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Bluetongue (BT) is one of the important viral diseases of domestic and wild ruminants, especially small ruminants such as sheep. Out of the 29 BTV serotypes prevalent in the world, at least 24 of the serotypes are reported in India, either by virus isolation or serology. To better understand the seroprevalence of BTV, we conducted a comprehensive study in the main reservoir hosts of BTV, i.e., cattle and buffaloes of different age groups in Andhra Pradesh and Telangana states of India where the disease is majorly prevalent. A total of 321 blood samples collected from cattle and buffaloes during 2017-2018 were tested for group-specific BTV seroprevalence by c-ELISA, followed by type specific seroprevalence (against BTV-1, 2, 4, 5, 9, 12, 16, and 24) by serum neutralization test. Of the 311 BTV seropositive samples, 112, 98, 102, 127, 2, 113, 160, and 5 samples neutralized BTV-1, 2, 4, 5, 9, 12, 16, and 24, respectively. Twenty-nine samples could not neutralize any of the tested BTV serotypes. Majority of the sera neutralized more than one serotype, up to a maximum of six serotypes. Major finding of the study is detection of BTV serotypes not included in the commercial pentavalent inactivated vaccine. Regular surveillance of circulating serotypes, especially in sentinel reservoir hosts throughout the country can help in designing better multivalent vaccines with suitable vaccine strains, for specific geographic regions.

Bluetongue (BT) is a Culicoides-borne disease caused by several serotypes of bluetongue virus (BTV). Similar to other insect-borne viral diseases, distribution of BT is limited to distribution of Culicoides species competent to transmit BTV. In the tropics, vector activity is almost year long, and hence, the disease is endemic, with the circulation of several serotypes of BTV, whereas in temperate areas, seasonal incursions of a limited number of serotypes of BTV from neighbouring tropical areas are observed. Although BTV is endemic in all the three major tropical regions (parts of Africa, America and Asia) of the world, the distribution of serotypes is not alike. Apart from serological diversity, geography-based diversity of BTV genome has been observed, and this is the basis for proposal of topotypes. However, evolution of these topotypes is not well understood. In this study, we report the isolation and characterization of several BTV-4 isolates from India. These isolates are distinct from BTV-4 isolates from other geographical regions. Analysis of available BTV seg-2 sequences indicated that the Australasian BTV-4 diverged from African viruses around 3,500 years ago, whereas the American viruses diverged relatively recently (1,684 CE). Unlike Australasia and America, BTV-4 strains of the Mediterranean area evolved through several independent incursions. We speculate that independent evolution of BTV in different geographical areas over long periods of time might have led to the diversity observed in the current virus population., (© 2017 Blackwell Verlag GmbH.)

Bluetongue is endemic in India and has been reported from most Indian states. Of late, the clinical disease is most frequently seen in the states of Andhra Pradesh, Telangana (erstwhile Andhra Pradesh state), Tamil Nadu and Karnataka. Our analysis of diagnostic samples from bluetongue outbreaks during 2010-2011 from the state of Karnataka identified bluetongue virus (BTV) serotype 5 (BTV-5) for the first time in India. One of the diagnostic samples (CH1) and subsequent virus isolate (IND2010/02) contained both BTV-2 and BTV-5. Segment 2 (seg-2) sequence data (400 bp: nucleotides 2538-2921) for IND2010/02-BTV5, showed 94.3% nucleotide identity to BTV-5 from South Africa (Accession no. AJ585126), confirming the virus serotype and also indicating that Seg-2 was derived from a Western topotype, which is in contrast to serotype 2, that belongs to an Eastern topotype. BTV-5 has been recently reported from Africa, China, French islands and the Americas. Although the exact source of the Indian BTV-5 isolate is still to be confirmed, recent identification of additional exotic serotypes in India is of real concern and might add to the severity of the disease seen in these outbreaks., (© 2016 Blackwell Verlag GmbH.)

Tamil Nadu is located in the South-Eastern part of Indian peninsula, between 8.087° and 13.09°N and 76.50° and 80.27°E. Bluetongue (BT) was first reported in this region in sheep during 1982 with regular occurrence thereafter. In 1989-1990, 1997-1998 and 2005-2006, there was wide spread occurrence of BT resulting in huge mortality of sheep. The present study had the goal of isolating the BTV from outbreaks in sheep occurred in Tamil Naadu between 2003-2011 and comparing the VP2 gene sequences of the BTV isolates involved in such outbreaks. Serotypes 1, 2, 16, and 23 of the Bluetongue virus (BTV) have been isolated from sheep during BT outbreaks. BTV-16 has also been isolated in goats and cattle in the region; BTV-2 isolated in Tamil Nadu has homology with BTV-2 isolated in Africa; whereas the BTV-23 isolated in this area has homology with BTV-23 from South East Asia, indicating that both Eastern and Western topotypes of BTV are circulating in ruminant population in Tamil Nadu.

