Schmallenberg virus-two years of experiences

The first report of schmallenberg virus seroprevalence and associated risk factors in cattles in northern Algeria

Schmallenberg virus (SBV) is an arbovirus belonging to the Peribunyaviridae family. It is spread by many biting midges of Culicoides spp genus. In cattle, SBV infection can lead to sporadic abortions, as well as significant reproductive issues, including congenital malformations in newborns and stillbirths. Our study aimed to assess the seroprevalence of schmallenberg virus infection in cattles using indirect ELISA test, and identifying related risk factors. A total of 370 blood samples were randomly collected from cattles of six districts in north Algeria (Algiers, Blida, Bouira, Boumerdès, Tipaza, and Tizi Ouzou). A questionnaire was performed in order to collect zootechnical parameters data, clinical signs, and geographic location. A seroprevalence of 44% (CI95%, 39 - 49.2%) was revealed. Univariate analyses and multivariate logistic regression were used to assess related risk factors with SBV infection. The findings showed that animals older than 2 years, those in the third stage of pregnancy, and cattle exhibiting symptoms like diarrhea had the highest rates of SBV infection. This study demonstrated that the Schmallenberg virus is endemic in cattle within the investigated region. Effective control of arboviruses is vital for both public health and animal health. To enhance vector disease management for SBV and reduce the risk of its spread to non-endemic regions in Algeria, it is important to establish entomological surveillance as soon as possible.

More than a decade of research on Schmallenberg virus-Knowns and unknowns

Schmallenberg virus, an arbovirus of the Orthobunyavirus genus that primarily infects ruminants, emerged in 2011 near the Dutch-German border region and subsequently caused a large number of abortions and the births of severely malformed newborns in the European livestock population. Immediate intensive research led to the development of reliable diagnostic tests, the identification of competent Culicoides vector species, and the elucidation of the pathogenesis in infected vertebrate hosts. In addition, the structure of the major antigenic domain has been elucidated in great detail, leading to the development of effective marker vaccine candidates. The knowledge gained over the last decade on the biology and pathogenesis of SBV and the experience acquired in its control will be of great value in the future for the control of any similar emerging pathogen of veterinary or public health importance such as Shuni or Oropouche virus. However, some important knowledge gaps remain, for example, the factors contributing to the highly variable transmission rate from dam to fetus or the viral factors responsible for the vector competence of Culicoides midges are largely unknown. Thus, questions still remain for the next decade of research on SBV and related viruses.

Exposure of small ruminants to the Schmallenberg arbovirus in Germany from 2017 to 2018 - animal-specific and flock-management-related risk factors

The Schmallenberg virus (SBV), an emerging Orthobunyavirus of mainly ruminant hosts, caused a substantial epidemic in European ruminant populations between 2011 and 2013. The pathogen is transmitted by arthropod vectors (Culicoides spp.) and can cause reproductive disorders and severe malformations of the offspring or stillbirth. The present study aimed to assess SBV seroprevalence among German sheep and goats a few years after the first virus detection in the country (November 2011). In addition, an extensive risk factor analysis including host-specific and husbandry-related factors was implemented. Seroprevalence was determined by examining serum samples from 2759 sheep and 446 goats out of a total of 70 flocks across five German federal states. The samples were withdrawn in the period between 2017 and 2018. Using a commercial competitive ELISA, antibodies against SBV were detected in all 70 investigated flocks. A percentage of 60.1 % (1657/2759) of the sheep and 40.4 % (180/446) of the goat sera contained SBV antibodies. Generalized linear mixed modeling revealed significant effects of host species (sheep > goats), age (old > young) and sex (female > male) on SBV seroprevalence. For both species, also the farming purpose, and for goats, ectoparasite treatment and the presence of cattle on the farm played a role in terms of risk for SBV exposure. The observations from this study still emphasize a wide distribution of the pathogen in Germany. Nevertheless, the observed seroprevalence might not be sufficient to achieve effective herd immunity. Pinpointing risk factors identified susceptible populations for targeted vaccination programs to reduce potential animal losses caused by SBV.

Characterization of a natural 'dead-end' variant of Schmallenberg virus

Schmallenberg virus (SBV) belongs to the Simbu serogroup within the family Peribunyaviridae, genus Orthobunyavirus and is transmitted by Culicoides biting midges. Infection of naïve ruminants in a critical phase of gestation may lead to severe congenital malformations. Sequence analysis from viremic animals revealed a very high genome stability. In contrast, sequence variations are frequently described for SBV from malformed fetuses. In addition to S segment mutations, especially within the M segment encoding the major immunogen Gc, point mutations or genomic deletions are also observed. Analysis of the SBV_D281/12 isolate from a malformed fetus revealed multiple point mutations in all three genome segments. It also has a large genomic deletion in the antigenic domain encoded by the M segment compared to the original SBV reference strain 'BH80/11' isolated from viremic blood in 2011. Interestingly, SBV_D281/12 showed a marked replication deficiency in vitro in Culicoides sonorensis cells (KC cells), but not in standard baby hamster kidney cells (BHK-21). We therefore generated a set of chimeric viruses of rSBV_D281/12 and wild-type rSBV_BH80/11 by reverse genetics, which were characterized in both KC and BHK-21 cells. It could be shown that the S segment of SBV_D281/12 is responsible for the replication deficit and that it acts independently from the large deletion within Gc. In addition, a single point mutation at position 111 (S to N) of the nucleoprotein was identified as the critical mutation. Our results suggest that virus variants found in malformed fetuses and carrying characteristic genomic mutations may have a clear 'loss of fitness' for their insect hosts in vitro. It can also be concluded that such mutations lead to virus variants that are no longer part of the natural transmission cycle between mammalian and insect hosts. Interestingly, analysis of a series of SBV sequences confirmed the S111N mutation exclusively in samples of malformed fetuses and not in blood from viremic animals. The characterization of these changes will allow the definition of protein functions that are critical for only one group of hosts.

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.

A serological screening for potential viral pathogens among semi-domesticated Eurasian tundra reindeer (Rangifer tarandus tarandus) in Finland

BACKGROUND

Reindeer herding and husbandry is a traditional and important livelihood in Fennoscandia, and about 200,000 semi-domesticated reindeer are herded in Finland. Climatic changes, leading to ice-locked winter pastures, and encroachment of pasture-land have led to changes in reindeer husbandry, increasing the extent of supplementary or full ration feeding, which has become very common in Finland. Keeping reindeer in corrals or gathering them at permanent feeding sites will increase nose-to-nose contact between animals and they may be exposed to poor hygienic conditions. This may impact the epidemiology of infectious diseases, such as viral infections. The aim of this study was to investigate Finnish semi-domesticated reindeer for exposure to viral pathogens. Blood samples were collected from 596 reindeer (358 calves, 238 adults) in 2015, from nine reindeer slaughterhouses, representing most of the reindeer herding regions in Finland. Plasma samples were investigated for antibodies against a selection of known and potential reindeer viral pathogens by using enzyme linked immunosorbent assays (ELISA).

RESULTS

The screening suggested that alphaherpesvirus and gammaherpesvirus (malignant catarrhal fever virus group; MCFV) were enzootic in the reindeer population, with a seroprevalence of 46.5% (range at slaughterhouse level 28.6-64.3%) and 29.0% (range 3.5-62.2%), respectively. Whereas the seroprevalence was significantly higher for alphaherpesvirus among adult reindeer (91.2%) as compared to calves (16.8%), no age difference was revealed for antibodies against gammaherpesvirus. For alphaherpesvirus, the seroprevalence in the northernmost region, having the highest animal density (animals/km2), was significantly higher (55.6%) as compared to the southernmost region (36.2%), whereas the seroprevalence pattern for gammaherpesvirus indicated the opposite, with 8.1% in the north and 50.0% in the south. Four reindeer (0.7%) had antibodies against Pestivirus, whereas no antibodies were detected against Bluetongue virus or Schmallenbergvirus.

