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Viruses Feb 2024Bluetongue virus (BTV) is a segmented, double-stranded RNA orbivirus listed by the World Organization for Animal Health and transmitted by biting midges. Segmented...
Bluetongue virus (BTV) is a segmented, double-stranded RNA orbivirus listed by the World Organization for Animal Health and transmitted by biting midges. Segmented viruses can reassort, which facilitates rapid and important genotypic changes. Our study evaluated reassortment in midges coinfected with different ratios of BTV-10 and BTV-17. Midges were fed blood containing BTV-10, BTV-17, or a combination of both serotypes at 90:10, 75:25, 50:50, 25:75, or 10:90 ratios. Midges were collected every other day and tested for infection using pan BTV and (housekeeping gene) qRT-PCR. A curve was fit to the ∆Ct values (pan BTV Ct- Ct) for each experimental group. On day 10, the midges were processed for BTV plaque isolation. Genotypes of the plaques were determined by next-generation sequencing. Pairwise comparison of ∆Ct curves demonstrated no differences in viral RNA levels between coinfected treatment groups. Plaque genotyping indicated that most plaques fully aligned with one of the parental strains; however, reassortants were detected, and in the 75:25 pool, most plaques were reassortant. Reassortant prevalence may be maximized upon the occurrence of reassortant genotypes that can outcompete the parental genotypes. BTV reassortment and resulting biological consequences are important elements to understanding orbivirus emergence and evolution.
Topics: Animals; Serogroup; Bluetongue virus; Ceratopogonidae; Coinfection; Genotype
PubMed: 38400016
DOI: 10.3390/v16020240 -
Journal of Thermal Biology Jan 2024Biting midges of the genus Culicoides (Diptera: Ceratopogonidae) are hematophagous insects, and some species can transmit a plethora of pathogens, e.g., bluetongue virus...
Biting midges of the genus Culicoides (Diptera: Ceratopogonidae) are hematophagous insects, and some species can transmit a plethora of pathogens, e.g., bluetongue virus and African horse sickness virus, that mainly affect animals. The transmission of vector-borne pathogens is strongly temperature dependent, and recent studies pointed to the importance of including microclimatic data when modelling disease spread. However, little is known about the preferred temperature of biting midges. The present study addressed the thermal selection of field-caught Culicoides with two experiments. In a laboratory setup, sugar-fed or blood-fed midges were video tracked for 15 min while moving inside a 60 × 30 × 4 cm setup with a 15-25 °C temperature gradient. Culicoides spent over double the time in the coldest zone of the setup compared to the warmest one. This cold selection was significantly stronger for sugar-fed individuals. Calculated preferred temperatures were 18.3 °C and 18.9 °C for sugar-fed and blood-fed Culicoides, respectively. The effect of temperature on walking speed was significant but weak, indicating that their skewed distribution results from preference and not cold trapping. A second experiment consisted of a two-way-choice-setup, performed in a 90 × 45 × 45 cm net cage, placed outdoors in a sheltered environment. Two UV LED CDC traps were placed inside the setup, and a mean temperature difference of 2.2 °C was created between the two traps. Hundred-fifty Culicoides were released per experiment. Recapture rates were negatively correlated with ambient temperature and were on average three times higher in the cooled trap. The higher prevalence of biting midges in cooler environments influences fitness and ability to transmit pathogens and should be considered in models that predict Culicoides disease transmission.
Topics: Humans; Animals; Ceratopogonidae; Insect Vectors; African Horse Sickness Virus; Environment; Sugars
PubMed: 38244238
DOI: 10.1016/j.jtherbio.2024.103783 -
Journal of Invertebrate Pathology Jun 2024Insects have a rich diversity of RNA viruses that can either cause acute infections or persist in host populations without visible symptoms. The melon fly, Zeugodacus...
Insects have a rich diversity of RNA viruses that can either cause acute infections or persist in host populations without visible symptoms. The melon fly, Zeugodacus cucurbitae (Tephritidae) causes substantial economic losses through infestation of diverse cucurbit and other crops. Of Indomalayan origin, it is now established in many tropical regions of the world. The virome diversity of Z. cucurbitae is largely unknown across large parts of its distribution, including the Indian subcontinent. We have analysed three transcriptomes each of one field-collected and one laboratory-reared Z. cucurbitae population from Bangalore (India) and discovered genomes of ten putative RNA viruses: two sigmaviruses, one chimbavirus, one cripavirus, one noda-like virus, one nora virus, one orbivirus, one partiti-like virus, one sobemovirus and one toti-like virus. Analysis of the only available host genome of a Hawaiian Z. cucurbitae population did not detect host genome integration of the detected viruses. While all ten viruses were found in the Bangalore field population only seven were detected in the laboratory population, indicating that these seven may cause persistent covert infections. Using virus-specific RNA-dependent RNA polymerase gene primers, we detected nine of the RNA viruses with an overall low variant diversity in some but not all individual flies from four out of five Indian regions. We then screened 39 transcriptomes of Z. cucurbitae laboratory populations from eastern Asia (Guangdong, Hainan, Taiwan) and the Pacific region (Hawaii), and detected seven of the ten virus genomes. We found additional genomes of a picorna-like virus and a negev-like virus. Hawaii as the only tested population from the fly's invasive range only had one virus. Our study provides evidence of new and high RNA virus diversity in Indian populations within the original range of Z. cucurbitae, as well as the presence of persistent covert infections in laboratory populations. It builds the basis for future research of tephritid-associated RNA viruses, including their host effects, epidemiology and application potential in biological control.
