Sero-epidemiology of bluetongue in ruminants raised on private holdings in North-Western Pakistan.

This study investigated the sero-epidemiology of bluetongue in ruminants in North-Western Pakistan. A total of 3,173 serum samples were collected from small (n = 1,651) and large (n = 1,522) ruminants being reared by farmers in 14 districts. Antibodies to bluetongue virus (BTV) were detected using competitive ELISA. The overall prevalence of BTV antibodies was 65%. A significant association (P < 0.05) between the prevalence of BTV antibodies and the risk factors including sex, species, age, area, husbandry practices and breed was shown by univariate analysis. In multivariate analysis, the seroprevalence was 6.5 (95% CL = 3.7-11.4), 5.9 (95% CL = 3.8-9.4) and 2.4 (95% CL = 1.5-3.7) times higher in buffaloes, cattle and goats than sheep, respectively. The seroprevalence was 1.4 (95% CL = 1.1-1.7) times higher in local breeds than in cross/exotic breeds. The seroprevalence was 1.6 (95% CL = 1.1 to 2.3) times higher in sedentary animals than in nomadic animals. The seroprevalence was significantly associated with age. Further work is required to determine the BTV serotypes prevalent in the study area for effective control of the disease.

Bluetongue Virus Serotype 3 and Schmallenberg Virus in Culicoides Biting Midges, Western Germany, 2023.

In October 2023, bluetongue virus serotype 3 (BTV-3) emerged in Germany, where Schmallenberg virus is enzootic. We detected BTV-3 in 1 pool of Culicoides biting midges collected at the time ruminant infections were reported. Schmallenberg virus was found in many vector pools. Vector trapping and analysis could elucidate viral spread.

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.

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

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 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. 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.

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.

Reemerging/Notifiable Diseases to Watch.

Reemerging and notifiable diseases of cattle and bison continue to pose potential risks to their health and lives and affecting production and the livelihoods of producers. It is essential to understand the clinical presentation of these diseases to watch for possible incursions and infections and to immediately report your suspicions to your State and Federal Animal Health Officials. Three of these reemerging and notifiable diseases of cattle and bison, malignant catarrhal fever, bluetongue virus, and New World screwworm, are presented in this article for increased awareness to consider as a differential if examinations present suggestive clinical signs.

Evidence of Active Orbivirus Transmission in 2016 in Kansas and Nebraska.

Retrospective serological and case diagnostic data of endemic bluetongue virus (BTV) and epizootic hemorrhagic disease virus (EHDV) provide evidence of viral transmission among livestock and wildlife from 2016 in Kansas and Nebraska. Serological testing of mature cattle in nine distinct regional zones of Kansas revealed 76% to 100% had detectable antibodies to BTV and/or EHDV. Specimens tested in the Kansas Veterinary Diagnostic Laboratory (55 submissions) were 51% test positive for antibodies to BTV and/or EHDV. Specimens tested in the Nebraska Veterinary Diagnostic Center (283 submissions) were 25% test positive for antibodies to BTV and/or EHDV. Low disease incidence in white-tailed deer and other susceptible wild ungulates was observed during 2016. However, there were no confirmed reports of disease in livestock in either state. The reasons for emergence of significant clinical disease in livestock and wildlife populations remain undefined.

Specific T-cell subsets have a role in anti-viral immunity and pathogenesis but not viral dynamics or onwards vector transmission of an important livestock arbovirus.

Introduction: Bluetongue virus (BTV) is an arthropod-borne Orbivirus that is almost solely transmitted by Culicoides 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 Culicoides vector is defined in unprecedented detail for the first time, using an in vivo 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 Culicoides. 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.

First molecular evidence of potential Culicoides vectors implicated in bluetongue virus transmission in Morocco.

BACKGROUND: Bluetongue is a non-contagious viral disease that affects both domestic and wild ruminants. It is transmitted primarily by small hematophagous Diptera belonging to the genus Culicoides (Diptera: Ceratopogonidae). The current study represents the first molecular investigation into the potential role of Culicoides imicola, Culicoides paolae, Culicoides newsteadi, Culicoides spp., and Culicoides circumscriptus as bluetongue virus (BTV) vectors in Morocco. Additionally, the study aimed to evaluate the vectorial activity of midges during the survey seasons. METHODS: Parous females of these species were captured from several regions of Morocco (6 out of 12) from 2018 to 2021 using Onderstepoort Veterinary Institute (OVI) traps. A total of 2003 parous female specimens were grouped into 55 batches. The midge body of each batch was dissected into three regions (head, thorax, and abdomen), and these regions were analyzed separately using reverse transcription quantitative polymerase chain reaction (RT-qPCR). RESULTS: BTV RNA was detected in 45 out of the 55 batches tested, indicating a positivity rate of 81.8%. The RT-qPCR-positive pools of the studied Culicoides species exhibited high levels of BTV positivity in each body part (head, thorax, and abdomen), confirming the successful replication of the virus within midge bodies. The BTV circulation was substantial across all three survey seasons (spring, summer, and autumn). High infection rates, calculated using the minimum infection rate (MIR) and maximum likelihood estimation (MLE), were observed during the collection seasons, particularly in autumn and spring, and for all investigated Culicoides species, most notably for C. imicola and C. newsteadi. These increased infection rates underscore the significant risk of Culicoides transmitting the BTV in Morocco. CONCLUSIONS: The detection of BTV positivity in Culicoides spp. (lacking wing spots that allow their differentiation according to morphological identification keys) suggested that other Culicoides species are competent for BTV transmission in Morocco. The study results indicated, for the first time at the molecular level, that C. imicola and C. newsteadi are the primary potential vectors of BTV in Morocco and that C. paolae and C. circumscriptus are strongly implicated in the propagation of bluetongue at the national level.

