-tagged IBAV.

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A region of VP6 (aa 34–82) is not required for IBAV replication in tissue culture.

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The insertion of tags into the nonessential VP6 region did not disrupt replication.

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IBAV VP6 quickly assembled into puncta in the cytosol of infected cells.

Ibaraki virus (IBAV) is a member of the epizootic hemorrhagic disease virus (EHDV) serogroup, which belongs to the Orbivirus genus of the Reoviridae family. Although EHDV, including IBAV, represents an ongoing threat to livestock in the world, molecular mechanisms of EHDV replication and pathogenesis have been unclear. The reverse genetics (RG) system is one of the strong tools to understand molecular mechanisms of virus replication. Here, we developed a RG system for IBAV to identify the nonessential region of a minor structural protein, VP6, by generating VP6-truncated IBAV. Moreover, several tags were inserted into the truncated region to produce VP6-tagged IBAV. We demonstrated that all VP6-tagged IBAV could replicate in BHK cells in the absence of any helper VP6 protein. Further, tagged-VP6 proteins were first assembled into puncta in cells infected with VP6-tagged IBAV. Our data suggests that, in order to initiate primary replication, IBAV VP6 is likely to accumulate in some parts of infected cells to assemble efficiently into the primary replication complex (subcore).

Bovine Arboviruses in Culicoides Biting Midges and Sentinel Cattle in Southern Japan from 2003 to 2013

Epizootic congenital abnormalities, encephalomyelitis and febrile illnesses in cattle caused by arthropod-borne viruses (arboviruses) are prevalent in Japan. Causative viruses including orthobunyaviruses, orbiviruses and rhabdovirus are thought to be transmitted by Culicoides biting midges. Recently, the incursions of several arboviruses, potentially Culicoides-borne, were newly confirmed in Japan. However, their spread pattern and exact vector species are currently uncertain. Attempts to isolate arboviruses from Culicoides biting midges and sentinel cattle were conducted in Kagoshima, located at the southernmost end of the main islands of Japan, a potentially high-risk area for incursion of arboviral diseases and outbreak of endemic ones. Seventy-eight isolates comprising Akabane, Peaton and Sathuperi viruses of the genus Orthobunyavirus of the family Bunyaviridae, bluetongue virus serotype 16, D'Aguilar virus, Bunyip Creek virus and epizootic haemorrhagic disease virus serotype 1 of the genus Orbivirus of the family Reoviridae, a potentially novel rhabdovirus of the genus Ephemerovirus and unidentified orbivirus-like viruses were obtained from Culicoides biting midges and sentinel cattle between 2003 and 2013. Akabane, Sathuperi, D'Aguilar and Bunyip Creek viruses were selectively isolated from Culicoides oxystoma, suggesting this vector's responsibility for these arbovirus outbreaks. The results of virus isolation also implied that C. tainanus, C. jacobsoni and C. punctatus are competent for the transmission of bluetongue virus serotype 16, Peaton virus and epizootic haemorrhagic disease virus serotype 1, respectively. Our monitoring in Culicoides biting midges and sentinel cattle detected the circulation of Akabane virus just prior to the accumulations of bovine congenital abnormalities and encephalomyelitis by it around study sites in 2003, 2006, 2008 and 2013. Silent circulations of the other arboviruses, including potentially new viruses, were also detected during the study period.

Characterization of epizootic hemorrhagic disease virus from a bovine with clinical disease with high nucleotide sequence identity to white-tailed deer isolates

Epizootic hemorrhagic disease virus (EHDV) was isolated from a pregnant cow in Indiana, USA, exhibiting excessive salivation, pyrexia and abortion. VP2, VP5, and VP7 sequences of the isolated bovine EHDV showed 97.7, 97.4, and 97.9 % identity to a serotype 2 reference virus. Bovine EHDV was closely related (>99.9 %) to white tailed deer (WTD) EHDV collected from Iowa in 2013 and showed less than 2.1 % divergence from EHDV collected from WTD across the USA in 2013. The high degree of sequence identity between bovine and WTD EHDV isolates demonstrates that similar viruses concurrently circulate in both species and suggests possible further incursions into bovines.

[Reverse genetics systems for orbiviruses reveal the essential mechanisms in their replication]

The members of Orbivirus genus within the family Reoviridae cause severe arthropod-born diseases mainly in ruminants and equids. In addition, the orbiviruses, which can infect humans, have been reported. In the last decade, the molecular and structural studies for orbiviruses, including Bluetongue virus (BTV), has made a great progress. Especially, a reverse genetics system (RG) for BTV, developed soon after Orhoreovirus and Rotavirus, is a major breakthrough. Here, I introduced the recent findings in orbivirus replication, especially the function of an enzymatic protein, VP6.

