Bluetongue Research Articles

Climate correlates of bluetongue incidence in southern Portugal.

Model forecasts of the spatiotemporal occurrence dynamics of diseases are necessary and can help understand and thus manage future disease outbreaks. In our study, we used ecological niche modelling to assess the impact of climate on the vector suitability for bluetongue disease, a disease affecting livestock production with important economic consequences. Specifically, we investigated the relationship between the occurrence of bluetongue outbreaks and the environmental suitability of each of the four vector species studied. We found that the main vector for bluetongue disease, Culicoides imicola, a typically tropical and subtropical species, was a strong predictor for disease outbreak occurrence in a region of southern Portugal from 2004 to 2021. The results highlight the importance of understanding the climatic factors that might influence vector presence to help manage infectious disease impacts. When diseases impact economically relevant species, the impacts go beyond mortality and have important economic consequences.

Potential role of peste des petits ruminants virus in small ruminant abortions

The aim of the present study was to investigate the frequency, genetic variability, and phylogeny of the peste des petits ruminants virus (PPRV) in ovine and caprine fetuses. During 2014 and 2017, a total of 1054 embryos/fetuses were collected in Turkey. A real-time RT-PCR assay was used for the detection of the PPRV RNA. Genetic characterization and phylogenetic analysis of the PPRV field isolates were conducted by sequencing fusion (F) protein and nucleoprotein (N) gene segments. Samples were also collected from ewes (n = 83) and nanny goats (n = 3) that had aborted and whose embryos/fetuses were found to be PPRV positive. PPRV positive embryos/fetuses were also tested for the presence of Listeria monocytogenes, Campylobacter spp., Coxiella burnetii, Chlamydophila abortus, Brucella spp., akabane virus, aino virus, bluetongue virus, border disease virus, bovine viral diarrhea virus, Cache Valley virus, and Schmallenberg virus. PPRV RNA was detected in 123 (11.7 %) of the 1054 embryos/fetuses, 78 of the 83 (94 %) ewes and 3 (100 %) nanny goats. Border disease virus RNA and Chlamydophila abortus DNA were detected in 7 and 12 PPRV positive sheep fetuses, respectively, while other bacterial and viral agents were not detected. Phylogenetically, the field isolates in this study belong to lineage IV, and compared to other strains of lineage IV considered in this study, they showed 1 and 5 new amino acid substitutions in the F and N gene sequences, respectively. The results of the study suggest that PPRV plays an important role in abortion. Therefore, PPRV needs to be taken into consideration in sheep and goats abortions.

Understanding the Pathogenesis of Endothelial Injury Induced by Bluetongue Virus in Experimentally Infected Sheep

Bluetongue (BT) is an economically important contagious viral disease transmitted by insect vectors of Culicoides species affecting both domestic and wild ruminants caused by Genus Orbivirus of Reoviridae family. Present in vivo study for the first time conducted to understand the role of oxidative stress and acute phase proteins in the pathogenesis of endothelial injury in target blood vessels of BTV-4 infected sheep. Twelve sheep of either sex were divided into two groups of six animals each and infected intradermally at multiple sites in the neck region with 6×105.9 TCID50/ml of BTV-4 and animals of control group were inoculated with uninfected tissue culture fluid. Animals were sacrificed at 3, 7, 15, 28, 60, and 90 days post infection (dpi) and postmortem examination was conducted. Oxidative stress parameters like LPO, SOD, GPO and catalase in the blood vessels, hemolysate and serum were estimated. Oxidative stress parameter like LPO was upregulated and anti-oxidant parameters like SOD and GPO were downregulated in blood vessels homogenates, hemolysate and serum of BTV-4 infected animals than uninfected control. This shows the role of oxidative stress in causing endothelial cell damage during BTV infection. Acute phase proteins like CRP and fibrinogen in serum and plasma were estimated and found upregulated in BTV-4 infected animals, which shows that inflammatory changes during the disease causes vascular damage. Prothrombin time was estimated in plasma of BTV-4 infected animals and was prolonged in BTV infected animals indicating coagulation disorder. Increased oxidative stress and fibrinogen, and prolonged prothrombin time indicated the coagulation disorders induced by BTV infection by causing endothelial cell damage and severe vascular disease results in congestion, haemorrhages and edema in the blood vessels and other target organs in sheep.