CONCLUSIONS

Alphaherpesvirus and gammaherpesvirus (MCFV) seems to be enzootic in the Finnish reindeer population, similar to other reindeer herds in Fennoscandia, whereas the exposure to Pestivirus was low compared to findings in Norway and Sweden. The ongoing changes in the reindeer herding industry necessitate knowledge on reindeer health and diseases that may impact animal welfare and health of reindeer as well as the economy of the reindeer herding industry.

Vaccine development against Schmallenberg virus: from classical inactivated to modified-live to scaffold particle vaccines

BACKGROUND

Subsequent to its first detection in 2011, the insect-transmitted bunyavirus Schmallenberg virus (SBV; genus Orthobunyavirus) caused a large-scale epizootic of fetal malformation in the European ruminant population. By now, SBV established an enzootic status in Central Europe with regular wave-like re-emergence, which has prompted intensive research efforts in order to elucidate the pathogenesis and to develop countermeasures. Since different orthobunyaviruses share a very similar structural organization, SBV has become an important model virus to study orthobunyaviruses in general and for the development of vaccines. In this review article, we summarize which vaccine formulations have been tested to prevent SBV infections in livestock animals. MAIN: In a first step, inactivated SBV candidate vaccines were developed, which efficiently protected against an experimental SBV infection. Due to the inability to differentiate infected from vaccinated animals (= DIVA capability), a series of further approaches ranging from modified live, live-vectored, subunit and DNA-mediated vaccine delivery to multimeric antigen-presentation on scaffold particles was developed and evaluated. In short, it was repeatedly demonstrated that the N-terminal half of the glycoprotein Gc, composed of the Gc head and the head-stalk, is highly immunogenic, with a superior immunogenicity of the complete head-stalk domain compared to the Gc head only. Furthermore, in all Gc protein-based vaccine candidates, immunized animals can be readily discriminated from animals infected with the field virus by the absence of antibodies against the viral N-protein.

CONCLUSIONS

Using SBV as a model virus, several vaccination-challenge studies in target species underscored the superior performance of antigenic domains compared to linear epitopes regarding their immunogenicity. In addition, it could be shown that holistic approaches combining immunization-challenge infection studies with structural analyses provide essential knowledge required for an improved vaccine design.

A Screening for Virus Infections in Eight Herds of Semi-domesticated Eurasian Tundra Reindeer (Rangifer tarandus tarandus) in Norway, 2013-2018

Background: Previous serological screenings have indicated that Eurasian semi-domesticated tundra reindeer (Rangifer tarandus tarandus) in Finnmark, Northern Norway, are exposed to alphaherpesvirus, gammaherpesvirus and pestivirus. Alphaherpesvirus (i.e., Cervid herpesvirus 2; CvHV2) has been identified as the transmissible component of infectious keratoconjunctivitis (IKC). Limited knowledge exists on the presence and prevalence of virus infections in other herding regions in Norway, which are hosting ~67,000 semi-domesticated reindeer and have contact with other species and populations of wildlife and livestock than those present in Finnmark. Methods: Blood samples (n = 618) were obtained over five winter seasons (2013-2018), from eight different herds representing summer pasture districts in Tana, Lakselv, Tromsø, Lødingen, Hattfjelldal, Fosen, Røros, and Filefjell, distributed from North to South of the reindeer herding regions in Norway. Blood samples were investigated for specific antibodies against five viral pathogen groups, alphaherpesvirus, gammaherpesvirus (viruses in the malignant catarrhal fever group; MCFV), pestivirus, bluetongue virus (BTV), and Schmallenberg virus (SBV), by using commercial multispecies serological tests (ELISA). In addition, swab samples obtained from the nasal mucosal membrane from 486 reindeer were investigated by PCR for parapoxvirus-specific DNA. Results: Antibodies against aphaherpesvirus and MCFV were found in all eight herds, with a total prevalence of 42% (range 21-62%) and 11% (range 2-15%), respectively. Anti-Pestivirus antibodies were detected in five of eight herds, with a total prevalence of 19% (range 0-52%), with two of the herds having a particularly high seroprevalence. Antibodies against BTV or SBV were not detected in any of the animals. Parapoxvirus-specific DNA was detected in two animals representing two different herds in Finnmark. Conclusions: This study confirmed that alphaherpesvirus and MCFV are enzootic throughout the geographical reindeer herding regions in Norway, and that pestivirus is present in most of the herds, with varying seroprevalence. No exposure to BTV and SBV was evident. This study also indicated that semi-domesticated reindeer in Finnmark are exposed to parapoxvirus without disease outbreaks being reported from this region.

Development of a Modular Vaccine Platform for Multimeric Antigen Display Using an Orthobunyavirus Model

Emerging infectious diseases represent an increasing threat to human and animal health. Therefore, safe and effective vaccines that could be available within a short time frame after an outbreak are required for adequate prevention and control. Here, we developed a robust and versatile self-assembling multimeric protein scaffold particle (MPSP) vaccine platform using lumazine synthase (LS) from Aquifex aeolicus. This scaffold allowed the presentation of peptide epitopes by genetic fusion as well as the presentation of large antigens by bacterial superglue-based conjugation to the pre-assembled particle. Using the orthobunyavirus model Schmallenberg virus (SBV) we designed MPSPs presenting major immunogens of SBV and assessed their efficacy in a mouse model as well as in cattle, a target species of SBV. All prototype vaccines conferred protection from viral challenge infection and the multivalent presentation of the selected antigens on the MPSP markedly improved their immunogenicity compared to the monomeric subunits. Even a single shot vaccination protected about 80% of mice from an otherwise lethal dose of SBV. Most importantly, the MPSPs induced a virtually sterile immunity in cattle. Altogether, LS represents a promising platform for modular and rapid vaccine design.

A novel Schmallenberg virus subunit vaccine candidate protects IFNAR-/- mice against virulent SBV challenge

Schmallenberg virus (SBV), an arthropod-transmitted pathogenic bunyavirus, continues to be a threat to the European livestock industry, causing morbidity and mortality among young ruminant livestock. Here, we describe a novel SBV subunit vaccine, based on bacterially expressed SBV nucleoprotein (SBV-N) administered with a veterinary-grade Saponin adjuvant. When assayed in an IFNAR^-/- mouse model, SBV-N with Saponin induced strong non-neutralizing broadly virus-reactive antibodies, decreased clinical signs, as well as significantly reduced viremia. Vaccination assays also suggest that this level of immune protection is cell mediated, as evidenced by the lack of neutralizing antibodies, as well as interferon-γ secretion observed in vitro. Therefore, based on these results, bacterially expressed SBV-N, co-administered with veterinary-grade Saponin adjuvant may serve as a promising economical alternative to current SBV vaccines, and warrant further evaluation in large ruminant animal models. Moreover, we propose that this strategy may be applicable to other bunyaviruses.

