Bluetongue Virus Antibodies Research Articles

Current Status of Bluetongue Disease, Its Vector and Pathogenesis in India

Bluetongue (BT) is a Culicoides (Diptera: Ceratopogonidae) borne, infectious, noncontagious, economically important viral disease of sheep and other domestic and wild ruminants. Humans are not affected although some species of Culicoides feed on human blood also. The disease has the potential to spread rapidly, which can cause serious socio-economic consequences in view of mandatory trade barrier on the movement of animals, their germplasm, embryo and other animal products from BT endemic to BT free countries. The first outbreak of BT in sheep and goats in the country was recorded in 1964 in Maharashtra State. Since then, several outbreaks of BT have been reported in sheep in almost all states of the India. A serological survey has indicated the presence of bluetongue virus (BTV) antibodies in the Indian cattle, buffalos, goats, camels and some wild ruminants. However, clinical BT has not been observed in cattle or buffalo to date, whereas in goats, there are sporadic reports of occurrence of clinical BT either alone or as co-infection with peste des pestis ruminants. Although BTV has been isolated from Culicoides midges, the particular species responsible for transmission has not yet been identified. BTV is the prototypic member of the genus Orvivirus, family Reoviridae. BTV a non enveloped icosahedral virus consists of a ten segmented, double stranded RNA genome encapsidated in a double layered protein coat. Immunization programme is in progress in India and multivalent inactivated adjuvant vaccine containing BTV serotypes 1, 2, 10, 16 and 23 has been developed. Discovery of VLPs and CLPs has opened a new era of vaccination. The vector of BT is the Dipteran spp. Culicoides. About 60 spp. of Culicoides are reported from India. The early ecological study indicates that Culicoidesmonocoli Maheshwari may be the potential vector. The studies on BT in India are in primary stages, which may open several of vital fields for future investigation.

Seasonal effects on the prevalence of bluetongue in small ruminants in west Azarbaijan, Iran.

BACK GROUND: Bluetongue virus (BTV) is recognized to infect ruminants all around the world, and its prevalence mainly depends on the BTV situation, vectors distribution, weather patterns and susceptibility of the host. Objectives: The purpose of this study was to draw a correlation between the prevalence of BTV antibodies and climate changes in Iranian Azerbaijan Province. METHODS: Sera samples were collected from sheep, in a period of a year between 2008- 2009. The seroprevalance of Bluetongue antibodies were evaluated using an Enzyme-linked Immunosorbent Assay, considering monthly weather changes in the Province, recorded by the Iran Meteorological Organization. RESULTS: The infection rate was found to be 55.9% and there was a peak BTV prevalence of at 81% (p

The first survey for antibody against Bluetongue virus in sheep flocks in Southeast of Iran

ObjectiveBluetongue virus is an arthropod-borne Orbivirus in the family Reoviridae which infects both domestic and wild ruminants. Bluetongue disease is a “List A” disease of the Office of International Epizootics. To the best of our knowledge, no report has been published on bluetongue disease of sheep flocks of Southeast of Iran. The objective of this study was to describe the seroprevalence rates of BTV in sheep flocks in southeast of Iran. MethodsThe blood samples were collected randomly from herds of Southeast of Iran. A total of 188 sera samples (94 male, 94 female) collected between 2009 and 2010, were available. Antibodies to BTV in sera were detected by using a commercial competitive ELISA (Institute Pourquier, Montpellier, France) according to manufacturer's instructions. ResultsThe seroprevalence rates were 6.57 % for sheep herds. Within a herd, prevalence of BTV seropositive animals ranged from 0% to 42.85%. 33.3% sheep flocks were positive to BTV antibodies. Sex didn't affect the rate of seropositivity, but the rate of seropositivity was significantly changed in different age groups. ConclusionThis study describes the seroprevalence rates of Bluetongue virus (BTV) in sheep flocks in southeast of Iran for the first time.

Seroprevalence of bluetongue virus antibodies in sheep in Kurdistan province in west of Iran

This study was conducted to determine the seroprevalence of bluetongue virus antibodies in sheep in Kurdistan province in west of Iran during 2011-2012. According to results, the seropositive rates of sheep in Kurdistan were 45.9%. The results showed that in area there is widespread presence of the bluetongue virus antibodies in the sheep population as 123 sheep’s out of 268 were affected.

