Bluetongue Virus In Cattle Research Articles

Exposure to multiple pathogens - serological evidence for Rift Valley fever virus, Coxiella burnetii, Bluetongue virus and Brucella spp. in cattle, sheep and goat in Mali.

An important problem for livestock production in Mali is occurrence of several infectious diseases. A particular challenge for control of pathogens that affect different species, especially in a system with mixed herds with cattle, sheep and goats. Therefore, this study aimed to investigate co-exposure with Rift Valley fever virus (RVFV), Coxiella burnetii, Bluetongue virus (BTV) and Brucella spp. in different livestock species in mixed herds. With the exception of BTV these pathogens are also zoonotic. A retrospective assessment was carried out on a biobank of sera of cattle and small ruminants collected from Sikasso and Mopti regions. Nine hundred and twelve samples from cattle (n = 304), sheep (n = 318) and goat (n = 290) were screened. Serology tests were conducted using commercial kits as per the protocol of the manufacturers. Sero-prevalence for RVFV was 12.8% (Confidence Interval 95%: 9.3–17.1%); 4.7% (2.7–7.7%) and 3.1% (1.4–5.8%) in cattle, sheep and goat respectively. For Coxiella burnetii, the sero-prevalence was 55.3% (49.5–60.9%), 22.6% (18.2–27.6%), and 16.9% (12.8–21.7%); in cattle, sheep and goat respectively; and for BTV sero-prevalence was 88.8% (84.72–92.13%), 51.6% (45.9–57.2%), 56.2% (50.3–62.0%) in cattle, sheep in goat respectively. Brucella sp. had the lowest sero-prevalence and was only detected in cattle and sheep. Regional differences were observed with sero-prevalence of Coxiella burnetii in sheep and goat with BTV in goat being significantly higher in Sikasso than in Mopti (p<0.001). Evidence of exposure to two pathogens in the same animal was most common for the combination Coxiella burnetii and BTV in cattle (51.6%), followed by sheep (17.0%) and goat (15.5%). Considering the scarcity of disease occurrence and epidemiological data in most sub-saharan countries including Mali, this multi-pathogen survey provides important evidence that cattle, sheep and goat are exposed to pathogens that may negatively impact productivity and pose a risk for public health. The results from this study highlight the urgent need for a better understanding of pathogen diversity and their impact on human and animal health in order to minimize resulting risks. Given that some of the pathogens investigated here are zoonotic, establishment of One-Health surveillance system to monitor disease in animals and people is warranted. Therefore, intersectoral collaboration is recommended.

Risk-based surveillance for bluetongue virus in cattle on the south coast of England in 2017 and 2018

BackgroundBluetongue (BT) is a viral disease of ruminants and camelids which can have a significant impact on animal health and welfare and cause severe economic loss. The UK has been...

Reassortment of bluetongue virus vaccine serotypes in cattle.

Bluetongue is primarily a disease of sheep in South Africa, while cattle and goats are mostly subclinically infected. The viraemia of bluetongue virus in cattle lasts much longer than in sheep and the role of cattle in the epidemiology of bluetongue in South Africa is poorly understood. Bluetongue virus has a segmented double-stranded ribonucleic acid genome and reassortment of genomes is a common feature. The aim of the study was to investigate whether reassortment occurs between vaccine and field strains when simultaneously administered to cattle. Six cattle between the ages of 6 and 12 months were infected with five strains of modified live vaccine bluetongue virus and a virulent field isolate of bluetongue virus 4. Blood samples were subsequently collected daily from these animals from day 1 to day 39 post-inoculation. Viruses were directly isolated during viraemia from the buffy coat on Vero cells using the plaque forming unit method. Analysis of plaques indicated that no reassortants between virulent field and vaccine strains occurred and the virulent bluetongue virus 4 was identified as the predominant virus strain. However, a reassortant virus between two bluetongue virus vaccine strains was isolated from the buffy coat. Whole genome sequences from the vaccine viruses were compared to the suspected reassortant and it was found that segment 8 exchanged between the bluetongue virus 8 and bluetongue virus 9 vaccine strains. The use of the live-attenuated bluetongue virus multivalent vaccine in South Africa causes circulation of different vaccine serotypes in Culicoides spp. and susceptible hosts and cattle might provide the ideal host for reassortment to occur.