Towards modernizing the taxonomy of Mediterranean Culicoides using classical morphology, mtDNA barcoding, and MALDI-TOF MS protein profiling

Culicoides biting midges (Diptera: Ceratopogonidae) are a highly successful group of small (1-3 mm) hematophagous flies, infamous for the role they play as biological vectors for numerous pathogens of veterinary significance. The principal aim of the national animal disease surveillance program of Israel is to be able to rapidly sort and identify live field-captured insects including Culicoides for arbovirus screening. In this exploratory study, three identification methods-classical morphology, DNA barcoding, and MALDI-TOF MS-were applied simultaneously to individuals of 10 Culicoides species that commonly attack livestock in Israel. The strengths and limitations of the three methods are compared and evaluated. In essence, the CO1 barcoding and MALDI-TOF MS results closely matched those of classical morphology. Furthermore, at a higher level and in strong accordance with recognized subgenera, the 10 species, in the reconstructed phylogenies, coalesced into multiple deeper-branched monophyletic clades. However, some discrepancies between the molecular and protein profiling results did occur and proved difficult to assess in terms of taxonomic significance. This difficulty underscores how tricky it is to establish clear species limits when methods involving borderline cutoff values and similarity indices are used as a taxonomic aid. An added shortcoming of the pluralistic triple-method approach is that a significant percentage of the species-level depositions in the GenBank and BOLD databases are misidentified, hindering structured comparison and interpretation of the morphological and molecular results obtained. Aspects of the unresolved taxonomy of various biting midge assemblages within the Mediterranean basin, including minor changes to the Israeli Culicoides checklist, are discussed in light of the methods applied. It is observed that the direct access that classical morphology provides to the external environment (or species niche) is indispensable to the full and correct interpretation (and application) of concomitant molecular and protein profiling results. The Culicoides taxonomy of the future ought to be fully integrative, during which the assimilation of modern methodological advances should strengthen-rather than undermine-the morphological foundations laid down during the 260-year Linnaean epoch.

Epidemiological surveillance of Schmallenberg virus in small ruminants in southern Spain

Schmallenberg virus (SBV) is an emerging Culicoides-borne Orthobunyavirus that affects ruminant species. Between 2011 and 2013, it was responsible for a large-scale epidemic in Europe. In the present study, we aimed to determine the seroprevalence, spatial distribution and risk factors associated with SBV exposure in sheep and goats in the region where the first Schmallenberg disease outbreak in Spain was reported. Blood samples from 1,796 small ruminants from 120 farms were collected in Andalusia (southern Spain) between 2015 and 2017. Antibodies against SBV were detected in 536 of 1,796 animals (29.8%; 95%CI: 27.7-32.0) using a commercial blocking ELISA. The individual seroprevalence according to species was 31.1% (280/900; 95%CI: 28.1-34.1) in sheep and 28.6% (256/896; 95%CI: 25.6-31.5) in goats. The farm prevalence was 76.7% (95%CI: 69.1-84.2). Seropositivity to SBV was confirmed in both sheep and goats in all provinces by virus neutralization test. Two significant (p < .001) spatial clusters of high seroprevalence were identified. The generalized estimating equation analysis showed that management system (extensive), temperature (>14ºC) and altitude (<400 metres above sea level) were risk factors associated with SBV exposure in small ruminants. Our results highlight widespread but not homogeneous circulation of SBV in small ruminant populations in Spain.

A Genome-Wide CRISPR-Cas9 Screen Reveals the Requirement of Host Cell Sulfation for Schmallenberg Virus Infection

Schmallenberg virus (SBV) is an insect-transmitted orthobunyavirus that can cause abortions and congenital malformations in the offspring of ruminants. Even though the two viral surface glycoproteins Gn and Gc are involved in host cell entry, the specific cellular receptors of SBV are currently unknown. Using genome-wide CRISPR-Cas9 forward screening, we identified 3'-phosphoadenosine 5'-phosphosulfate (PAPS) transporter 1 (PAPST1) as an essential factor for SBV infection. PAPST1 is a sulfotransferase involved in heparan sulfate proteoglycan synthesis encoded by the solute carrier family 35 member B2 gene (SLC35B2). SBV cell surface attachment and entry were largely reduced upon the knockout of SLC35B2, whereas the reconstitution of SLC35B2 in these cells fully restored their susceptibility to SBV infection. Furthermore, treatment of cells with heparinase diminished infection with SBV, confirming that heparan sulfate plays an important role in cell attachment and entry, although to various degrees, heparan sulfate was also found to be important to initiate infection by two other bunyaviruses, La Crosse virus and Rift Valley fever virus. Thus, PAPST1-triggered synthesis of cell surface heparan sulfate is required for the efficient replication of SBV and other bunyaviruses.IMPORTANCE SBV is a newly emerging orthobunyavirus (family Peribunyaviridae) that has spread rapidly across Europe since 2011, resulting in substantial economic losses in livestock farming. In this study, we performed unbiased genome-wide CRISPR-Cas9 screening and identified PAPST1, a sulfotransferase encoded by SLC35B2, as a host entry factor for SBV. Consistent with its role in the synthesis of heparan sulfate, we show that this activity is required for efficient infection by SBV. A comparable dependency on heparan sulfate was also observed for La Crosse virus and Rift Valley fever virus, highlighting the importance of heparan sulfate for host cell infection by bunyaviruses. Thus, the present work provides crucial insights into virus-host interactions of important animal and human pathogens.

Schmallenberg Virus: To Vaccinate, or Not to Vaccinate?

Schmallenberg virus (SBV), a teratogenic orthobunyavirus that infects predominantly ruminants, emerged in 2011 in Central Europe, spread rapidly throughout the continent, and subsequently established an endemic status with re-circulations to a larger extent every 2 to 3 years. Hence, it represents a constant threat to the continent's ruminant population when no effective countermeasures are implemented. Here, we discuss potential preventive measures to protect from Schmallenberg disease. Previous experiences with other arboviruses like bluetongue virus have already demonstrated that vaccination of livestock against a vector-transmitted disease can play a major role in reducing or even stopping virus circulation. For SBV, specific inactivated whole-virus vaccines have been developed and marketing authorizations were granted for such preparations. In addition, candidate marker vaccines either as live attenuated, DNA-mediated, subunit or live-vectored preparations have been developed, but none of these DIVA-capable candidate vaccines are currently commercially available. At the moment, the licensed inactivated vaccines are used only to a very limited extent. The high seroprevalence rates induced in years of virus re-occurrence to a larger extent, the wave-like and sometimes hard to predict circulation pattern of SBV, and the expenditures of time and costs for the vaccinations presumably impact on the willingness to vaccinate. However, one should bear in mind that the consequence of seronegative young animals and regular renewed virus circulation might be again more cases of fetal malformation caused by an infection of naïve dams during one of their first gestations. Therefore, an appropriate and cost-effective strategy might be to vaccinate naïve female animals of all affected species before the reproductive age.

Re-circulation of Schmallenberg virus, Germany, 2019

Schmallenberg virus (SBV), an insect-transmitted orthobunyavirus that induces severe foetal malformation in calves and lambs, was detected for the first time in late summer 2011 in Central Europe. Thereafter, the virus spread rapidly across the continent causing a large epidemic in the ruminant population. In 2019, detection of virus was again reported more frequently in Germany. From March to November, infections of viremic adult animals were noticed. In September, SBV genome was also detected in newborn lambs. Altogether, affected species included cattle, sheep, a goat and a fallow deer. M-segment sequences were generated from viruses detected in viremic cattle and compared to viral sequences from previous years. The genome of viruses detected in the blood of acutely infected adult cattle and sheep, which represent the circulating SBV strains, seems very stable over the course of nine years and in various European countries. The nucleotide similarities of these viruses are as high as 99.4%-100%. The renewed SBV circulation in 2019 in the country, in which the virus was first detected in 2011 and where it circulated again in 2014 and 2016, suggests the establishment of an enzootic status in Central Europe with regular larger waves in a cycle of around 3 years. Therefore, it has to be anticipated that SBV will re-emerge at similar intervals in future, and hence, it represents a constant threat for the continent's ruminant population.