Genetic and antigenic characterization of bluetongue virus serotype-1 isolated from goat in India

Genetic and antigenic characterization of bluetongue virus serotype-1 isolated from goat in India

Reference Material Production and Milk Protein Concentration as Elements to Improve Bluetongue Serological Diagnosis in Bulk Tank Milk.

The serological surveillance of bluetongue in bulk tank milk is an efficient and cost-effective method for the early detection of bluetongue virus incursions in unvaccinated free areas of the disease. In addition, the availability of standardized and reliable reagents and refined diagnostic procedures with high sensitivity and specificity are essential for surveillance purposes. However, no available reference materials for bluetongue virus serological surveillance in bulk tank milk exist. This study shows the production and characterization of reference material for the implementation of a commercially available bluetongue milk ELISA test in official laboratories, as well as the evaluation of a procedure to increase the sensitivity in samples with low levels of antibodies. This procedure, based on milk protein concentration, allowed us to notably increase the ELISA test's analytical sensitivity, which is useful for milk samples from farms with low within-herd prevalence or pools of bulk tank milk samples. The standardized milk reference material produced here, together with the evaluated procedure to improve analytical sensitivity, could be applied as tools to ensure an accurate diagnosis by official laboratories in bluetongue unvaccinated free areas.

Ecological niche modelling of Culicoides imicola and future range shifts under climate change scenarios in Italy.

Culicoides imicola is the main vector of viral diseases of livestock in Europe such as bluetongue (BT), African horse sickness and epizootic haemorrhagic disease. Climatic factors are the main drivers of C. imicola occurrence and its distribution might be subject to rapid shifts due to climate change. Entomological data, collected during BT surveillance, and climatic/environmental variables were used to analyse ecological niche and to model C. imicola distribution and possible future range shifts in Italy. An ensemble technique was used to weigh the performance of machine learning, linear and profile methods. Updated future climate projections from the latest phase of the Climate Model Intercomparison Project were used to generate future distributions for the next three 20-year periods, according to combinations of general circulation models and shared socioeconomic pathways and considering different climate change scenarios. Results indicated the minimum temperature of the coldest month (BIO 6) and precipitation of the driest-warmest months (BIO 14) as the main limiting climatic factors. Indeed, BIO 6 and BIO 14 reported the two highest values of variable importance, respectively, 9.16% (confidence interval [CI] = 7.99%-10.32%), and 2.01% (CI = 1.57%-2.44%). Under the worst-case scenario of climate change, C. imicola range is expected to expand northward and shift away from the coasts of central Italy, while in some areas of southern Italy, environmental suitability will decrease. Our results provide predictions of C. imicola distribution according to the most up-to-date future climate projections and should be of great use to surveillance management at regional and national scales.

Genome sequences of the 15 bluetongue virus vaccine strains incorporated in the South African live-attenuated vaccine.

Bluetongue disease in endemic areas is predominantly controlled through vaccination with live-attenuated vaccines. Sequencing of the original master seed viruses used in the production of Onderstepoort Biological Products vaccine was conducted. Nucleotide identities of 82.97%-100% were obtained for all sequences when compared to South African reference strains.

Recruitment of multi-segment genomic RNAs by Bluetongue virus requires a preformed RNA network.

How do segmented RNA viruses correctly recruit their genome has yet to be clarified. Bluetongue virus is a double-stranded RNA virus with 10 segments of different sizes, but it assembles its genome in single-stranded form through a series of specific RNA-RNA interactions prior to packaging. In this study, we determined the structure of each BTV transcript, individually and in different combinations, using 2'-hydroxyl acylation analysed by primer extension and mutational profiling (SHAPE-MaP). SHAPE-MaP identified RNA structural changes during complex formation and putative RNA-RNA interaction sites. Our data also revealed a core RNA-complex of smaller segments which serves as the foundation ('anchor') for the assembly of a complete network composed of ten ssRNA segments. The same order of core RNA complex formation was identified in cells transfected with viral RNAs. No viral protein was required for these assembly reactions. Further, substitution mutations in the interacting bases within the core assemblies, altered subsequent segment addition and affected virus replication. These data identify a wholly RNA driven reaction that may offer novel opportunities for designed attenuation or antiviral therapeutics.