Reassortment of bluetongue virus vaccine serotypes in cattle

Bluetongue is primarily a disease of sheep in South Africa, while cattle and goats are mostly subclinically infected. The viraemia of bluetongue virus in cattle lasts much longer than in sheep and the role of cattle in the epidemiology of bluetongue in South Africa is poorly understood. Bluetongue virus has a segmented double-stranded ribonucleic acid genome and reassortment of genomes is a common feature. The aim of the study was to investigate whether reassortment occurs between vaccine and field strains when simultaneously administered to cattle. Six cattle between the ages of 6 and 12 months were infected with five strains of modified live vaccine bluetongue virus and a virulent field isolate of bluetongue virus 4. Blood samples were subsequently collected daily from these animals from day 1 to day 39 post-inoculation. Viruses were directly isolated during viraemia from the buffy coat on Vero cells using the plaque forming unit method. Analysis of plaques indicated that no reassortants between virulent field and vaccine strains occurred and the virulent bluetongue virus 4 was identified as the predominant virus strain. However, a reassortant virus between two bluetongue virus vaccine strains was isolated from the buffy coat. Whole genome sequences from the vaccine viruses were compared to the suspected reassortant and it was found that segment 8 exchanged between the bluetongue virus 8 and bluetongue virus 9 vaccine strains. The use of the live-attenuated bluetongue virus multivalent vaccine in South Africa causes circulation of different vaccine serotypes in Culicoides spp. and susceptible hosts and cattle might provide the ideal host for reassortment to occur.

Prevalence and risk factors for bluetongue in the State of São Paulo, Brazil.

Bluetongue (BT), caused by Bluetongue virus (BTV), is a disease that affects ruminants such as cattle, sheep, goats and deer. BTV is transmitted by female midges of the genus Culicoides. In Brazil, information on the prevalence of BTV in cattle is limited, so the objective of this work was to identify BTV serotypes in cattle. The State of São Paulo was divided into seven cattle‐producing regions, and in each of them, 300 cattle farms were randomly selected. One animal from each farm (out of a total of 1,598 farms) was selected and its sera tested by virus neutralization technique against BTV serotypes (1–24 and 26) for determining antibody titre. Moreover, for each sampled farm, an epidemiological questionnaire was submitted to verify the type of cattle production and the zootechnical and sanitary practices carried out, which could be associated with a higher risk of BTV infection. In this study, antibodies (percentage, [95% confidence interval]) were identified against 11 serotypes: BTV‐1 (22.15%, [15.72–27.92]), BTV‐2 (31.03%, [26.65–37.98]), BTV‐3 (18.96%, [12.42–24.90]), BTV‐4 (24.90% [19.41–29.12]), BTV‐9 (6.82%, [1.45–11.72]), BTV‐12 (7.50%, [2.82–12.51]), BTV‐17 (23.90%, [17.35–29.35]), BTV‐19 (10.20%, [4.62–5.56]), BTV‐21 (30.66%, [25.00–36.00]), BTV‐22 (12.14%, [5.91–18.55]), BTV‐26 (57.00%, [51.41–63.59]). In this study, for the first time in Brazil serological evidence of the presence of serotypes BTV‐2, BTV‐9, BTV‐21 and BTV‐26 is reported. The variable ‘new cattle entering herd’ was considered a risk factor for the occurrence of infection (OR = 2.183, 95% CI = 1.6–2.9).