Elongin C Contributes to RNA Polymerase II Degradation by the Interferon Antagonist NSs of La Crosse Orthobunyavirus

The mosquito-borne La Crosse virus (LACV; genus Orthobunyavirus, family Peribunyaviridae, order Bunyavirales) is prevalent in the United States and can cause severe childhood meningoencephalitis. Its main virulence factor, the nonstructural protein NSs, is a strong inhibitor of the antiviral type I interferon (IFN) system. NSs acts by imposing a global host mRNA synthesis shutoff, mediated by NSs-driven proteasomal degradation of the RPB1 subunit of RNA polymerase II. Here, we show that RPB1 degradation commences as early as 1 h postinfection, and identify the E3 ubiquitin ligase subunit Elongin C (and its binding partners Elongins A and B) as an NSs cofactor involved in RPB1 degradation and in suppression of global as well as IFN-related mRNA synthesis.

Mosquito-borne La Crosse virus (LACV; genus Orthobunyavirus, family Peribunyaviridae, order Bunyavirales) causes up to 100 annual cases of severe meningoencephalitis in children and young adults in the United States. A major virulence factor of LACV is the nonstructural protein NSs, which inhibits host cell mRNA synthesis to prevent the induction of antiviral type I interferons (IFN-α/β). To achieve this host transcriptional shutoff, LACV NSs drives the proteasomal degradation of RPB1, the large subunit of mammalian RNA polymerase II. Here, we show that NSs acts in a surprisingly rapid manner, as RPB1 degradation was commencing already at 1 h postinfection. The RPB1 degradation was partially dependent on the cellular E3 ubiquitin ligase subunit Elongin C. Consequently, removal of Elongin C, but also of the subunits Elongin A or B by siRNA transfection partially rescued general RNAP II transcription and IFN-beta mRNA synthesis from the blockade by NSs. In line with these results, LACV NSs was found to trigger the redistribution of Elongin C out of nucleolar speckles, which, however, is an epiphenomenon rather than part of the NSs mechanism. Our study also shows that the molecular phenotype of LACV NSs is different from RNA polymerase II inhibitors like α-amanitin or Rift Valley fever virus NSs, indicating that LACV is unique in involving the Elongin complex to shut off host transcription and IFN response.

IMPORTANCE The mosquito-borne La Crosse virus (LACV; genus Orthobunyavirus, family Peribunyaviridae, order Bunyavirales) is prevalent in the United States and can cause severe childhood meningoencephalitis. Its main virulence factor, the nonstructural protein NSs, is a strong inhibitor of the antiviral type I interferon (IFN) system. NSs acts by imposing a global host mRNA synthesis shutoff, mediated by NSs-driven proteasomal degradation of the RPB1 subunit of RNA polymerase II. Here, we show that RPB1 degradation commences as early as 1 h postinfection, and identify the E3 ubiquitin ligase subunit Elongin C (and its binding partners Elongins A and B) as an NSs cofactor involved in RPB1 degradation and in suppression of global as well as IFN-related mRNA synthesis.

Low incidence of Schmallenberg virus infection in natural cases of abortion in domestic ruminants in Hungary

An epizootic caused by a new orthobunyavirus called Schmallenberg virus (SBV) was recognised in European ruminants in 2011 and 2012. The re-emergence of the infection was reported in several countries in the subsequent years. Although the main clinical sign of SBV infection is abortion, the impact of SBV in natural cases of abortion in domestic ruminants had not been systematically examined before this study. The aim of the study was to investigate the role of SBV infection and to compare it to the importance of other causes of abortion by examining 537 natural cases of abortion that had occurred between 2011 and 2017 in Hungary. The cause of abortion was determined in 165 (31%) cases. An infectious cause was proved in 88 (16%) cases. SBV infection was found only in a total of four cases (0.8%) using real-time polymerase chain reaction. Three of them proved to be inapparent SBV infection, and one case was attributed to SBV-induced abortion by detecting non-purulent encephalitis and SBV nucleoprotein by immunohistochemistry in a brain tissue sample. According to the results, SBV played a minor role in natural cases of domestic ruminant abortion in Hungary during the 7-year period following the first SBV outbreak in 2011.

Seasonal and spatial variation in Culicoides community structure and their potential role in transmitting Simbu serogroup viruses in Israel

Culicoides biting midges (Diptera: Ceratopogonidae) are a successful group of small (1-3 mm) haematophagous flies, some species of which are biological vectors of veterinary arboviruses, such as bluetongue virus, epizootic haemorrhagic disease virus, African horse sickness virus and Simbu serogroup viruses. In this study, we examine seasonal and spatial effects on the presence and distribution of Culicoides communities associated with ruminant and equine farms in Israel, and their infection with Simbu serogroup viruses. Our results demonstrate that both the vectors and the viruses are widely spread in Israel, including regions that were previously considered Culicoides-free. Moreover, our results show that although seasonality affects infection with Simbu serogroup viruses, both viruses and potential vectors can be found year round, suggesting continuous circulation of Simbu serogroup viruses in Israeli livestock farms. Finally, this study provides novel and basic information on Simbu serogroup-infected Culicoides in Israel: it demonstrates that Sathuperi, Shuni and Peaton viruses were circulating in Israel in 2015-2017 as they were found in C. imicola and C. oxystoma, both potential vectors of these viruses, and supplies the first-ever genomic detection of Sathuperi in Israel. Consequently, the data emerging from this study are of importance in understanding the epidemiology of arboviruses in Israel and are of relevance to the potential spread and possible future outbreaks of different Simbu serogroup viruses within the Mediterranean region and Europe.

A Multi-Pathogen Screening of Captive Reindeer (Rangifer tarandus) in Germany Based on Serological and Molecular Assays

Captive reindeer in German zoos and wildlife parks live outside their natural geographic range and are exposed to a variety of viral, bacterial and protozoan pathogens, some host-specific and some which they are not exposed to in their native habitat. Reindeer blood samples and ticks collected in 2013 from 123 reindeer at 16 different zoological facilities were available from a previous study. The aims of this study were to assess the serological status of these animals with regards to various microorganisms as well as to test ticks (Ixodes ricinus) and blood samples for the presence of Anaplasma spp. DNA in order to evaluate the exposure of captive reindeer in Germany to a variety of pathogens. A total of 119 or 118 serum samples were screened (ELISA) and antibodies were detected (seropositive/tested, prevalence, confidence interval) against alphaherpesvirus (24/119, 20.3%, CI: 13.9–28.3), bluetongue virus (BTV; 4/119, 3.4%, CI: 1.0–8.7), malignant catarrhal fever related gammaherpesvirus (MCFV-related gammaherpesvirus; 7/119, 5.9%, CI: 2.7–11.9), pestivirus (5/118, 4.2%, CI: 1.6–9.8), Schmallenberg virus (SBV; 70/118, 59.3%, CI: 50.3–67.8), smooth Brucella spp. (1/118; 0.9%, CI: 0–5.1), Neospora caninum (5/118, 4.2%, CI: 1.6–9.8), and Toxoplasma gondii (62/119, 52.1%, CI: 43.2–60.9). These results suggested the exposure of reindeer to all tested pathogens. Moreover, real-time PCR for Anaplasma phagocytophilum targeting the partial msp2 gene was performed on DNA extracted from whole blood samples from reindeer (n = 123) and from ticks (n = 49) collected from 22 reindeer in seven different facilities. In addition to the real-time PCR, a semi-nested PCR for the partial groEL gene, and a nested PCR targeting the partial 16S rRNA gene were performed. DNA of A. phagocytophilum was detected in 17 reindeer (13.8%) and 15 ticks (30.6%). Three of the five reindeer with ticks having A. phagocytophilum DNA also had such DNA in blood. These results indicate that captive reindeer can be exposed to several ruminant pathogens that they hitherto had no known exposure to through their natural geographical distribution and habitats as shown for Culicoides-borne BTV and SBV. Further, captive reindeer may serve as reservoir hosts for pathogens circulating in local domestic, captive, and wild ruminant species and populations and arthropod vectors.