Topics: Animals; RNA Viruses; Tephritidae; India; Genome, Viral; Transcriptome; Virome
PubMed: 38679365
DOI: 10.1016/j.jip.2024.108117 -
Journal of Veterinary Internal Medicine 2024There is only limited information on the clinical presentation, medical management, and outcomes of hospitalized sheep diagnosed with bluetongue virus (BTV) disease.
BACKGROUND
There is only limited information on the clinical presentation, medical management, and outcomes of hospitalized sheep diagnosed with bluetongue virus (BTV) disease.
OBJECTIVES
To describe the signalment, history, clinical signs, clinicopathological findings, medical management, and clinical outcomes of sheep diagnosed with BTV disease.
ANIMALS
Thirty-five hospitalized sheep with BTV disease.
METHODS
Retrospective case series. Medical records from 1989 to 2021 were evaluated. History, signalment, clinical signs, laboratory test results, treatments, and outcomes were recorded.
RESULTS
BTV disease was diagnosed from July to December, with a peak proportion (43%; 15/35) of diagnoses recorded in October. Pyrexia and anorexia, respiratory disease, vasculitis, coronitis and lameness, and ulcerative mucosal lesions were present in 71%, 71%, 66%, 49%, and 22% of sheep, respectively. BTV serotypes 10, 11, 13, and 17 were identified, with serotype 17 (75%) being the most frequent. Management of cases included administration of antimicrobials (89%), anti-inflammatories (77%), IV fluids (60%), vitamins (20%), proton-pump inhibitors (14%), diuretics (9%), and antioxidants (9%). Six ewes were pregnant on presentation, but none aborted. Six (17%) sheep died or were euthanized because of clinical deterioration, whereas 83% were discharged.
CONCLUSIONS AND CLINICAL IMPORTANCE
The proportion of sheep that survived BTV disease after treatment was relatively high. Serotyping of BTV is recommended because of the mismatch between frequently identified serotypes and the serotype present in the vaccine.
Topics: Pregnancy; Sheep; Animals; Female; Bluetongue virus; Retrospective Studies; Bluetongue; Serogroup; Sheep Diseases
PubMed: 38038181
DOI: 10.1111/jvim.16944 -
Viruses Apr 2024A 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...
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.
Topics: Animals; Bluetongue; Bluetongue virus; Netherlands; Sheep; Serogroup; Cattle; Epidemics; Cattle Diseases
PubMed: 38675966
DOI: 10.3390/v16040625 -
Veterinary Research Communications Feb 2024Bluetongue is an arthropod-borne viral infection that is notifiable in several countries and causes significant economic losses and major concerns for ruminant trade. In...
Bluetongue is an arthropod-borne viral infection that is notifiable in several countries and causes significant economic losses and major concerns for ruminant trade. In this study, we investigated bluetongue 1seroprevalence in the Campania region, southern Italy, in cattle and buffalo populations, and assessed which factors were correlated with a high risk of exposure. The infection was widespread, as evidenced by the high individual (43.6%) and herd prevalence (85.4%). The highest prevalence was found in adult animals. Among the climatic factors analyzed, average temperature played a prominent role, being capable of affecting the probability of being positive for this infection. Surprisingly, exposure to Schmallenberg virus did not predispose animals to be positive for bluetongue virus, even though these infections share the same vector (Culicoides). Our data, consistent with those in the literature, suggest the transversal spread of bluetongue virus in the Mediterranean area, and indicate a limited co-exposure rate between Bluetongue and Schmallenberg viruses.
Topics: Sheep; Animals; Cattle; Buffaloes; Bluetongue; Bluetongue virus; Seroepidemiologic Studies; Italy; Sheep Diseases
PubMed: 37682447
DOI: 10.1007/s11259-023-10215-w -
Viruses May 2024(1) Background: Epizootic hemorrhagic disease virus (EHDV) and bluetongue virus (BTV) are orbiviruses that cause hemorrhagic disease (HD) with significant economic and...
(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 () are particularly susceptible to these viruses and are a frequent blood meal host for various species of biting midges (Diptera: Ceratopogonidae) that transmit orbiviruses. The species of 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, and , and one species, , 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 and . 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 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.