Detection in and circulation of Bluetongue virus among domestic ruminants in Madagascar

So far, no published data was available concerning the circulation of Bluetongue virus (BTV) in Madagascar. During a survey on Rift Valley Fever, we were able to detect a virus belonging to BTV. Therefore, we conducted a study aiming at characterizing molecularly the BTV isolated and assess the importance of circulation of BTV in Madagascar. A total of 4393 sera from ruminants selected randomly by stratification and sampled in 30 districts of Madagascar were tested for BTV. Moreover, 175 cattle were followed during 11 months. Phylogenetic analyses were performed from virus isolated from unfed pools of mosquitoes.Overall, the estimated mean seroprevalence of infection at the national level was 95.9% (95% CI: [95.2–96.5]) in cattle and 83.7% (95% CI: [81.4–85.9]) in small ruminants. Estimation of incidence rate was 54 per 100 cattle-years assuming that the incidence rate is constant all year along. Phylogenetic analyses revealed that BTV detected belong to serotype 2.In conclusion, our results showed that BTV is endemic in Madagascar and highly prevalent among cattle. In our study we did not work on the vector involved in transmission of BTV in cattle. Thus, research should be conducted to better describe epidemiology of BTV in Madagascar including vectors and assess economic impact of the disease associated to BTV infections.

Scaling from challenge experiments to the field: Quantifying the impact of vaccination on the transmission of bluetongue virus serotype 8

Bluetongue (BT) is an economically important disease of ruminants caused by bluetongue virus (BTV) and transmitted by Culicoides biting midges. The most practical and effective way to protect susceptible animals against BTV is by vaccination. Data from challenge studies in calves and sheep conducted by Intervet International b.v., in particular, presence of viral RNA in the blood of challenged animals, were used to estimate vaccine efficacy. The results of the challenge studies for calves indicated that vaccination is likely to reduce the basic reproduction number (R0) for BTV in cattle to below one (i.e. prevent major outbreaks within a holding) and that this reduction is robust to uncertainty in the model parameters. Sensitivity analysis showed that the whether or not vaccination is predicted to reduce R0 to below one depended on the following assumptions: (i) whether “doubtful” results from the challenge studies are treated as negative or positive; (ii) whether or not the probability of transmission from host to vector is reduced by vaccination; and (iii) whether the extrinsic incubation period follows a realistic gamma distribution or the more commonly used exponential distribution. For sheep, all but one of the vaccinated animals were protected and, consequently, vaccination will consistently reduce R0 in sheep to below one. Using a stochastic spatial model for the spread of BTV in Great Britain (GB), vaccination was predicted to reduce both the incidence of disease and spatial spread in simulated BTV outbreaks in GB, in both reactive vaccination strategies and when an incursion occurred into a previously vaccinated population.

Clinical syndromes associated with the circulation of multiple serotypes of bluetongue virus in dairy cattle in Israel

From 2008 to 2011, seven distinct bluetongue virus (BTV) serotypes (BTV-2, BTV-4, BTV-5, BTV-8, BTV-15, BTV-16 and BTV-24) have been identified to be circulating in diseased sheep and cattle in...

The presence of bluetongue virus serotype 8 RNA in Belgian cattle since 2008

After a short winter break, bluetongue virus serotype 8 was responsible in 2007 for a large-scale epidemic among ruminant populations in Western Europe. Little is known about the mechanisms allowing the virus to survive winter conditions. A yearly mass vaccination of cattle and sheep started in spring 2008, which was recognized as successful in terms of clinical protection, but occult circulation of the bluetongue virus has not been adequately addressed. We studied the carriage of bluetongue RNA in the spleen of cattle in the vector-free period and the circulation of bluetongue virus in cattle populations in Belgium since the introduction of vaccination programmes. Overall, the results presented here show evidence for the long-term carriage of bluetongue virus RNA in the spleen of cattle and demonstrated a low but significant circulation and transplacental transmission of bluetongue virus in Belgian cattle in 2009, with apparent disappearance in 2010.