Schmallenberg virus: a systematic international literature review (2011-2019) from an Irish perspective

In Autumn 2011, nonspecific clinical signs of pyrexia, diarrhoea, and drop in milk yield were observed in dairy cattle near the German town of Schmallenberg at the Dutch/German border. Targeted veterinary diagnostic investigations for classical endemic and emerging viruses could not identify a causal agent. Blood samples were collected from animals with clinical signs and subjected to metagenomic analysis; a novel orthobunyavirus was identified and named Schmallenberg virus (SBV). In late 2011/early 2012, an epidemic of abortions and congenital malformations in calves, lambs and goat kids, characterised by arthrogryposis and hydranencephaly were reported in continental Europe. Subsequently, SBV RNA was confirmed in both aborted and congenitally malformed foetuses and also in Culicoides species biting midges. It soon became evident that SBV was an arthropod-borne teratogenic virus affecting domestic ruminants. SBV rapidly achieved a pan-European distribution with most countries confirming SBV infection within a year or two of the initial emergence. The first Irish case of SBV was confirmed in the south of the country in late 2012 in a bovine foetus.

Since SBV was first identified in 2011, a considerable body of scientific research has been conducted internationally describing this novel emerging virus. The aim of this systematic review is to provide a comprehensive synopsis of the most up-to-date scientific literature regarding the origin of SBV and the spread of the Schmallenberg epidemic, in addition to describing the species affected, clinical signs, pathogenesis, transmission, risk factors, impact, diagnostics, surveillance methods and control measures. This review also highlights current knowledge gaps in the scientific literature regarding SBV, most notably the requirement for further research to determine if, and to what extent, SBV circulation occurred in Europe and internationally during 2017 and 2018. Moreover, recommendations are also made regarding future arbovirus surveillance in Europe, specifically the establishment of a European-wide sentinel herd surveillance program, which incorporates bovine serology and Culicoides entomology and virology studies, at national and international level to monitor for the emergence and re-emergence of arboviruses such as SBV, bluetongue virus and other novel Culicoides-borne arboviruses.

Culicoides Biting Midges-Underestimated Vectors for Arboviruses of Public Health and Veterinary Importance

Culicoides biting midges, small hematophagous dipterans, are the demonstrated or putative vectors of multiple arboviruses of veterinary and public health importance. Despite its relevance in disease spread, the ceratopogonid genus Culicoides is still a largely neglected group of species, predominantly because the major human-affecting arboviruses are considered to be transmitted by mosquitoes. However, when a pathogen is detected in a certain vector species, a thorough search for further vectors often remains undone and, therefore, the relevant vector species may remain unknown. Furthermore, for many hematophagous arthropods, true vector competence is often merely suspected and not experimentally proven. Therefore, we aim to illuminate the general impact of Culicoides biting midges and to summarize the knowledge about biting midge-borne disease agents using the order Bunyavirales, the largest and most diverse group of RNA viruses, as an example. When considering only viruses evidentially transmitted by Culicoides midges, the Simbu serogroup (genus Orthobunyavirus) is presumably the most important group within the virus order. Its members are of great veterinary importance, as a variety of simbuviruses, e.g., the species Akabane orthobunyavirus or Schmallenberg orthobunyavirus, induces severe congenital infections in pregnant animals. The major zoonotic representative of this serogroup occurs in South and Central America and causes the so-called Oropouche fever, an acute febrile illness in humans.

Evolutionary and ecological insights into the emergence of arthropod-borne viruses

The emergence of arthropod-borne viruses (arboviruses) is of global concern as they can rapidly spread across countries and to new continents as the recent examples of chikungunya virus and Zika virus have demonstrated. Whereas the global movement patterns of emerging arboviruses are comparatively well studied, there is little knowledge on initial emergence processes that enable sylvatic (enzootic) viruses to leave their natural amplification cycle and infect humans or livestock, often also involving infection of anthropophilic vector species. Emerging arboviruses almost exclusively originate in highly biodiverse ecosystems of tropical countries. Changes in host population diversity and density can affect pathogen transmission patterns and are likely to influence arbovirus emergence processes. This review focuses on concepts from disease ecology, explaining the interplay between biodiversity and pathogen emergence.

Fetal infection with Schmallenberg virus - An experimental pathogenesis study in pregnant cows

Since its first appearance in 2011, Schmallenberg virus (SBV) has been repeatedly detected in aborted ruminant foetuses or severely malformed newborns whose mothers were naturally infected during pregnancy. However, especially the knowledge about dynamics of foetal infection in cattle is still scarce. Therefore, a total of 36 pregnant heifers were experimentally infected during two animal trials with SBV between days 60 and 150 of gestation. The foetuses were collected between 10 and 35 days after infection and virologically and pathologically investigated. Overall, 33 heifers yielded normally developed, macroscopically inconspicuous foetuses, but abundant virus replication was evident at the maternal/foetal interface and viral genome was detectable in at least one organ system of 18 out of 35 foetuses. One heifer was found to be not pregnant at autopsy. One of the animals aborted at day 4 after infection, viral RNA was detectable in the lymphatic tissue of the dam, in the maternal and foetal placenta, and in organs and lymphatic tissue of the foetus. In another foetus, SBV typical malformations like torticollis and arthrogryposis were observed. The corresponding dam was infected at day 90 of pregnancy and viral genome was detectable in the cerebellum of the unborn. Interestingly, no common patterns of infected foetal organs or maternal/foetal placentas could be identified, and both, sites of virus replication and genome loads, varied to a high degree in the individual foetuses. It is therefore concluded, that SBV infects in many cases also the bovine foetus of naïve pregnant cattle, however, the experimentally observed low abortion/malformation rate is in concordance to the reported low rates in the field during the first outbreak wave following the introduction of SBV. This observation speaks for a natural resistance of most bovine foetuses even during the vulnerable phase of early pregnancy, which has to be further studied in the future.

Virological and Serological Responses of Sheep and Cattle to Experimental Schmallenberg Virus Infection

Schmallenberg virus (SBV) is an orthobunyavirus in the Simbu serogroup that emerged in Germany in late 2011 and was mostly associated with a mild transient disease of sheep and cattle. SBV is transmitted by biting midges (Culicoides species) and causes abortions, stillbirths, and congenital defects in naïve pregnant ruminants. Two separate studies were conducted with a primary objective of better understanding the virological and serological responses of sheep and cattle to different SBV isolates after experimental infection. The second objective was to produce immunoreagents and challenge materials for use in future vaccine and diagnostics research. These studies were carried out using the following infectious inocula: (i) infectious serum (IS) (ii) cell culture-grown virus, and (iii) infectious lamb brain homogenate. The responses were assessed in both species throughout the course of the experiment. SBV RNA in serum (RNAemia) was detected as early as 2 (in sheep) and 3 (in cattle) days postinfection (dpi) and peaked on 3 and 4 dpi in cattle and sheep, respectively. Cattle had higher levels of RNAemia compared with sheep. Experimental infection with IS resulted in the highest level of RNAemia in both species followed by cell culture-grown virus. A delayed, low level RNAemia was detected in cattle inoculated with infectious sheep brain. Isolation of SBV was only possible from 4 dpi sera from all cattle inoculated with IS and one sheep inoculated with cell culture-derived virus. SBV neutralizing antibodies were first detected on 14 dpi in both species. No specific gross and microscopic lesions were observed in either study. In conclusion, these studies highlight not only the difference in viremia and anti-SBV antibody level against the different SBV isolates, but also the extent of the response in the two host species.