Epizootic hemorrhagic disease virus serotype 6 experimentation on adult cattle

Epizootic hemorrhagic disease virus (EHDV), an arthropod-borne orbivirus (family Reoviridae), is an emerging pathogen of wild and domestic ruminants closely related to bluetongue virus (BTV). EHDV serotype 6 (EHDV6) has recently caused outbreaks close to Europe in Turkey and Morocco and a recent experimental study performed on calves inoculated with these two EHDV6 strains showed that the young animals have remained clinically unaffected. The aim of this study was to investigate the pathogenicity of an EHDV6 strain from La Reunion Island in adult Holstein (18-month-old heifers). This EHDV6 strain has induced clinical signs in cattle in the field. Samples taken throughout the study were tested with commercially available ELISA and real-time RT-PCR kits. Very mild clinical manifestations were observed in cattle during the experiment although high levels of viral RNA and virus were found in their blood. EHDV was isolated from the blood of infected animals at 8 dpi. Antibodies against EHDV were first detected by 7 dpi and persisted up to the end of the study. Virus was detected in various tissue samples until 35 dpi, but was not infectious. In view of the recent circulation of different arboviruses in Europe, this study demonstrates what the EHD induces a strong viraemia in adult Holstein cattle and shows that a spread of EHD on European livestock cattle is possible.

Epizootic hemorrhagic disease in yaks (Bos grunniens)

An epizootic of hemorrhagic disease associated with Epizootic hemorrhagic disease virus serotype 2 (EHDV-2) infections in yaks from 5 herds occurred in Colorado between August 21 and October 3, 2012. Affected yaks presented with fever, lethargy, anorexia, dyspnea, and swollen conjunctivae. Ulcerated dental pads, mucoid sanguineous nasal discharge, petechial hemorrhages in multiple organs, pulmonary edema, and serosanguinous fluid in the thorax, abdomen, and pericardial sac were observed at necropsy. Blood and tissue samples from 8 yaks with similar clinical signs and necropsy findings were positive for EHDV-2 by reverse transcription polymerase chain reaction and 5 yaks were seropositive for EHDV. Tests for malignant catarrhal fever ( Ovine herpesvirus 2), Bovine viral diarrhea virus, Bovine herpesvirus 1, Foot-and-mouth disease virus, and Vesicular stomatitis virus were negative. The findings indicate that yaks are susceptible to infection with EHDV-2 and exhibit the clinical signs, and gross and histologic lesions of hemorrhagic disease observed in other ruminant species.

Epizootic heamorragic disease

Epizootic haemorrhagic disease (EHD) is an infectious non-contagious viral disease transmitted by insects of the genus Culicoides which affects wild and domestic ruminants. The causative agent, the epizootic haemorrhagic disease virus (EHDV), belongs to the family Reoviridae, genus Orbivirus and shares many morphological and structural characteristics with the other members of the genus such as bluetongue, African horse sickness and equine encephalosis viruses. In recent years EHD outbreaks have been reported in countries bordering the European Union. They caused disease in cattle and severe repercussion on the livestock industry of the affected countries. In the light of recent European bluetongue epizootic these events pose an increasing threat to the European Union. This review includes the most recent information regarding the virus and the disease as well as tools for its diagnosis and control. It is our conviction that more attention should be drawn to both EHDV and the disease itself in order to fulfil all these gaps and not to be unprepared in case future possible incursions.

Infectious causes of reproductive disorders in cattle

The incidences of reproductive disorders in bovine are increasing over years. This scenario is further aggravating due to more emphasis on selection and rearing of animal for specific commercial purposes which compromises livestock reproduction. Reproductive disorders like infertility and abortions in cattle are major problems in the bovine industry. The reproductive disorders might be caused by several different agents such as physical agents, chemical agents, biological agents, etc. Also, the causative agent and pathogenesis of reproductive disorders are influenced by various factors including environmental factor. The exact causes may not be evident and are often complicated with multiple causative agents. Thus, there is a need for multi-faceted approach to understand correlation of various factors with reproductive performance. Of the agents, infectious biological agents are significant cause of reproductive disorder and are of high priority in the bovine industry. These factors are not only related to the prosperity of bovine industry but are also important from public health point of view because of their zoonotic potentials. Several infectious agents like bacterial, viral, protozoon, chlamydial and fungal agents are known to have direct impact on reproductive health of cattle. These diseases can be arranged and discussed in different groups based on the causative agents.

Isolation of bovine arboviruses from Culicoides biting midges (Diptera: Ceratopogonidae) in southern Japan: 1985--2002

In 1985--2002, surveillance for bovine arboviruses was conducted in Kagoshima, located in the most southern part of the main islands of Japan and known to be an area where bovine arboviral diseases have frequently been epidemic. Culicoides biting midges were collected in a cowshed by light traps. A total of 456,300 Culicoides biting midges representing 13 species were collected, and a portion of each pool of midges were tested for virus isolation. Overall, 85 isolates of six different viruses were obtained from the collected midges. The isolated viruses included two Orthobunyaviruses, Akabane and Aino viruses; three Orbiviruses, Chuzan, D'Aguliar, and Ibaraki viruses; and one unclassified virus, a bunyavirus-like virus. The viruses were most frequently isolated from Culicoides oxystoma Kieffer (85.9% of 85 isolates). Isolations of all viruses except for the bunyavirus-like virus were made from this species. Our data indicated that C. oxystoma is a potential vector for bovine arboviruses in southern Japan.