Global Research on Bluetongue: A Bibliometric Analysis

Bluetongue (BT) is a viral disease characterized by swelling and cyanosis of the tongue, capable of infecting both domestic and wild animal species. Bluetongue virus (BTV) can cause an outbreak in any region of the world where favorable temperature and vector presence conditions exist. For this reason, BTV studies remain an active field in the literature and the research network of this field continues to develop. This paper aims to identify the most influential research elements and collaborations in the BTV field, with a discussion of results based on existing literature. To discover the current literature on BTV, the Web of Science database was employed. The dataset consisted of 1315 articles. The “Bibliometrix” R package and the VOSviewer program were utilized for data analysis. The number of BT studies rose dramatically between 2005 and 2016 with the appearance of BTV in Europe. The USA and England were determined as the most influential countries. The Veterinary Microbiology and Medical and Veterinary Entomology journals were identified as the most prominent journals of the field. It has been determined that serological studies have been a focal point and collaborations have been strengthened in the field of BTV. Conversely, financing sources and collaboration levels regarding BTV studies were found to be inadequate in African and Asian countries. This paper is expected to provide information to researchers interested in BTV studies about the intellectual structure of the field.

Culicoides Midge Abundance across Years: Modeling Inter-Annual Variation for an Avian Feeder and a Candidate Vector of Hemorrhagic Diseases in Farmed Wildlife

(1) Background: Epizootic hemorrhagic disease virus (EHDV) and bluetongue virus (BTV) are orbiviruses that cause hemorrhagic disease (HD) with significant economic and population health impacts on domestic livestock and wildlife. In the United States, white-tailed deer (Odocoileus virginianus) are particularly susceptible to these viruses and are a frequent blood meal host for various species of Culicoides biting midges (Diptera: Ceratopogonidae) that transmit orbiviruses. The species of Culicoides that transmit EHDV and BTV vary between regions, and larval habitats can differ widely between vector species. Understanding how midges are distributed across landscapes can inform HD virus transmission risk on a local scale, allowing for improved animal management plans to avoid suspected high-risk areas or target these areas for insecticide control. (2) Methods: We used occupancy modeling to estimate the abundance of gravid (egg-laden) and parous (most likely to transmit the virus) females of two putative vector species, C. stellifer and C. venustus, and one species, C. haematopotus, that was not considered a putative vector. We developed a universal model to determine habitat preferences, then mapped a predicted weekly midge abundance during the HD transmission seasons in 2015 (July–October) and 2016 (May–October) in Florida. (3) Results: We found differences in habitat preferences and spatial distribution between the parous and gravid states for C. haematopotus and C. stellifer. Gravid midges preferred areas close to water on the border of well and poorly drained soil. They also preferred mixed bottomland hardwood habitats, whereas parous midges appeared less selective of habitat. (4) Conclusions: If C. stellifer is confirmed as an EHDV vector in this region, the distinct spatial and abundance patterns between species and physiological states suggest that the HD risk is non-random across the study area.

Seasonal change and influence of environmental variables on host-seeking activity of the biting midge Culicoides sonorensis at a southern California dairy, USA

