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Arthropod-borne orthobunyaviruses belonging to the Simbu serogroup can cause congenital and neurological disease in livestock. Across Australia, the National Arbovirus Monitoring Program (NAMP) conducts surveillance for veterinary-important arboviruses. Our study complements this broader surveillance framework by investigating the virus-specific transmission patterns of Simbu group viruses (SGVs) present in New South Wales (NSW). To describe the distribution of six SGVs: Akabane, Aino, Douglas, Peaton, Tinaroo, and a recently recognised Shamonda-like virus, we examined 24 years of serological data (2000-2023) from NSW sentinel cattle. The transmission of a Simbu serogroup virus was detected during every monitoring period (October-July), progressing from north to south along the NSW coastline. Inland transmission west of the Great Dividing Range (GDR) was intermittent (2012-2013, 2020, and 2022), when SGV distribution extended across the mountain range or progressed down the western slopes from Queensland. From 2014, repeated seasonal SGV transmission extended to the far south coast of NSW. Peaton virus was the most frequently detected and widely distributed virus. Since testing for the newly detected Shamonda-like virus started in 2019, this virus has been widely detected across coastal NSW and often in herds also infected with Douglas or Peaton viruses. Discrepancies between the ELISA and virus neutralisation test (VNT) results suggest that this virus could have been present in NSW as early as 2012. From 2017, Akabane virus has a sporadic distribution. The distribution for both Aino and Tinaroo viruses was sporadic (2005-2023). These findings highlight the importance of long-term, virus-specific surveillance in identifying emerging variants and detecting exotic incursions.

Important lessons have been learned by the Israeli veterinary community regarding Simbu serogroup viruses infections. This serogroup of viruses might cause the births of neonatal malformation in susceptible ruminant’s populations. Until 2012, only Akabane virus was connected with the births of malformed ruminants in Israel. However, serological and genomic detection tests, coupled with viral isolations, revealed that more than a single Simbu serogroup serotype could be present concurrently in the same farm or even in the same animal. From 2012 to date, Aino, Shuni, Shamunda, Satuperi, Peaton, Schmallenberg, and Sango viruses have been found in Israel either by serological or genomic investigation. Israel is located in the Eastern Mediterranean Basin, a terrestrial and climatic bridge between the three old continents. The Eastern Mediterranean shores benefit from both the tropical/subtropical and the continental climatic conditions. Therefore, the Eastern Mediterranean basin might serve as an optimal investigatory compound for several arboviral diseases, acting as a sentinel. This review summarizes updated information related to the presence of Simbu serogroup viruses in Israel.

Two viruses isolated from Culicoides biting midges in Japan and preserved in a frozen state for over three decades were genetically characterized by next-generation sequencing. The viruses have a tripartite RNA genome with the typical coding strategy of orthobunyaviruses. They also share a high level of genetic similarity and are thus regarded as isolates of the same virus. Pairwise sequence comparisons and phylogenetic analysis including viruses of the Simbu serogroup demonstrated that the new viruses are members of clade A of this serogroup. In addition, a discrepancy in the phylogenetic trees indicated that a genetic reassortment had occurred in the evolution of the studied viruses. The L protein of the virus reported here showed no more than 94.6% amino acid sequence identity to that of any other Simbu serogroup virus, indicating that it should be regarded as a novel virus according to a criterion for species definition in the genus Orthobunyavirus. Therefore, this novel virus is tentatively named ‘Taniyama virus’ based on the location where the infected midges were collected.

Viruses of the Simbu serogroup are arboviruses that are known to cause outbreaks of abortion, stillbirth and congenitally deformed neonates. This study presents the results of antibody screening of Simbu serogroup viruses in heifers born in Israel after October 2013, and in adult milking cows born before May 2012. Thirteen dairy cattle farms in five regions, and one sheep flock, entered this study. Serum samples that were found to be positive by ELISA were further tested by specific virus- neutralization test against a panel of Simbu serogroup viruses including Akabane, Aino, Sathuperi, Shamonda, and Peaton viruses. Antibody detection in lactating adult cows revealed that several viruses were circulating in Israel between 2008-2014. Moreover, during autumn 2014 the heifers became serum-positive after being exposed to more than one Simbu serogroup virus concurrently. The results of this study shed new light on Simbu virus infections in Israel, and may contribute to the epidemiology of the Simbu serogroup around the Mediterranean Basin in general.

Oropouche virus (OROV) is the unique known human pathogen belonging to serogroup Simbu of Orthobunyavirus genus and Bunyaviridae family. OROV is transmitted by wild mosquitoes species to sloths, rodents, monkeys and birds in sylvatic environment, and by midges ( Culicoides paraensis and Culex quinquefasciatus ) to man causing explosive outbreaks in urban locations. OROV infection causes dengue fever-like symptoms and in few cases, can cause clinical symptoms of aseptic meningitis. OROV contains a tripartite negative RNA genome encapsidated by the viral nucleocapsid protein (NP), which is essential for viral genome encapsidation, transcription and replication. Here, we reported the first study on the structural properties of a recombinant NP from human pathogen Oropouche virus (OROV–rNP). OROV–rNP was successfully expressed in E. coli in soluble form and purified using affinity and size-exclusion chromatographies. Purified OROV–rNP was analyzed using a series of biophysical tools and molecular modeling. The results showed that OROV–rNP formed stable oligomers in solution coupled with endogenous E. coli nucleic acids (RNA) of different sizes. Finally, electron microscopy revealed a total of eleven OROV–rNP oligomer classes with tetramers (42%) and pentamers (43%) the two main populations and minor amounts of other bigger oligomeric states, such as hexamers, heptamers or octamers. The different RNA sizes and nucleotide composition may explain the diversity of oligomer classes observed. Besides, structural differences among bunyaviruses NP can be used to help in the development of tools for specific diagnosis and epidemiological studies of this group of viruses.