High seroprevalence of bluetongue virus antibodies in Sheep, Goats, Cattle and Camel in different districts of Saudi Arabia

Aim: To estimate the prevalence and distribution of serum antibodies to BTV in different domesticated animals in different localities of Saudi Arabia. Materials and Methods: A total of 4845 field sera collected from different animal species within 10 districts in the Kingdom of Saudi Arabia were screened for the presence of group-specific BTV antibodies by competitive ELISA (c ELISA). Results: The overall BTV antibody prevalence was 54.1%, 53.3%, 44.8% and 25.7% in sheep, goat, cattle and camel respectively (at 95% confidence level). The Jizan and Eastern Province districts were the regions with the highest prevalence resulting 65.8% of sheep, 68.2% of goats, 49.3% of cattle, 44% of camel in Jizan and 65.8% of sheep, 62.5% of goats, 53.4% of cattle, 28.5% of camel in Eastern Province positive to c-ELISA. The second highest rate was in Najran district where the seropositivity for Bluetongue was found to be 60% of sheep, 57.9% of goats, 47.2% of cattle and 29.3% of camel. Our results recorded positive animals in all examined districts which indicate serological evidence of exposure to infection was widely distributed all over the country. Conclusions: These results demonstrate the high occurrence of the BTV that emphasize the necessity to a well-defined control strategy for preventing and controlling the BTV in Saudi Arabia.

Evaluation of commercial ELISA kits for the detection of antibodies against bluetongue virus

The aim of this study was to estimate the diagnostic value of different commercially available ELISA kits for the detection of bluetongue virus (BTV) antibodies in infected and vaccinated animals. The relative specificity of ELISA kits was evaluated using a panel of sera originating from healthy cattle, never vaccinated nor exposed to BTV. All ELISA kits applied had a high relative specificity (99.3 - 100%). The relative sensitivity of ELISA kits assessed using a panel of sera collected from BTV infected cattle was also high and similar for all the kits (97.3 - 100%). However, the relative sensitivity evaluated on the basis of testing vaccinated animals was different: the highest sensitivity was found for Ingenasa, PrioCHECK and ID VET ELISAs (96.5 - 98.3%). Slightly lower sensitivity was calculated for Pourquier and LSI kits (82.8% and 85.4%, respectively) and much lower sensitivity was found for VMRD ELISA kit (69.5%). The repeatability of BTV ELISA kits was expressed as a coefficient of variation (CV) of results of sera tested 5 times in the same day and in different days by the period of 2 months, by the same person, in the same conditions, and by using the same equipment. The CVs of sera tested in all ELISA kits ranged from 6.1 to 9.8% and were below 10% threshold adopted as a maximum for the acceptable repeatability of the method. In conclusion, it can be stated that the applied ELISA kits can be a valuable diagnostic tool for the serological monitoring studies in the BTV contaminated premises. All the methods are very specific and sensitive when testing BTV infected animals. Nevertheless, the Ingenasa and PrioCHECK can be the most useful in sero-surveillance of livestock following vaccination.

Evaluation of the efficacy of commercial vaccines against bluetongue virus serotypes 1 and 8 in experimentally infected red deer ( Cervus elaphus)

Red deer ( Cervus elaphus) is a widespread and abundant species susceptible to bluetongue virus (BTV) infection. Inclusion of red deer vaccination among BTV control measures should be considered. Four out of twelve BTV antibody negative deer were vaccinated against serotype 1 (BTV-1), and four against serotype 8 (BTV-8). The remaining four deer acted as unvaccinated controls. Forty-two days after vaccination (dpv), all deer were inoculated with a low cell passage of the corresponding BTV strains. Serological and virological responses were analyzed from vaccination until 28 days after inoculation (dpi). The vaccinated deer reached statistically significant ( P < 0.05) higher specific antibody levels than the non vaccinated deer from 34 (BTV-8) and 42 (BTV-1) dpv, maintaining stable neutralizing antibodies until 28 dpi. The non vaccinated deer remained seronegative until challenge, showing neutralizing antibodies from 7 dpi. BTV RNA was detected in the blood of the non vaccinated deer from 2 to 28 dpi, whereas no BTV RNA was found in the vaccinated deer. BTV was isolated from the blood of non vaccinated deer from 7 to 28 dpi (BTV-1) and from 9 to 11 dpi (BTV-8). BTV RNA could be identified by RT-PCR at 28 dpi in spleen and lymph nodes, but BTV could not be isolated from these samples. BT-compatible clinical signs were inapparent and no gross lesions were found at necropsy. The results obtained in the present study confirm that monovalent BTV-1 and BTV-8 vaccines are safe and effective to prevent BTV infection in red deer. This finding indicates that vaccination programs on farmed or translocated red deer could be a useful tool to control BTV.