BackgroundAs a primary vector of bluetongue virus (BTV) in the US, seasonal abundance and diel flight activity of Culicoides sonorensis has been documented, but few studies have examined how time of host-seeking activity is impacted by environmental factors. This knowledge is essential for interpreting surveillance data and modeling pathogen transmission risk.MethodsThe diel host-seeking activity of C. sonorensis was studied on a California dairy over 3 years using a time-segregated trap baited with CO2. The relationship between environmental variables and diel host-seeking activity (start, peak, and duration of activity) of C. sonorensis was evaluated using multiple linear regression. Fisher’s exact test and paired-sample z-test were used to evaluate the seasonal difference and parity difference on diel host-seeking activity.ResultsHost-seeking by C. sonorensis began and reached an activity peak before sunset at a higher frequency during colder months relative to warmer months. The time that host-seeking activity occurred was associated low and high daily temperature as well as wind speed at sunset. Colder temperatures and a greater diurnal temperature range were associated with an earlier peak in host-seeking. Higher wind speeds at sunset were associated with a delayed peak in host-seeking and a shortened duration of host-seeking. Parous midges reached peak host-seeking activity slightly later than nulliparous midges, possibly because of the need for oviposition by gravid females before returning to host-seeking.ConclusionsThis study demonstrates that during colder months C. sonorensis initiates host-seeking and reaches peak host-seeking activity earlier relative to sunset, often even before sunset, compared to warmer months. Therefore, the commonly used UV light-baited traps are ineffective for midge surveillance before sunset. Based on this study, surveillance methods that do not rely on light trapping would provide a more accurate estimate of host-biting risk across seasons. The association of environmental factors to host-seeking shown in this study can be used to improve modeling or prediction of host-seeking activity. This study identified diurnal temperature range as associated with host-seeking activity, suggesting that Culicoides may respond to a rapidly decreasing temperature by shifting to an earlier host-seeking time, though this association needs further study.Graphical

Treatment considerations for bluetongue virus serotype‐3 cases in sheep

Background: Bluetongue virus (BTV) serotype‐3 (BTV‐3) has been circulating in the Netherlands since September 2023 and was first reported in Kent in the UK in November 2023, picked up via the annual bluetongue surveillance programme. It is a highly pathogenic strain in sheep with limited preventive measures once virus is circulating in the biting midge population. At the time of publication there is no BTV‐3 vaccine available and no cross‐protection from other BTV vaccine strains. There are no specific antiviral medicines available, and therapy focuses on nursing care and anti‐inflammatory medicines to reduce clinical signs, although early euthanasia decisions need to be considered on the grounds of animal welfare.Aim of the article: This article takes the experiences of vets from the Netherlands and describes what practitioners might be able to do to treat clinical cases of BTV‐3, with thanks to Schapendokter (2023) for sharing their practice protocols.

Dealing with cases of bluetongue virus serotype‐3 in sheep

Dealing with cases of bluetongue virus serotype‐3 in sheep

Transcriptomic Investigation of the Virus Spectrum Carried by Midges in Border Areas of Yunnan Province.

Yunnan province in China shares its borders with three neighboring countries: Myanmar, Vietnam, and Laos. The region is characterized by a diverse climate and is known to be a suitable habitat for various arthropods, including midges which are notorious for transmitting diseases which pose significant health burdens affecting both human and animal health. A total of 431,100 midges were collected from 15 different locations in the border region of Yunnan province from 2015 to 2020. These midges were divided into 37 groups according to the collection year and sampling site. These 37 groups of midges were then homogenized to extract nucleic acid. Metatranscriptomics were used to analyze their viromes. Based on the obtained cytochrome C oxidase I gene (COI) sequences, three genera were identified, including one species of Forcipomyia, one species of Dasyhelea, and twenty-five species of Culicoides. We identified a total of 3199 viruses in five orders and 12 families, including 1305 single-stranded positive-stranded RNA viruses (+ssRNA) in two orders and seven families, 175 single-stranded negative-stranded RNA viruses (-ssRNA) in two orders and one family, and 1719 double-stranded RNA viruses in five families. Six arboviruses of economic importance were identified, namely Banna virus (BAV), Japanese encephalitis virus (JEV), Akabane virus (AKV), Bluetongue virus (BTV), Tibetan circovirus (TIBOV), and Epizootic hemorrhagic disease virus (EHDV), all of which are capable, to varying extents, of causing disease in humans and/or animals. The survey sites in this study basically covered the current distribution area of midges in Yunnan province, which helps to predict the geographic expansion of midge species. The complexity and diversity of the viral spectrum carried by midges identified in the study calls for more in-depth research, which can be utilized to monitor arthropod vectors and to predict the emergence and spread of zoonoses and animal epidemics, which is of great significance for the control of vector-borne diseases.

Spatial Transmission Characteristics of the Bluetongue Virus Serotype 3 Epidemic in The Netherlands, 2023.