N-terminal domain of Schmallenberg virus envelope protein Gc delivered by recombinant equine herpesvirus type 1 and modified vaccinia virus Ankara: Immunogenicity and protective efficacy in cattle

Schmallenberg virus (SBV), which emerged in 2011 in Central Europe and subsequently spread very rapidly throughout the continent, affects predominantly ruminants. SBV is transmitted by insect vectors, and therefore vaccination is one of the major tools of disease control. Only recently, a domain connected to virus neutralization has been identified at the amino-terminal part of the viral envelope protein Gc. Here, this Gc domain delivered by recombinant EHV-1 or MVA vector viruses was tested in a vaccination-challenge trial in cattle, one of the major target species of SBV. The EHV-1-based vaccine conferred protection in two of four animals, whereas immunization using the MVA vector vaccine efficiently induced an SBV-specific antibody response and full protection against SBV challenge infection in all the vaccinated animals. Moreover, due to the absence of antibodies against SBVs N-protein, both vector vaccines enable the differentiation between vaccinated and field-infected animals making them to a promising tool to control SBV spread as well as to prevent disease in domestic ruminants.

Schmallenberg Virus: A Novel Virus of Veterinary Importance

In late 2011, unspecific clinical symptoms such as fever, diarrhea, and decreased milk production were observed in dairy cattle in the Dutch/German border region. After exclusion of classical endemic and emerging viruses by targeted diagnostic systems, blood samples from acutely diseased cows were subjected to metagenomics analysis. An insect-transmitted orthobunyavirus of the Simbu serogroup was identified as the causative agent and named Schmallenberg virus (SBV). It was one of the first detections of the introduction of a novel virus of veterinary importance to Europe using the new technology of next-generation sequencing. The virus was subsequently isolated from identical samples as used for metagenomics analysis in insect and mammalian cell lines and disease symptoms were reproduced in calves experimentally infected with both, this culture-grown virus and blood samples of diseased cattle. Since its emergence, SBV spread very rapidly throughout the European ruminant population causing mild unspecific disease in adult animals, but also premature birth or stillbirth and severe fetal malformation when naive dams were infected during a critical phase of gestation. In the following years, SBV recirculated regularly to a larger extend; in the 2014 and 2016 vector seasons the virus was again repeatedly detected in the blood of adult ruminants, and in the following winter and spring months, a number of malformed calves and lambs was born. The genome of viruses present in viremic adult animals showed a very high sequence stability; in sequences generated between 2012 and 2016, only a few amino acid substitutions in comparison to the initial SBV isolate could be detected. In contrast, a high sequence variability was identified in the aminoterminal part of the glycoprotein Gc-encoding region of viruses present in the brain of malformed newborns. This mutation hotspot is independent of the region or host species from which the samples originated and is potentially involved in immune evasion mechanisms.

Role of Schmallenberg virus infection in congenital malformations in ruminants in Scotland in spring 2017

Scotland's Rural College (SRUC), together with the Moredun Research Institute, carries out surveillance for Schmallenberg virus (SBV) infection in cattle and sheep. This article reports findings relating to diagnoses of fetopathy associated with SBV infection and other congenital malformations in these species made between January 1 and May 5, 2017.

Akabane, Aino and Schmallenberg virus-where do we stand and what do we know about the role of domestic ruminant hosts and Culicoides vectors in virus transmission and overwintering?

Akabane, Aino and Schmallenberg virus belong to the Simbu serogroup of Orthobunyaviruses and depend on Culicoides vectors for their spread between ruminant hosts. Infections of adults are mostly asymptomatic or associated with only mild symptoms, while transplacental crossing of these viruses to the developing fetus can have important teratogenic effects. Research mainly focused on congenital malformations has established a correlation between the developmental stage at which a fetus is infected and the outcome of an Akabane virus infection. Available data suggest that a similar correlation also applies to Schmallenberg virus infections but is not yet entirely conclusive. Experimental and field data furthermore suggest that Akabane virus is more efficient in inducing congenital malformations than Aino and Schmallenberg virus, certainly in cattle. The mechanism by which these Simbu viruses cross-pass yearly periods of very low vector abundance in temperate climate zones remains undefined. Yearly wind-borne reintroductions of infected midges from tropical endemic regions with year-round vector activity have been proposed, just as overwintering in long-lived adult midges. Experimental and field data however indicate that a role of vertical virus transmission in the ruminant host currently cannot be excluded as an overwintering mechanism. More studies on Culicoides biology and specific groups of transplacentally infected newborn ruminants without gross malformations are needed to shed light on this matter.

Fetopathic effects of experimental Schmallenberg virus infection in pregnant goats

Schmallenberg virus (SBV) is an emerging virus responsible for congenital malformations in the offspring of domestic ruminants. It is speculated that infection of pregnant dams may also lead to a significant number of unrecognized fetal losses during the early period of gestation. To assess the pathogenic effects of SBV infection of goats in early pregnancy, we inoculated dams at day 28 or 42 of gestation and followed the animals until day 55 of gestation. Viremia in the absence of clinical signs was detected in all virus-inoculated goats. Fetal deaths were observed in several goats infected at day 28 or 42 of gestation and were invariably associated with the presence of viral genomic RNA in the affected fetuses. Among the viable fetuses, two displayed lesions in the central nervous system (porencephaly) in the presence of viral genome and antigen. All fetuses from goats infected at day 42 and the majority of fetuses from goats infected at day 28 of gestation contained viral genomic RNA. Viral genome was widely distributed in these fetuses and their respective placentas, and infectious virus could be isolated from several organs and placentomes of the viable fetuses. Our results show that fetuses of pregnant goats are susceptible to vertical SBV infection during early pregnancy spanning at least the period between day 28 and 42 of gestation. The outcomes of experimental SBV infection assessed at day 55 of gestation include fetal mortalities, viable fetuses displaying lesions of the central nervous system, as well as viable fetuses without any detectable lesion.

Heparan Sulfate Proteoglycan Is an Important Attachment Factor for Cell Entry of Akabane and Schmallenberg Viruses

Akabane virus (AKAV) and Schmallenberg virus (SBV) are members of the genus Orthobunyavirus, which are transmitted by arthropod vectors with a broad cellular tropism in vitro as well as in vivo Both AKAV and SBV cause arthrogryposis-hydranencephaly syndrome in ruminants. The main cellular receptor and attachment factor for entry of these orthobunyaviruses are unknown. Here, we found that AKAV and SBV infections were inhibited by the addition of heparin or enzymatic removal of cell surface heparan sulfates. To confirm this finding, we prepared heparan sulfate proteoglycan (HSPG)-knockout (KO) cells by using a clustered regularly interspaced short palindromic repeat (CRISPR)-Cas9 system and measured the quantities of binding of these viruses to cell surfaces. We observed a substantial reduction in AKAV and SBV binding to cells, limiting the infections by these viruses. These data demonstrate that HSPGs are important cellular attachment factors for AKAV and SBV, at least in vitro, to promote virus replication in susceptible cells.IMPORTANCE AKAV and SBV are the etiological agents of arthrogryposis-hydranencephaly syndrome in ruminants, which causes considerable economic losses in the livestock industry. Here, we identified heparan sulfate proteoglycan as a major cellular attachment factor for the entry of AKAV and SBV. Moreover, we found that heparin is a strong inhibitor of AKAV and SBV infections. Revealing the molecular mechanisms of virus-host interactions is critical in order to understand virus biology and develop novel live attenuated vaccines.