Development of field-deployable instrumentation based on “antigen–antibody” reactions for detection of hemorrhagic disease in ruminants

Development of field-deployable methodology utilizing antigen–antibody reactions and the surface plasmon resonance (SPR) effect to provide a rapid diagnostic test for recognition of the blue tongue virus (BTV) and epizootic hemorrhage disease virus (EHDV) in wild and domestic ruminants is reported. A Spreeta chip, which utilizes microelectronic technology to implement the SPR effect, is shown to possess sufficient sensitivity and operating speed to detect either BTV and EHVD antigens or antibodies in real time. The biosensor consists of an outer active surface layer comprised of either an antibody or antigen immobilized by covalent bonds through several other organic layers including a self assembled monolayer to a gold surface. Parallel experiments were run on the biosensor surface using either a home-built high resolution SPR instrument or a low resolution solid state Spreeta SPR chip. Both instruments were capable of monitoring the antigen–antibody reaction used to selectively detect the presence of BTV and EHDV viral pathogens. Results for the antibody and antigen reactive layers with antigen or antibody solutions as well as the modeling of these layers are discussed. The characteristics of these biosensors – specificity and time of reaction – were assessed. The antibody surface biosensors exhibited a high degree of specificity, even when using low resolution instrumentation. The time of analysis was under 20min, which was the arbitrary exposure time.

Limitations of sandwich ELISAs for bluetongue virus antibody detection

COMPETITIVE ELISAs for the detection of antibodies to bluetongue virus (BTV) are well established and widely available (World Organisation for Animal Health [OIE] 2009). Recently, sandwich (double antigen) ELISAs have...

Orbiviruses in Rusa Deer, Mauritius, 2007

Orbiviruses in Rusa Deer, Mauritius, 2007

Occurrence of Dual Infection of Peste-Des-Petits-Ruminants and Goatpox in Indigenous Goats of Central India

Peste-des-petits-ruminants (PPR), bluetongue (BT) and goatpox (GP) have been well recognized as causes of significant economic losses in the small ruminant population of Asia and Africa. We describe here the occurrence of these three in an outbreak noticed in non-descript goats from a subtropical region of central India. An investigation was carried out to confirm the aetiology of the heavy mortality in goats (74.6%, 112/150), with testing of samples from 12 surviving animals exhibiting mixed clinical signs indicative of PPR, BT and GP. Sandwich ELISA was used to detect PPR virus antigen and competition ELISA to detect PPR virus and BT virus antibodies. GP was confirmed on the basis of nodular lesions and an immunodiffusion assay. Eight of the 12 affected animals (66.7%) were positive for PPR virus and BT virus antibodies, and two goats (16.7%, 2/12) exhibiting clinical lesions of pox were also found positive for PPR virus/antibodies and BT virus antibodies, respectively. Although BT virus could not be identified in any sample, detection of BT virus antibodies indicated previous or possibly concurrent infection with BT virus in these goats. The N-gene-based RT-PCR was used to confirm the PPR infection in these goats, and one of the amplicons was sequenced. The sequence and phylogenetic analysis revealed close proximity to PPR virus isolates from Tibet and China, with sequence homology of up to 96.9%. The sequence homology was relatively low with the majority of other Indian isolates (72.7-93.5%). The detection of this new PPR virus sequence indicates the circulation of cross-border strains in this region of India. It is presumed that the heavy mortality observed in goats is possibly attributable to the occurrence of mixed infection of PPR and GP, or PPR, BT and GP.

An outbreak of bluetongue virus serotype 9 in Southern Croatia

The aim of this study was to provide a description of the first epidemic of bluetongue and the first survey on midges of the genusCulicoidesin Croatia. Clinical signs were firstly observed on November 2001 in sheep in Konavle, Dubrovnik – Neretva County. During this epizootic the overall sheep morbidity and mortality were 5.2% (95% confidence interval (c.i.), 4.1-6.6%) and 2.29% (95% c.i., 1.6-3.3%), respectively. After the outbreak, 3,318 serum samples of ruminants from 53 villages of the Dubrovnik – Neretva County were examined for bluetongue virus (BTV) antibodies by competitive enzyme-linked immunosorbent assay (cELISA). In forty nine (92.45%, 95% c.i., 82.11-96.92%) of the 53 villages, animals with antibodies against bluetongue virus were found. In particular, a total of 178 cattle (49.86%, 95% c.i., 44.7-55.0%), 174 sheep (13.72%, 95% c.i., 11.9-15.7%) and 270 goats (15.95%, 95% c.i., 14.3-17.8%) were seropositive. Antibodies to bluetongue virus serotype 9 were detected in 212 positive sera by serum neutralization test. The percentage of positive animals decreased (P&gt; 0.05) from the east to the west suggesting a possible east westward spreading of BTV infection. Fourteen light-trap midge collections from seven different sites were examined. Of the 4872Culicoidesspp. collected, 4,492 (92%, 95% c.i., 91.4-92.9%) of them belonged to the species ofObsoletus complex. This study showed for the first time that a pathogenic strain of BTV-9, probably from Montenegro, entered Croatia causing disease and death in local sheep and thatC. obsoletusandC. scoticuswere likely the major vectors of infection.