Mise au point de nouvelles techniques de diagnostic pour les maladies à orbivirus chez les animaux domestiques et sauvages

The recent emergence and spread of bluetongue virus (BTV) across the whole of Europe suggests that other orbiviruses could also emerge to threaten livestock species and wildlife popula­tions in Europe and other parts of the world. The genus Orbivirus is the largest within the family Reoviridae, containing 22 virus species, as well as 14 unclassified orbiviruses. The orbiviruses are transmitted primarily by arthropod vectors (e.g. Culicoides, mosquitoes or ticks) and several are associated with severe and economically important diseases of livestock, including BTV in cattle and sheep, African horse sickness virus (AHSV), equine encephalosis virus (EEV) and Peruvian horse sickness virus (PHSV) in equids, as well as epizootic haemorrhagic disease virus (EHDV) in wild ungulates or cattle. Recent incursions of BTV in Europe, Southeastern USA, Australia and Asia, EHDV in North Africa, the Middle East and the Mediterranean region, AHSV in sub-Saharan Africa, and EEV in Israel and Gambia, indicate a need for the development of faster, more sensitive and more reliable diagnostic assays. These are required to detect and identify rapidly the viruses and virus types involved, monitor their incidence and movement, and identify infected animals. The Orbivirus genome is composed of 10 linear segments of double-stranded ribonucleic acid (dsRNA), each segment coding for at least one viral protein. The outer capsid proteins VP2 and VP5 are situated on or near the surface of the virus particle and are more variable than components of the virus core, or the non-structural proteins. VP2 (encoded by Seg- 2) is the outermost of the BTV capsid proteins and represents the primary target antigen for neutralising antibodies, and hence Seg-2 is a target for the development of type-specific nucleic-acid-based diagnostic assays. In contrast, the genome segments coding for protein components of the virus core and/or the non-structural proteins can be used as targets for development of serogroup (virus-species) specific, reverse transcription - poly­merase chain reaction (RT-PCR) based diagnostic assays. Virus species-specific and type-specific conventional (gel based) RT-PCR diagnostic assays, for the detection, identification and typing of some of these viruses (BTV, EHDV and AHSV), have been developed using the sequence data for segments 7 and 2, respectively. Initial evaluation studies indicate that these assays are reliable, specific, do not cross-react with related orbiviruses (group/species specific) or with related types (type specific). Although they are labour intensive, the results obtained can be confirmed by sequence analyses of the resulting complemen­tary deoxyribonucleic acid complementary (c) DNA amplicons, and phylogenetic comparisons to determine the strain of virus involved. However, conventional RT-PCR assays are prone to cross-contamination, potentially leading to false positive results. The authors also describe group-specific real-time RT-PCR assays that use a ‘closed-tube’ format, which are therefore less suscep­tible to cross-contamination. These assays target the conserved genome segment 9, or genome segment 1, which can be used to detect all of the serotypes, as well as geographic variants (different topotypes) of BTV, EHDV, AHSV, EEV and PHSV. Type-specific real-time RT-PCR assays that target the most variable genome segment 2 can be used to differentiate 25 serotypes of BTV or the seven serotypes of EHDV. These diagnostic assays were found to be very sensitive, reproducible and suitable for rapid screening of field samples. Results will be presented from studies to optimise these RT-PCR assays.

Evidence for transplacental and contact transmission of bluetongue virus in cattle

This paper presents evidence that a field strain of bluetongue virus serotype 8 (BTV-8) was transmitted transplacentally and that it was also spread by a direct contact route. Twenty pregnant heifers were imported from the Netherlands into Northern Ireland during the midge-free season. Tests before and after the animals were imported showed that eight of them had antibodies to bluetongue virus, but no viral RNA was detected in any of them by reverse transcriptase-PCR (RT-PCR). Two of the seropositive heifers gave birth to three calves that showed evidence of bluetongue virus infection (RT-PCR-positive), and one of the calves was viraemic. Two further viraemic animals (one newly calved Dutch heifer, and one milking cow originally from Scotland) were also found to have been infected with BTV-8 and evidence is presented that these two animals may have been infected by direct contact, possibly through the ingestion of placentas infected with BTV-8.