Simbu serogroup are arbo‐ viruses which are mainly transmitted by Culicoides. Two members of the Simbu serogroup, Akabane and Shuni viruses, have been isolated from congenitally malformed ruminants in Israel. A recent serosurvey revealed that Israeli ruminants have been exposed to several additional Simbu viruses, including Shamonda and Sathuperi that seems to be circulating in Israel. In April 2017, an apparently healthy one‐month‐old male calf was transferred to the Kimron Veterinary Institute. A few days later, the calf was reported to be slow to respond to its surroundings and was not able to feed on its own. Blindness was observed upon clinical examination. RNA of the small, medium and large segments of Simbu serogroup viruses were amplified and sequenced from the testis tissues and from the Cerebrospinal fluid (CSF). During post‐mortem examination, hydranencephaly was defined. Phylogenetic analysis of all three segments of Simbu serogroup viruses showed that the sequences detected in the Israeli calf were virtually identical to Peaton virus (PEAV). PEAV was also detected in two pools of Culicoides imicola trapped at two different locations in Israel. This is the first genomic detection of PEAV outside Australia and Japan. These results are of epidemiological significance, as they demonstrate that PEAV is circulating in Israel and affects cattle. Consequently, these results are also of relevance to a potential spread of Simbu serogroup viruses into Europe. Genomic fragments of Peaton virus were detected in a calf exhibiting micro‐hydranenchepaly and in two pools of Culicides imicola in Israel. This is the first genomic detection of this virus outside Australia and Japan. Our results are of relevance to the potential spread of Simbu viruses into Europe.

BACKGROUND: Schmallenberg virus (SBV), a novel orthobunyavirus of the Simbu serogroup, was first identified in October 2011 in dairy cattle in Germany, where it caused fever, diarrhea and a drop in milk yield. Since then, SBV additionally has been detected in adult sheep and goats. Although symptoms of acute infection were not observed, infection during a vulnerable phase of pregnancy caused congenital malformations and stillbirths. In view of the current situation and the possible emergence of further Simbu serogroup members, a pan-Simbu real-time reverse transcriptase (RT) PCR system for the reliable detection of Simbu serogroup viruses should be developed. METHODS: In this study a pan-Simbu real-time RT-PCR system was established and compared to several SBV real-time RT-PCR assays. All PCR-systems were tested using a panel of different Simbu serogroup viruses as well as several field samples from diseased cattle, sheep and goats originating from all over Germany. Several pan-Simbu real-time RT-PCR products were sequenced via Sanger sequencing. Furthermore, in silico analyses were performed to investigate suitability for the detection of further orthobunyaviruses. RESULTS: All tested members of the Simbu serogroup (n = 14) as well as most of the field samples were successfully detected by the pan-Simbu real-time RT-PCR system. The comparison of this intercalating dye assay with different TaqMan probe-based assays developed for SBV diagnostics confirmed the functionality of the pan-Simbu assay for screening purposes. However, the SBV-TaqMan-assay SBV-S3 delivered the highest analytical sensitivity of less than ten copies per reaction for duplex systems including an internal control. In addition, for confirmation of SBV-genome detection the highly specific SBV-M1 assay was established. CONCLUSION: The pan-Simbu real-time RT-PCR system was able to detect all tested members of the Simbu serogroup, most of the SBV field samples as well as three tested Bunyamwera serogroup viruses with a suitable sensitivity. According to in silico analyses, this system seems to be able to detect a broad orthobunyavirus spectrum. As an additional feature of the pan-Simbu real-time RT-PCR system, subsequent species classification via sequencing is feasible. Regarding SBV diagnostics, the performance of the S-segment targeting SBV-S3 assay was superior with respect to the analytical sensitivity.

In 1999, two viruses were isolated from blood samples of sentinel cattle in the Western part of Japan. The physiochemical and morphological properties of these viruses indicated that they belonged to the family Bunyaviridae. Sequence analysis of the S segment indicates that the two viruses are closely related to Sathuperi virus (SATV). The N-terminal 168 amino acid of the G2 protein of the M segment was highly homologous with that of SATV (98.2%). Given these results, we conclude that the newly isolated viruses are closest to SATV, which was initially isolated in India and Nigeria over 30 years ago.

Orthobunyaviruses (order Bunyavirales, family Peribunyaviridae) in the Simbu serogroup have been responsible for widespread epidemics of congenital disease in ruminants. Australia has a national program to monitor arboviruses of veterinary importance. While monitoring for Akabane virus, a novel orthobunyavirus was detected. To inform the priority that should be given to this detection, a scoping review was undertaken to (1) characterise the associated disease presentations and establish which of the Simbu group viruses are of veterinary importance; (2) examine the diagnostic assays that have undergone development and validation for this group of viruses; and (3) describe the methods used to monitor the distribution of these viruses. Two search strategies identified 224 peer-reviewed publications for 33 viruses in the serogroup. Viruses in this group may cause severe animal health impacts, but only those phylogenetically arranged in clade B are associated with animal disease. Six viruses (Akabane, Schmallenberg, Aino, Shuni, Peaton, and Shamonda) were associated with congenital malformations, neurological signs, and reproductive disease. Diagnostic test interpretation is complicated by cross-reactivity, the timing of foetal immunocompetence, and sample type. Serological testing in surveys remains a mainstay of the methods used to monitor the distribution of SGVs. Given significant differences in survey designs, only broad mean seroprevalence estimates could be provided. Further research is required to determine the disease risk posed by novel orthobunyaviruses and how they could challenge current diagnostic and surveillance capabilities.