A survey of free-ranging deer in Ireland for serological evidence of exposure to bovine viral diarrhoea virus, bovine herpes virus-1, bluetongue virus and Schmallenberg virus

Background

Deer are an important wildlife species in both the Republic of Ireland and Northern Ireland having colonised most regions across the island of Ireland. In comparison to cattle and sheep which represent the main farmed ruminant species on the island, there is a lack of data concerning their exposure, as measured by the presence of antibodies, to important viral pathogens of ruminants. A study was therefore undertaken to investigate the seroprevalence of wild deer to four viruses, namely bovine viral diarrhoea virus (BVDV), bovine herpesvirus-1 (BoHV-1), Schmallenberg virus (SBV) and bluetongue virus (BTV).

Results

Two panels of sera were assembled; Panel 1 comprised 259 samples (202 collected in the Republic of Ireland and 57 in Northern Ireland) between 2013 and 2015, while Panel 2 comprised 131 samples collected in the Republic of Ireland between 2014 and 2015. Overall sika deer (Cervus nippon) were sampled most commonly (54.8%), followed by fallow deer (Dama dama) (35.3%), with red deer (Cervus elaphus) (4.3%) and hybrid species (0.3%) sampled less frequently, with the species not being recorded for the remaining 5.3% of deer sampled. Age was not recorded for 96 of the 390 deer sampled. 196 of the remainder were adults, while 68 and 30 were yearlings and calves, respectively. Using commercially available enzyme-linked immunosorbent assays, true prevalence and 95% confidence intervals were calculated as 9.9%, (6.8-13.0% CI), SBV; 1.5% (0.1-3.0% CI), BoHV-1; 0.0%, 0-1.7% CI), BVDV; and 0.0%, (0.01-0.10% CI), BTV.

Conclusions

The results indicate a very low seroprevalence for both BVDV and BoHV-1 in the wild deer tested within the study and, are consistent with a very low prevalence in Ireland. While serological cross-reaction with cervid herpesviruses cannot be excluded, the results in both cases suggest that the presence of these viruses in deer is not a significant risk to their control and eradication from the cattle population. This is important given the ongoing programme to eradicate BVDV in Ireland and deliberations on a national eradication programme for BoHV-1. The SBV results show consistency with those reported from cattle and sheep on the island of Ireland, while the BTV results are consistent with this virus remaining exotic to Ireland. The results provide a baseline against which future surveys of either wild or farmed/captive deer populations can be compared.

DNA vaccination regimes against Schmallenberg virus infection in IFNAR-/- mice suggest two targets for immunization

Schmallenberg virus (SBV) is an RNA virus of the Bunyaviridae family, genus Orthobunyavirus that infects wild and livestock species of ruminants. While inactivated and attenuated vaccines have been shown to prevent SBV infection, little is known about their mode of immunity; specifically, which components of the virus are responsible for inducing immunological responses in the host. As previous DNA vaccination experiments on other bunyaviruses have found that glycoproteins, as well as modified (i.e. ubiquitinated) nucleoproteins (N) can confer immunity against virulent viral challenge, constructs encoding for fragments of SBV glycoproteins G_N and G_C, as well as ubiquitinated and non-ubiquitinated N were cloned in mammalian expression vectors, and vaccinated intramuscularly in IFNAR^-/- mice. Upon viral challenge with virulent SBV, disease progression was monitored. Both the ubiquitinated and non-ubiquitinated nucleoprotein candidates elicited high titers of antibodies against SBV, but only the non-ubiquitinated candidate induced statistically significant protection of the vaccinated mice from viral challenge. Another construct encoding for a putative ectodomain of glycoprotein G_C (segment aa. 678-947) also reduced the SBV-viremia in mice after SBV challenge. When compared to other experimental groups, both the nucleoprotein and G_C-ectodomain vaccinated groups displayed significantly reduced viremia, as well as exhibiting no clinical signs of SBV infection. These results show that both the nucleoprotein and the putative G_C-ectodomain can serve as protective immunological targets against SBV infection, highlighting that viral glycoproteins, as well as nucleoproteins are potent targets in vaccination strategies against bunyaviruses.

The N-terminal domain of Schmallenberg virus envelope protein Gc is highly immunogenic and can provide protection from infection

Schmallenberg virus (SBV) is transmitted by insect vectors, and therefore vaccination is one of the most important tools of disease control. In our study, novel subunit vaccines on the basis of an amino-terminal domain of SBV Gc of 234 amino acids (“Gc Amino”) first were tested and selected using a lethal small animal challenge model and then the best performing formulations also were tested in cattle. We could show that neither E. coli expressed nor the reduced form of “Gc Amino” protected from SBV infection. In contrast, both, immunization with “Gc Amino”-encoding DNA plasmids and “Gc-amino” expressed in a mammalian system, conferred protection in up to 66% of the animals. Interestingly, the best performance was achieved with a multivalent antigen containing the covalently linked Gc domains of both, SBV and the related Akabane virus. All vaccinated cattle and mice were fully protected against SBV challenge infection. Furthermore, in the absence of antibodies against the viral N-protein, differentiation between vaccinated and field-infected animals allows an SBV marker vaccination concept. Moreover, the presented vaccine design also could be tested for other members of the Simbu serogroup and might allow the inclusion of additional immunogenic domains.

Effective interference between Simbu serogroup orthobunyaviruses in mammalian cells

The Simbu serogroup of orthobunyaviruses comprises a wide range of viruses with different medical and veterinary relevance. These viruses are known to reassort, and coinfection of the same cell is one of the prerequisites for reassortment. Here, a mammalian cell line was infected with various members of this virus group, inoculated after several time points with a second Simbu serogroup virus, and analyzed by strain or species specific immunofluorescence staining. Different virus species or different strains of the same virus species were able to co-infect mammalian cells, but only for a limited time frame. After a few hours, the replication of the first virus led to a gradual inhibition of a second virus until a complete resistance to superinfection after 24h regardless whether it is another strain of the same virus species or a distinct member of the serogroup.

Eco-social processes influencing infectious disease emergence and spread

The complexity and connectedness of eco-social processes have major influence on the emergence and spread of infectious diseases amongst humans and animals. The disciplinary nature of most research activity has made it difficult to improve our understanding of interactions and feedback loops within the relevant systems. Influenced by the One Health approach, increasing efforts have recently been made to address this knowledge gap. Disease emergence and spread is strongly influenced by host density and contact structures, pathogen characteristics and pathogen population and molecular evolutionary dynamics in different host species, and host response to infection. All these mechanisms are strongly influenced by eco-social processes, such as globalization and urbanization, which lead to changes in global ecosystem dynamics, including patterns of mobility, human population density and contact structures, and food production and consumption. An improved understanding of epidemiological and eco-social processes, including their interdependence, will be essential to be able to manage diseases in these circumstances. The interfaces between wild animals, domestic animals and humans need to be examined to identify the main risk pathways and put in place appropriate mitigation. Some recent examples of emerging infectious disease are described to illustrate eco-social processes that are influencing disease emergence and spread.

Evolutionary origin of pathogenic arthropod-borne viruses-a case study in the family Bunyaviridae

Arthropod-borne viruses have a dual-host tropism and their transmission requires the infection of two disparate hosts, arthropods and vertebrates. Arboviruses occur in several RNA families that also contain viruses with a monotropism for either arthropods or vertebrates. The evolutionary origin of the dual-host tropism of arboviruses was recently identified for the family Bunyaviridae. Bunyaviruses were suggested to have evolved from viruses that are restricted to arthropods as hosts (arthropod-specific viruses). Additional findings of an immense genetic diversity of bunyaviruses in non-blood feeding arthropods support the hypothesis of an arthropod origin of vertebrate-pathogenic bunyaviruses.

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.