Regional seroprevalence of bluetongue virus in cattle in Illinois and western Indiana

To estimate seroprevalence of bluetongue virus (BTV) and the geographic distribution of seropositive cattle herds in Illinois and western Indiana. 10,585 serum samples obtained from cattle in 60 herds during 3 transmission seasons (2000 through 2002). In a longitudinal study, serum samples were tested for BTV antibodies by use of a competitive ELISA. Four geographic zones were created by use of mean minimum January temperature. A multivariable mixed-effects logistic regression model with a random effect for herd was used to estimate seropositive risk for zone, age of cattle, herd type, and transmission season. Overall, BTV antibodies were detected in 156 (1.5%) samples. Estimated seroprevalence in 2000, 2001, and 2002 was 1.49%, 0.97%, and 2.18%, respectively. Risk of being seropositive for BTV was associated with geographic zone and age. Seroprevalence increased progressively from northern to southern zones, with no evidence of BTV infection in the northernmost zone. In the southernmost zone, annual seroprevalence ranged from 8.65% to 11.00%. Adult cattle were 2.35 times as likely as juvenile cattle to be seropositive. Overall seroprevalence was lower than has been reported for Illinois cattle. Bluetongue virus antibodies were distributed heterogeneously in this region. Only in the southernmost zone was seroprevalence consistently > 2%. Regionalization of BTV risk based on state borders does not account for such variability. Serologic data could be combined with landscape, climate, and vector data to develop predictive models of BTV risk within transitional regions of the United States.

Development and evaluation of an IgM-capture ELISA for detection of recent infection with bluetongue viruses in cattle

An IgM-capture enzyme-linked immunosorbent assay (ELISA) was developed for the detection of recent infection of bluetongue virus (BTV) in cattle. The test is based on the use of biotinylated capture anti-bovine IgM antibodies bound to a streptavidin-coated ELISA plate. The captured IgM antibodies were detected by application of BTV VP7 antigen and a VP7 antigen-specific monoclonal antibody. The IgM-capture ELISA was compared with the competitive ELISA by testing serum samples from groups of calves infected experimentally with five USA and 19 South Africa serotypes of BTV. The IgM-capture ELISA was able to detect bovine anti-VP7 antibodies from all animals infected with the 24 BTV serotypes at 10 days post-infection, whereas the competitive ELISA was not. When the detectable IgM diminished after 40 days post-infection by the IgM-capture ELISA, the IgG anti-VP7 antibodies remained high. The IgM-capture ELISA is sensitive and can be applied for the detection of recent infection of BTV in cattle.

The role of cell-mediated immunity in the pathogenesis of bluetongue virus serotype 11 in the experimental infection of vaccine/sensitized calves

The cellular immune response of cattle to virulent and avirulent (inactivated) bluetongue virus (BTV) was studied. Each of three calves received three vaccinations (sensitizations) with binary ethyleneimine (BEI)-inactivated BTV, 3 weeks apart. The sensitized animals were challenged with BTV-11 strain UC8 3 weeks after the last vaccination. BTV-seropositive and BTV-seronegative calves were used as controls. The animals were bled weekly for virus isolation and for evidence of cell-mediated immunity (CMI) as determined by the lymphocyte stimulation test (LST). Peripheral blood mononuclear leukocytes (PBML) cultures were induced with purified BTV antigen; the phytomitogens phytohemagglutinin (PHA), Concanavalin A (ConA) and pokeweed (PKW) mitogen, and combinations of phytomitogens and BTV antigen. LST data were analysed by ANOVA and reported as counts per minute (CPM) and stimulation index (SI). Following BTV challenge exposure, significant SI to mitogens were found in PBML cultures for all animals. BTV antigen induced a weak CMI response. There was evidence of perturbations in lymphocyte response as characterised by a sharp decrease in lymphocyte response to mitogens following combined BTV-antigen and mitogen PBML induction. The SI diminished in PBML cultures after a 4 day incubation period, except for ConA. These results provide evidence that the cell-mediated immune response could be affected by BTV and that inhibitory mediators might play an important role in the pathogenesis of BTV in cattle.

Antibody to bluetongue virus in cattle in Ecuador.

Antibody to bluetongue virus in cattle in Ecuador.