A devastating bluetongue (BT) epidemic caused by bluetongue virus serotype 3 (BTV-3) has spread throughout most of the Netherlands within two months since the first infection was officially confirmed in the beginning of September 2023. The epidemic comes with unusually strong suffering of infected cattle through severe lameness, often resulting in mortality or euthanisation for welfare reasons. In total, tens of thousands of sheep have died or had to be euthanised. By October 2023, more than 2200 locations with ruminant livestock were officially identified to be infected with BTV-3, and additionally, ruminants from 1300 locations were showing BTV-associated clinical symptoms (but not laboratory-confirmed BT). Here, we report on the spatial spread and dynamics of this BT epidemic. More specifically, we characterized the distance-dependent intensity of the between-holding transmission by estimating the spatial transmission kernel and by comparing it to transmission kernels estimated earlier for BTV-8 transmission in Northwestern Europe in 2006 and 2007. The 2023 BTV-3 kernel parameters are in line with those of the transmission kernel estimated previously for the between-holding spread of BTV-8 in Europe in 2007. The 2023 BTV-3 transmission kernel has a long-distance spatial range (across tens of kilometres), evidencing that in addition to short-distance dispersal of infected midges, other transmission routes such as livestock transports probably played an important role.

Influence of Rearing Temperatures on Oviposition and Survivability of Developmental Stages of Culicoides peregrinus Vector of Bluetongue Virus with a Note on Egg Viability

Influence of Rearing Temperatures on Oviposition and Survivability of Developmental Stages of Culicoides peregrinus Vector of Bluetongue Virus with a Note on Egg Viability

Impacts of Climate Change on Vector-Borne Diseases of Animals and Humans with Special Emphasis on Afghanistan

Vectors are organisms that transmit pathogenic microorganisms among animals and humans. Infections transmitted by the bites of blood-sucking arthropods are called vector-borne diseases (VBDs). This review highlights the impacts of climate change on the distribution, seasonal variation, and socioeconomic effects of VBDs in affected countries, especially Afghanistan. There is good enough evidence indicating that recent climate change has affected the interaction of the vector-pathogen-host cycle in many parts of the world. The emergence and re-emergence of bluetongue virus (BTV), Rift Valley Fever (RVF), lumpy skin disease (LSD), West Nile Virus (WNV), and malaria in new areas previously considered free of the diseases, and shift of seasonal occurrence of many VBDs in endemic areas, are the clear examples of climate change impacts on VDBs. Although significant progress has been made regarding VBD surveillance systems, diagnostic capacity, vaccine development, and vector control programs in resource-rich countries, failure in adaptation programs and ineffective mitigation strategies against VBDs in developing countries, especially in low and middle-income countries (LMICs), including Afghanistan facilitate widespread distribution of VBDs in these regions. Furthermore, developing drug resistance among the pathogens and their vectors makes the conditions more suitable for VBDs wide dispersion. Such situations cause severe health and socio-economic burdens to affected countries. Developing early-warning systems for detecting VBDs, identifying and developing resistant livestock species and breeds, and applying interceptive measures based on integrated research programs are crucial to effectively reduce the harmful impacts of VBDs on human and animal populations.

RNA genome packaging and capsid assembly of bluetongue virus visualized in host cells

Unlike those of double-stranded DNA (dsDNA), single-stranded DNA (ssDNA), and ssRNA viruses, the mechanism of genome packaging of dsRNA viruses is poorly understood. Here, we combined the techniques of high-resolution cryoelectron microscopy (cryo-EM), cellular cryoelectron tomography (cryo-ET), and structure-guided mutagenesis to investigate genome packaging and capsid assembly of bluetongue virus (BTV), a member of the Reoviridae family of dsRNA viruses. A total of eleven assembly states of BTV capsid were captured, with resolutions up to 2.8Å, with most visualized in the host cytoplasm. ATPase VP6 was found underneath the vertices of capsid shell protein VP3 as an RNA-harboring pentamer, facilitating RNA packaging. RNA packaging expands the VP3 shell, which then engages middle- and outer-layer proteins to generate infectious virions. These revealed "duality" characteristics of the BTV assembly mechanism reconcile previous contradictory co-assembly and core-filling models and provide insights into the mysterious RNA packaging and capsid assembly of Reoviridae members and beyond.