A Rapid Assay for Detecting Antibody against Bluetongue Virus with a Latex Agglutination Test Using Recombinant VP7 Antigen

A latex agglutination test (LAT) for detecting antibody against Bluetongue virus (BTV) in ruminants was developed using latex beads coupled with recombinant VP7 protein. Compared with competitive enzyme-linked immunosorbent assay (ELISA), the specificity and sensitivity of the LAT were 99.0% and 93.0%, respectively. There was excellent agreement between the results obtained by competitive ELISA and the LAT (kappa = 0.930). Because it is rapid and easy to use, the LAT could be used for BTV antibody detection, especially for screening many serum samples.

Emergence of bluetongue virus serotype 6 in Europe—German field data and experimental infection of cattle

In late 2008, bluetongue virus (BTV) serotype 6 (BTV-6), which had never occurred in Europe before, was first detected in the Netherlands and Germany. While the origin of the virus remains unknown, the prevalence of infections in cattle was investigated in a virological ( N = 28,658) and serological ( N = 2075) field survey in Lower Saxony, where 45 cases confined to the district Grafschaft Bentheim were found. Blood from affected animals was used for the experimental infection of three cattle with different BTV antibody status, leading to sustained viraemia in one animal naïve for BTV. Of two animals that had detectable antibodies against BTV serotype 8, one became transiently infected and seroconverted for BTV-6 while the other did not react. In conclusion, while only a very limited spread of BTV-6 could be observed in the field, experimental infection of cattle did not show substantial differences of the course of infection in comparison to other BTV serotypes.

Programme national bulgare de surveillance du virus de la fièvre catarrhale : études de terrain et évaluation du risque en 2009

Bluetongue is a non-contagious, arthropod-borne viral disease of both domestic and wild ruminants. Bluetongue virus (BTV) is endemic in some areas where cattle and wild ruminants serve as reservoirs for the virus. Some authors suggest that a fundamental change in the European ecosystem since 1998, mostly linked to climate change, may have influenced the introduction and sur­vival of BTV in Europe. Genetic analyses of bluetongue viruses isolated in Europe during this period showed that six virus types (1, 2, 4, 8, 9 and 16) have entered the region since that period. The aim of this presentation was to summarize the results of the National BTV Surveillance Programme, field studies, and risk assessment of BTV entry into Bulgaria in 2009. As part of the Surveillance Programme of the disease in 2009, seroprevalence was performed in 19 sentinel BTV-seronegative animal herds, 7 of which were located in the western part of the country and the other 12 in the southern part, about 10 to 20 kil­ometres from the border. Each sentinel herd consisted of 10 large ear-tagged ruminants. The sentinel animals were tested every 30 days for the presence of BTV antibodies. Competitive enzyme-linked immunosorbent assays (cELISAs) were used to determine the antibodies against the common group antigen. Fourteen Onderstepoort black light traps were set up for Culicoides surveil­lance and monitoring in southern and western border districts of the country after April 1, 2009. Catches of Culicoides were sorted by traditional identification keys. The risk of BTV invasion was assessed according to the World Organisation for Animal Health standards. The hazard identification, possibility of BT outbreaks, and assessment of the epidemiological situation in neighbour­ing countries were made based on other authors’ reports on the density of small and large ruminants, and economical and trade relations between countries. In addition, the BTV situation on a Greek Aegean Sea Island was closely monitored in 2008-09. During the 2009 serum surveillance period, 3340 serum sam­ples from different species of ruminants were investigated, all with negative results for BTV antibodies; C. imicola was never detected in more than 12 years of Culicoides surveillance in Bulgaria. Analysis of 274 midges caught during 2009 showed that dominating Culicoides species were of the Obsoletus and Pulicaris complexes, well-known Palaearctic midges in Europe. The negative results from the Surveillance Programme supported the evidence of absence of active BTV circulation on the whole territory of Bulgaria during 2009. During the 2008-09 season, Greek Authorities reported several circulating BTV serotypes (1, 8, 16) on Lesvos Island. As the epidemiological situation on Greek islands in the Aegean Sea is complicated and not very clear, the risk of BTV entering Bulgaria ranges from high (in spring and summer) to moderate (in winter and autumn).