Schmallenberg Virus Recurrence, Germany, 2014

Schmallenberg virus (SBV) emerged in Germany in 2011, spread rapidly across Europe, and almost disappeared in 2013. However, since late summer 2014, new cases have occurred in adult cattle. Full-genome analysis revealed some amino acid substitution differences from the first SBV sample. Viremia developed in experimentally infected sheep and cattle for 4-6 days.

Seroprevalence of Schmallenberg virus infection in sheep and goats flocks in Germany, 2012-2013

Schmallenberg virus (SBV) is a member of the family Bunyaviridae and mainly affects ruminants. It is transmitted by biting midges, first and foremost Culicoides spp., and causes congenital malformations reflected in arthrogryposis-hydranencephaly (AH) syndrome. The aim of this study was to collect data on the emergence of SBV as a new arthropod-borne disease introduced into Europe in 2011. Germany was located in the core region of the 2011/2012 epidemic. Following two seroprevalence studies in the north-west of Germany in 2012, this study focused on the epidemiology and distribution of SBV throughout 130 small ruminant flocks in the whole country. Blood samples were obtained of 30 animals per flock and a SBV-specific questionnaire was used to collect operating data of the farms. The median within-herd seroprevalence for all 130 flocks tested was 53.3% with a total range from 0% to 100%. The median within-herd seroprevalence for goats was 30% [interquartile range (IQR): 40.3%] and 57% for sheep (IQR: 43.3%). Small ruminant flocks kept permanently indoors or housed overnight had a significantly lower seroprevalence than flocks kept permanently outdoors. In addition, this study revealed a significantly lower seroprevalence in the north-east of Germany. These results show that small ruminants in Germany are still at risk of contracting new SBV infections following incomplete seroconversion of flocks especially in the north-east of Germany. This might contribute to SBV becoming enzootic in central and northern Europe. Furthermore, the survey revealed that housing animals at least during mating and early pregnancy may reduce the risk of new SBV infections and may thus be an option to reduce losses as long as there is no licensed vaccine available on the German market.

Circulation of a Simbu Serogroup Virus, Causing Schmallenberg Virus-Like Clinical Signs in Northern Jordan

Schmallenberg virus (SBV)-like clinical cases of abortions in northern Jordan in early 2013, together with the emergence of SBV in Europe in 2011, its rapid spread within the following years and the detection of this virus in Turkey, raised questions about the distribution of SBV or related orthobunyaviruses. To evaluate the occurrence of SBV or related members of the Simbu serogroup of orthobunyaviruses in Jordan, bulk milk (cattle) and serum samples (cattle, sheep and goat) collected in northern Jordan in 2013 were first tested by commercially available SBV antibody ELISAs. Indeed, 3 of 47 bulk milk samples and 57 of 115 serum samples provided positive results, but SBV specificity of the ELISA results could not be confirmed by virus neutralization assays. Instead, subsequent cross-neutralization tests were able to further investigate the specificity of these antibodies. Here, a significant inhibition of Aino virus was observed. Thus, the causative agent was most likely a Simbu serogroup virus closely related to Aino virus. Consequently, these results confirm that members of this group of virus are not only present in Europe, Africa or Australia, but also in the Middle East.

Analysis of the humoral immune response against the envelope glycoprotein Gc of Schmallenberg virus reveals a domain located at the amino terminus targeted by mAbs with neutralizing activity

Orthobunyaviruses are enveloped viruses that are arthropod-transmitted and cause disease in humans and livestock. Viral attachment and entry are mediated by the envelope glycoproteins Gn and Gc, and the major glycoprotein, Gc, of certain orthobunyaviruses is targeted by neutralizing antibodies. The domains in which the epitopes of such antibodies are located on the glycoproteins of the animal orthobunyavirus Schmallenberg virus (SBV) have not been identified. Here, we analysed the reactivity of a set of mAbs and antisera against recombinant SBV glycoproteins. The M-segment-encoded proteins Gn and Gc of SBV were expressed as full-length proteins, and Gc was also produced as two truncated forms, which consisted of its amino-terminal third and carboxyl-terminal two-thirds. The sera from convalescent animals reacted only against the full-length Gc and its subdomains and not against the SBV glycoprotein Gn. Interestingly, the amino-terminal domain of SBV-Gc was targeted not only by polyclonal sera but also by the majority of murine mAbs with a neutralizing activity. Furthermore, the newly defined amino-terminal domain of about 230 aa of the SBV Gc protein could be affinity-purified and further characterized. This major neutralizing domain might be relevant for the development of prophylactic, diagnostic and therapeutic approaches for SBV and other orthobunyaviruses.

Culicoides vector species on three South American camelid farms seropositive for bluetongue virus serotype 8 in Germany 2008/2009

Palearctic species of Culicoides (Diptera, Ceratopogonidae), in particular of the Obsoletus and Pulicaris complexes, were identified as putative vectors of bluetongue virus serotype 8 (BTV-8) on ruminant farms during the epizootic in Germany from 2006 to 2009. BTV may cause severe morbidity and mortality in ruminants and sporadically in South American camelids (SAC). However, the fauna of Culicoides spp. on SAC farms has not been investigated. Therefore, the ceratopogonid fauna was monitored on three farms with BTV-seropositive SAC in Germany. Black-light traps were set up on pastures and in stables from summer 2008 to autumn 2009. Additionally, ceratopogonids were caught in emergence traps mounted on llama dung and dung-free pasture from spring to autumn 2009. After morphological identification, selected Culicoides samples were analysed for BTV-RNA by real-time RT-PCR. The effects of the variables 'location', 'temperature' and 'humidity' on the number of Culicoides caught in black-light traps were modelled using multivariable Poisson regression. In total, 26 species of Culicoides and six other genera of biting midges were identified. The most abundant Culicoides spp. collected both outdoors and indoors with black-light traps belonged to the Obsoletus (77.4%) and Pulicaris (16.0%) complexes. The number of Culicoides peaked in summer, while no biting midges were caught during the winter months. Daily collections of Culicoides were mainly influenced by the location and depended on the interaction of temperature and humidity. In the emergence traps, species of the Obsoletus complex predominated the collections. In summary, the absence of BTV-RNA in any of the analysed Culicoides midges and in the BTV-seropositive SAC on the three farms together with the differences in the pathogenesis of BTV-8 in SAC compared to ruminants suggests a negligible role of SAC in the spread of the virus. Although SAC farms may provide similar suitable habitats for putative Culicoides vectors than ruminant farms, the results suggest that geographic and meteorological factors had a stronger influence on Culicoides abundance than the animal species.

Schmallenberg virus antibody development and decline in a naturally infected dairy cattle herd in Germany, 2011-2014

In late 2011, the novel insect-transmitted orthobunyavirus Schmallenberg virus (SBV) emerged in Central Europe. Since that year, a dairy cattle herd kept in the German region in which the virus was initially detected was continuously monitored. In order to evaluate the development of the within-herd seroprevalence, but also to assess the long-term persistence of antibodies against SBV in individual animals, blood samples of all cows older than 24 months were taken yearly after the respective vector season and serologically analyzed. In December 2011, in 74% of the tested animals SBV-specific antibodies were detectable. Additional scattered seroconversions were observed between the 2011 and 2012 vector seasons, thereafter all seronegative animals remained negative. Until December 2014, the intra-herd seroprevalence decreased to 58%. A total of 122 cows infected presumable in autumn 2011 were sampled every year, 9 of them became seronegative until December 2014. Consequently, though SBV-specific antibodies were detected in about 90% of the monitored animals for more than three years, a lifelong antibody-based immunity is not expected in every animal. The loss of anti-SBV antibodies in individual animals combined with the missing infection of young stock results in a declining herd seroprevalence and increases the risk of a renewed virus circulation to a greater extent within the next years.