Seven-year prospective study on yearly incidence of Orbivirus infection of captive white-tailed deer and potential Culicoides vectors.

Bluetongue virus (BTV) and epizootic hemorrhagic disease virus (EHDV) are arthropod-borne viruses that are transmitted by biting midges in the genus Culicoides (Diptera: Ceratopogonidae) and can cause hemorrhagic disease in certain ruminants. The objectives of this study were to measure the incidence of BTV and EHDV infections in captive white-tailed deer herd as well as tissues and corresponding presence of Culicoides midges at a location near Clinton, LA. During a 7-yr study with yearly outbreaks of hemorrhagic disease in the deer herd, 15 species of Culicoides were captured using Centers for Disease Control (CDC) black light traps. Reverse transcriptase quantitative polymerase chain reaction (PCR) was performed to screen for BTV and EHDV in pools of midges and tissues of deer. From 2012 to 2018, 1,711 pools of midges representing 24,859 specimens were tested, and specimens from 5 of the 15 collected species (Culicoides debilipalpis, Culicoides stellifer, Culicoides venustus, Culicoides haematopotus, and Culicoides crepuscularis) were found to be PCR positive for BTV and EHDV. Most of the BTV-positive pools of biting midges were from specimens of C. debilipalpis and C. stellifer, and most of the EHDV-positive pools were from specimens of C. venustus and C. stellifer. During the 7-yr period, 112 white-tailed deer that died at the study location were PCR positive for BTV or EHDV: detected BTV serotypes were 10 and 12 and EHDV serotypes were 1, 2, and 6. There was a significant increase in BTV/EHDV antibody prevalence in white-tailed deer during the study; antibody-positive rates increased from 15% to 78% in the deer herd of approximately 100 animals.

Detection, Characterization and Sequencing of BTV Serotypes Circulating in Cuba in 2022.

In Cuba, despite a high sero-prevalence of bluetongue virus (BTV), circulating serotypes remain unknown. The aim of this study was to identify circulating BTV serotypes in farms throughout the western region of Cuba. Blood samples were collected from 200 young cattle and sheep between May and July 2022 for virological analyses (PCR, viral isolation and virus neutralization) and genome sequencing. The results confirmed viral circulation, with viro-prevalence of 25% for BTV. The virus was isolated from 18 blood samples and twelve BTV serotypes were identified by sequencing RT-PCR products targeting the segment 2 of the BTV genome (BTV-1, 2, 3, 6, 10, 12, 13, 17, 18, 19, 22 and 24). Finally, the full genome sequences of 17 Cuban BTV isolates were recovered using a Sequence Independent Single Primer Amplification (SISPA) approach combined to MinION Oxford Nanopore sequencing technology. All together, these results highlight the co-circulation of a wide diversity of BTV serotypes in a quite restricted area and emphasize the need for entomological and livestock surveillance, particularly in light of recent changes in the global distribution and nature of BTV infections.

Bluetongue virus seroprevalence and risk factor analysis in cattle and water buffalo in southern Italy (Campania region).

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.

Preliminary investigation reveals novel pathological consequences of bluetongue virus-1 infection in the endocrine glands of pregnant Indian sheep.

Bluetongue virus (BTV), a major peril to the sheep industry, infects a wide range of the cells in the infected animals including mononuclear, dendritic and epithelial cells. However, little is known about its tropism for the secretory epithelial cells of endocrine glands and the pathogenesis it induces. The aim of the study was to assess the BTV load, antigen distribution in the tissue of the pituitary, thyroid as well as adrenal glands and associated histopathological consequences. BTV antigens were localized using immunohistochemistry in the thyroid's epithelial cells, zona fasciculata and zona reticularis cells and the anterior pituitary epithelial cells. The real-time PCR portrayed the high viral load in adrenals at 7th days postinoculation (DPI) and in thyroid and pituitary glands at 15th DPI. Serum examination revealed variation in the T-3 and T-4 of infected animals in comparison to the control group. Caspase-3 immunolocalization revealed BTV-1 induces apoptosis in the affected cells of endocrine gland of infected animals. Further, this study signifies the tropism of BTV in the novel sites (endocrine glands) of the host that might be one of the reasons for the poor performance of infected animals.

Clinical presentation, medical management, and outcomes in 35 hospitalized sheep diagnosed with bluetongue virus 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.

Bluetongue disease in sheep in New South Wales - April 2023.

In 2016, bluetongue virus (BTV), serotype 16 (BTV-16), was detected in New South Wales (NSW) in sentinel cattle for the first time. Over the next 6 years, BTV-16 has been detected regularly and over an increasing area of the BTV zone in NSW. In April 2023, disease was reported in sheep on two farms on the Northern Tablelands of NSW. The consistent clinical signs included reduced exercise tolerance, facial swelling, serous nasal discharges with encrustation of the nasal plane, subcutaneous oedema of the neck and brisket and variable congestion of the coronary band. Affected sheep were mainly mature ewes and rams, with an estimated morbidity of 20% over a period of 6-8 weeks. Although there were several unexpected deaths, no veterinary examination was sought. Predominantly BTV-16 RNA was detected in sick sheep, with an incidence of infection of approximately 40% in a cross section of one flock. These events represent the first confirmation of disease due to bluetongue virus in NSW. As these cases occurred in a region with a high density of sheep, if there is ongoing transmission of BTV-16 during subsequent summers, further disease might be expected.