Bluetongue virus: European Community inter-laboratory comparison tests to evaluate ELISA and RT-PCR detection methods

European Community national reference laboratories participated in two inter-laboratory comparison tests in 2006 to evaluate the sensitivity and specificity of their ‘in-house’ ELISA and RT-PCR assays for the detection of bluetongue virus (BTV) antibodies and RNA. The first ring trial determined the ability of laboratories to detect antibodies to all 24 serotypes of BTV. The second ring trial, which included both antisera and EDTA blood samples from animals experimentally infected with the northern European strain of BTV-8, determined the ability of laboratories to detect BTV-8 antibodies and RNA, as well as the diagnostic sensitivity of the assays. A total of six C-ELISAs, six real-time RT-PCR and three conventional RT-PCR assays were used. All C-ELISAs were capable of detecting the BTV serotypes currently circulating in Europe (BTV-1, 2, 4, 8, 9 and 16), however some assays displayed inconsistencies in the detection of other serotypes, particularly BTV-19. All C-ELISAs detected BTV-8 antibodies in cattle and sheep by 21 dpi, while the majority of assays detected antibodies by 9 dpi in cattle and 8 dpi in sheep. All the RT-PCR assays were able to detect BTV-8, although the real-time assays were more sensitive compared to the conventional assays. The majority of real-time RT-PCR assays detected BTV RNA as early as 2 dpi in cattle and 3 dpi in sheep. These two ring trails provide evidence that national reference laboratories within the EC are capable of detecting BTV antibodies and RNA and provide specificity and sensitivity information on the detection methods currently available.

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.

No evidence of bluetongue virus in Switzerland

We report the results of the first survey for antibody against bluetongue virus (BTV) that was conducted in Switzerland in the year 2003. In a nationwide cross-sectional study with partial verification, 2437 cattle sera collected from 507 herds were analysed using competitive enzyme-linked immunosorbent assays (c-ELISA). To adjust for misclassification, 158 sera, including 86 that were recorded equivocal in Switzerland, were sent to the Office Internationale des Epizooties designated regional reference laboratory in the UK for confirmation. No BTV antibody was detected in any of these samples, confirming the absence of BTV from Switzerland in 2003. The specificity of the c-ELISA used in Switzerland for individual Swiss cattle was calculated to be 96.5%. The mean herd sensitivity achieved in our survey ranged from 78.9% to 98.8% depending on the with-in herd prevalence and test sensitivity used for the calculations. The cumulated confidence level achieved with the survey based on a minimal expected prevalence of 2%, was 99.99% and therefore it was concluded that there was no evidence of BTV circulation in Switzerland in 2003.

Prevalência de anticorpos contra o vírus da língua azul em bovinos e ovinos do Sudoeste e Sudeste do Rio Grande do Sul

It was studied bluetongue virus antibodies prevalence for sheep and cattle in Southwest and Southeast regions of Rio Grande do Sul State. A total of 2613 serum samples (1272 bovine and 1341 ovine) were tested by agar gel immunodiffusion. Eight bovine and two ovine samples were positive meaning a prevalence of 0.63% and 0.15%, respectively. These results show that most of animals in these regions are negative to bluetongue.

Seroprevalencia de anticuerpos contra el virus de la lengua azul en ovejas y cabras del estado de Kerala (India)

The results presented here record the first confirmation of bluetongue virus (BTV) antibody in sheep and goats in Kerala State. A total of 1,010 sera collected from the 14 districts within the state were screened for the presence of group-specific BTV antibodies by dot enzyme-linked immunosorbent assay (dot ELISA). Positive samples were obtained from 12 of the 14 districts. The overall BTV antibody prevalence was 5.1 +/- 1.9% (at 95% confidence level) although the prevalence levels were consistently higher in organised farms than in the field population. Comparative tests carried out using the dot ELISA and competitive ELISA (C ELISA) showed a good agreement for all the positive sera. The dot ELISA was simple to perform, economic and rapid, and is therefore ideally suited for routine screening for BTV antibody at the farm level.