Simultaneous detection of bovine arboviruses using single-tube multiplex reverse transcription-polymerase chain reaction

Single-tube multiplex reverse transcription-polymerase chain reaction (mRT-PCR) assay was developed to detect and identify arboviruses in infected cell-culture fluids and field specimens. The technique was equally sensitive for detecting five different viruses in cell cultures, namely the Chuzan, Ibaraki, and Bluetongue viruses belonging to Orbivirus, and the Akabane virus and Peaton virus belonging to Orthobunyavirus, and was less sensitive than former viruses for detecting Aino virus belonging to Orthobunyavirus. The mRT-PCR reliably detected 0.6-10(3.1) median tissue culture infective doses. The mRT-PCR readily identified viruses by discriminating the size of their amplified gene products. The technique was as sensitive as virus isolation in detecting single infected plasma in five plasmas from sentinel cattle and in detecting two infectious homogenates in eight homogenates of Culicoides biting midges. The mRT-PCR may be a sensitive and rapid assay for surveillance of bovine arboviruses in field specimens.

Differences in Ibaraki virus RNA segment 3 sequences from three epidemics

Phylogenetic tree and partial nucleotide sequence analysis of RNA segment 3 were conducted to compare the Ibaraki virus (IBAV) strains from three epidemics in Japan, and serotype 2 epizootic hemorrhagic disease virus strains isolated in Australia, Taiwan, and Canada. Each strain was classified relative to the Ibaraki disease (IBAD) epidemics, which occurred in 1959-1960, 1987, or 1997-1998. In particular, major variation of the gene was identified in the strains isolated after 1997 when a new type of IBAD with the abnormal birth was confirmed. Ibaraki viruses isolated in Japan were more closely related to Taiwanese and Australian strains based on genetics, while the Canadian strain was more distantly related.

Replication of bluetongue virus and epizootic hemorrhagic disease virus in pulmonary artery endothelial cells obtained from cattle, sheep, and deer

OBJECTIVE

To compare replication of bluetongue virus (BTV) and epizootic hemorrhagic disease virus (EHDV) in pulmonary artery endothelial cells (ECs) obtained from juvenile cattle, sheep, white-tailed deer (WTD; Odocoileus virginianus), and black-tailed deer (BTD; O hemionus columbianus).

SAMPLE POPULATION

Cultures of pulmonary artery ECs obtained from 3 cattle, 3 sheep, 3 WTD, and 1 BTD.

PROCEDURE

Purified cultures of pulmonary artery ECs were established. Replication, incidence of infection, and cytopathic effects of prototype strains of BTV serotype 17 (BTV-17) and 2 serotypes of EHDV (EHDV-1), and (EHDV-2) were compared in replicate cultures of ECs from each of the 4 ruminant species by use of virus titration and flow cytometric analysis.

RESULTS

All 3 viruses replicated in ECs from the 4 ruminant species; however, BTV-17 replicated more rapidly than did either serotype of EHDV. Each virus replicated to a high titer in all ECs, although titers of EHDV-1 were significantly lower in sheep ECs than in ECs of other species. Furthermore, all viruses caused extensive cytopathic effects and a high incidence of cellular infection; however, incidence of cellular infection and cytopathic effects were significantly lower in EHDV-1-infected sheep ECs and EHDV-2-infected BTD ECs.

CONCLUSIONS AND CLINICAL RELEVANCE

There were only minor differences in replication, incidence of infection, and cytopathic effects for BTV-17, EHDV-1, or EHDV-2 in ECs of cattle, sheep, BTD, and WTD. It is not likely that differences in expression of disease in BTV- and EHDV-infected ruminants are attributable only to species-specific differences in the susceptibility of ECs to infection with the 2 orbiviruses.

Analysis of intratypic variation evident in an Ibaraki virus strain and its epizootic hemorrhagic disease virus serogroup

A new strain of Ibaraki virus (IBAV) was isolated from cattle showing atypical symptoms of Ibaraki disease. The isolate was genetically characterized, and the genetic diversity and evolution of the capsid proteins of viruses in the epizootic hemorrhagic disease virus (EHDV) serogroup were investigated. The nucleotide sequences of the isolate's viral RNA segments 2, 3, 6, and 7, which encode the viral structural proteins VP2, VP3, VP5, and VP7, respectively, were determined and were then compared against those of the existing strains of IBAV and EHDV, to which IBAV belongs serologically. The nucleotide sequences of segments 3 and 7 were conserved within the EHDV serogroup, particularly well among the strains of IBAV and Australian EHDV. The similarity of the sequence of segment 6 of the isolate to sequences of corresponding segments of the other strains of IBAV and EHDV was found to be about 93%. The similarity of segment 2 of the isolate to segments 2 of the other strains of IBAV and EHDV was less than 70%. Phylogenetic analysis based on the deduced amino acid sequences of segments 3 and 7 revealed that the viruses differed according to their geographical distributions. However, the new isolate of IBAV was categorized as having a distinct lineage in the phylogenetic tree of VP2. These results suggest that the isolate was modified by a reassortment of segment 2 and that it exhibits unique genetic and antigenic characteristics.