Topics: Animals; Ceratopogonidae; Hemorrhagic Disease Virus, Epizootic; Deer; Insect Vectors; Bluetongue virus; Animals, Wild; Reoviridae Infections; Ecosystem; Seasons; Farms; Birds
PubMed: 38793647
DOI: 10.3390/v16050766 -
Viruses Mar 2024The African horse sickness virus (AHSV) belongs to the Genus Orbivirus, family Sedoreoviridae, and nine serotypes of the virus have been described to date. The AHSV...
Development and Validation of Three Triplex Real-Time RT-PCR Assays for Typing African Horse Sickness Virus: Utility for Disease Control and Other Laboratory Applications.
The African horse sickness virus (AHSV) belongs to the Genus Orbivirus, family Sedoreoviridae, and nine serotypes of the virus have been described to date. The AHSV genome is composed of ten linear segments of double-stranded (ds) RNA, numbered in decreasing size order (Seg-1 to Seg-10). Genome segment 2 (Seg-2) encodes outer-capsid protein VP2, the most variable AHSV protein and the primary target for neutralizing antibodies. Consequently, Seg-2 determines the identity of the virus serotype. An African horse sickness (AHS) outbreak in an AHS-free status country requires identifying the serotype as soon as possible to implement a serotype-specific vaccination program. Considering that nowadays 'polyvalent live attenuated' is the only commercially available vaccination strategy to control the disease, field and vaccine strains of different serotypes could co-circulate. Additionally, in AHS-endemic countries, more than one serotype is often circulating at the same time. Therefore, a strategy to rapidly determine the virus serotype in an AHS-positive sample is strongly recommended in both epidemiological situations. The main objective of this study is to describe the development and validation of three triplex real-time RT-PCR (rRT-PCR) methods for rapid AHSV serotype detection. Samples from recent AHS outbreaks in Kenia (2015-2017), Thailand (2020), and Nigeria (2023), and from the AHS outbreak in Spain (1987-1990), were included in the study for the validation of these methods.
Topics: Animals; Horses; African Horse Sickness Virus; Reverse Transcriptase Polymerase Chain Reaction; African Horse Sickness; Orbivirus; Antibodies, Neutralizing; Viral Vaccines
PubMed: 38543834
DOI: 10.3390/v16030470 -
Frontiers in Immunology 2024Bluetongue virus (BTV) is an arthropod-borne that is almost solely transmitted by biting midges and causes a globally important haemorrhagic disease, bluetongue (BT),...
INTRODUCTION
Bluetongue virus (BTV) is an arthropod-borne that is almost solely transmitted by biting midges and causes a globally important haemorrhagic disease, bluetongue (BT), in susceptible ruminants. Infection with BTV is characterised by immunosuppression and substantial lymphopenia at peak viraemia in the host.
METHODS
In this study, the role of cell-mediated immunity and specific T-cell subsets in BTV pathogenesis, clinical outcome, viral dynamics, immune protection, and onwards transmission to a susceptible vector is defined in unprecedented detail for the first time, using an arboviral infection model system that closely mirrors natural infection and transmission of BTV. Individual circulating CD4, CD8, or WC1 γδ T-cell subsets in sheep were depleted through the administration of specific monoclonal antibodies.
RESULTS
The absence of cytotoxic CD8 T cells was consistently associated with less severe clinical signs of BT, whilst the absence of CD4 and WC1 γδ T cells both resulted in an increased clinical severity. The absence of CD4 T cells also impaired both a timely protective neutralising antibody response and the production of IgG antibodies targeting BTV non-structural protein, NS2, highlighting that the CD4 T-cell subset is important for a timely protective immune response. T cells did not influence viral replication characteristics, including onset/dynamics of viraemia, shedding, or onwards transmission of BTV to . We also highlight differences in T-cell dependency for the generation of immunoglobulin subclasses targeting BTV NS2 and the structural protein, VP7.
DISCUSSION
This study identifies a diverse repertoire of T-cell functions during BTV infection in sheep, particularly in inducing specific anti-viral immune responses and disease manifestation, and will support more effective vaccination strategies.
Topics: Sheep; Animals; Livestock; Viremia; Arboviruses; CD8-Positive T-Lymphocytes; Ruminants; T-Lymphocyte Subsets; Bluetongue virus; Bluetongue; Ceratopogonidae
PubMed: 38357545
DOI: 10.3389/fimmu.2024.1328820 -
Parasites & Vectors May 2024As 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...
BACKGROUND
As 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.
METHODS
The diel host-seeking activity of C. sonorensis was studied on a California dairy over 3 years using a time-segregated trap baited with CO. 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.
RESULTS
Host-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.
CONCLUSIONS
This 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.
Topics: Animals; Ceratopogonidae; Seasons; California; Female; Temperature; Dairying; Insect Vectors; Host-Seeking Behavior; Cattle; Environment; Bluetongue virus; Bluetongue
PubMed: 38730488
DOI: 10.1186/s13071-024-06290-w