Seroprevalence of reproductive and infectious diseases in cattle: the case of Madre de Dios in the Peruvian southeastern tropics.

The objective of this study was to determine the seroprevalence of reproductive and infectious diseases in tropical cattle in the Tambopata and Tahuamanu Provinces in the department of Madre de Dios, Peru. 156 bovines from 7 cattle farms were sampled. These farms used exclusive grazing for food and natural mating for reproduction and did not have sanitary or vaccination programs. The serum of blood samples was subjected to ELISA with commercial kits for the detection of antibodies against Neospora caninum, Mycobacterium avium subsp paratuberculosis (MAP), Leptospira interrogans, pestivirus bovine viral diarrhea virus-1, retrovirus bovine leukemia virus (BLV), orbivirus bluetongue virus (BTV), and herpesvirus bovine herpes virus-1 (BHV). The data were analyzed by means of association tests with χ2 (P < .05) and Spearman rank correlation (P < .05) in the SPSS v.15.0 software (IBM Corp). A low prevalence of antibodies to L interrogans, N caninum, M avium subsp paratuberculosis, bovine viral diarrhea virus-1 was found, but it was high to BTV, BLV, and BHV (100%, 53.85%, and 72.44%, respectively). The presence of BLV and BHV was higher in the Las Piedras District, bovines less than 5 years old, and cattle with breed characteristics of zebu and crossbred (P < .01). In addition, there was a significant correlation between both infections, showing 83.3% of BLV positivity that were also BHV positive (P < .01). The high prevalence of antibodies to BTV, BHV, and BLV could be due to livestock management practices, direct contact with infected animals, and variation of the presence of vectors and natural reservoirs in the context of climate change in the tropics.

Seroprevalence of Bluetongue and Schmallenberg viruses in ruminants in Al-Batinah Governorates, Oman

Bluetongue (BTV) and Schmallenberg viruses (SBV) are the causative agents of Bluetongue and Schmallenberg dis-eases, respectively. Both BTV and SBV are vector-borne viruses that are transmitted mainly by Culicoides (Diptera; Ceratopogo-nidae) and infect do-mestic, wild ruminants, and camelid species. Bluetongue virus be-longs to the genus Orbi-virus, family Reoviridae, whereas Schmallenberg virus belongs to the ge-nus Orthobunyavirus, family Bunyaviridae. In this study, we used en-zyme-linked immuno-sorbent assay (ELISA) to determine the sero-prevalence of both vi-ruses in ruminants in Al-Batinah Gover-norates, Sultanate of Oman. A total of 529 serum samples were randomly collected from 207 sheep, 265 goats, and 57 cattle from five wilayat of Al-Batinah North and Al-Batinah South Governorates. The serum samples were screened for the presence of BTV-specific antibodies against the BTV VP7 protein using ID Screen® Bluetongue Competition (cELISA) and screened for the presence of SBV-specific antibodies against the recombinant SBV nucleoprotein anti-gen using ID Screen® Schmallenberg virus Indirect Mult (iELISA). The overall seropreva-lence of BTV and SBV infections was 69.8% and 44.8%. In cattle, the prevalence of BTV and SBV antibodies was comparatively higher (94.7% and 82.5%) than in goats (83% and 43%) and sheep (45.9% and 36.7%). The high-est BTV seroprevalence was recorded in Nakhal (85.5%), followed by Wadi Al-Maawil (81%), and was lowest in Bar-ka (59.6%). However, the highest seropreva-lence of SBV was ob-served in Wadi Al-Maawil (50%), followed by Barka (48.7%), and lowest in Sohar (34.2%). Overall, the seroprevalence of BTV and SBV in domesticat-ed ruminants was high-er in adults than in young animals. Females showed a higher sero-prevalence of BTV and SBV compared to males. The study pro-vides an update on the epidemiological status of BTV, and to our knowledge, this is the first study on the sero-prevalence of SBV in ruminants in Oman. Future studies are re-quired for the isolation and identification of BTV and SBV along with other potential bio-logical vectors in Oman.