Bluetongue (BT) is an insectborne endemic disease in India. Although infections are observed in domestic and wild ruminants, the clinical disease and mortality are observed only in sheep, especially in the southern states of the country. The difference in disease patterns in different parts of the country could be due to varied climatic conditions, sheep population density and susceptibility of the sheep breeds to BT. Over the five decades after the first report of BT in 1964, most of the known serotypes of bluetongue virus (BTV) have been reported from India either by virus isolation or by detection of serotype-specific antibodies. There have been no structured longitudinal studies to identify the circulating serotypes throughout the country. At least ten serotypes were isolated between 1967 and 2000 (BTV-1-4, 6, 9, 16-18, 23). Since 2001, the All-India Network Programme on Bluetongue and other laboratories have isolated eight different serotypes (BTV-1-3, 9, 10, 12, 16, 21). Genetic analysis of these viruses has revealed that some of them vary substantially from reference viruses, and some show high sequence identity with modified live virus vaccines used in different parts of the world. These observations have highlighted the need to develop diagnostic capabilities, especially as BT outbreaks are still declared based on clinical signs. Although virus isolation and serotyping are the gold standards, rapid methods based on the detection of viral nucleic acid may be more suitable for India. The epidemiological investigations also have implications for vaccine design. Although only a handful serotypes may be involved in causing outbreaks every year, the combination of serotypes may change from year to year. For effective control of BT in India, it may be pertinent to introduce sentinel and vector traps systems for identification of the circulating serotypes and to evaluate herd immunity against different serotypes, so that relevant strains can be included in vaccine formulations., (© 2014 Blackwell Verlag GmbH.)

Bluetongue virus (BTV) causes disease mainly in sheep, but can be transmitted via other domestic and wild ruminants, resulting in pecuniary burden and trade restrictions. Segmented genome with the possibility of reassortment, existence of 26 serotypes, geographical restriction in the distribution of many of the serotypes, use of live attenuated vaccines and the lack of complete sequences of viruses isolated from several parts of the globe have complicated our understanding of the origin, movement and distribution of BTV. Recent efforts in genome sequencing of several strains have helped in better comprehending BTV epidemiology. In an effort to contribute to the genetic epidemiology of BTV in India, we report the isolation and complete genome sequencing of a BTV serotype 12 virus (designated NMO1). This is the first BTV-12 isolated from India and the second BTV-12 to be sequenced worldwide. The analysis of sequences of this virus suggests that NMO1 derived its segments from viruses belonging to western topotype viruses, as well as those from South-East Asia and India. The results have implications for understanding the origin, emergence/re-emergence and movement of BTV as well as for the development of vaccines and diagnostics based on robust epidemiological data., (© 2013 Blackwell Verlag GmbH.)

Bluetongue virus serotype 21 (BTV-21) was originally isolated from Australia, but has now been reported from India, Indonesia, China and Japan. We report the isolation, and sequencing of BTV-21 from India. The complete ORF sequence of VP2 gene of this isolate showed that it is closely related to recent BTV-21 isolates from Japan (93-94% identity), and distantly related to BTV-21 reference strain (86% identity). Our results, along with the available sequences of Japanese isolates, suggest that the currently circulating BTV-21 strains from India and Japan are divergent from the original strain(s) from Australia and shed light on designing molecular diagnostics for the detection of BTV.

Recent incursions of bluetongue virus (BTV) into previously naive geographical areas have emphasised the need to better understand virus movement and epidemiology. Several bluetongue virus (BTV) serotypes are known to exist in India, and some serotype viruses have been isolated. However, the complete genome of not a single isolate is available to date. We report the complete genome sequence of one, and partial sequences of three other Indian isolates of BTV-9. Evolutionary relationships with segment-2 and -6 sequences of BTV isolates around the world, deduced using four different phylogenetic analyses and a similarity programme, show that BTV-9 (Eastern), BTV-9 (Western), and BTV-5 form a triad of equidistant, genetically distinct groups of viruses. The Indian BTV-9 isolates were closely related to Mediterranean and European BTV-9 isolates (Eastern topotype) based on segment-2 and -6 sequences. By contrast, segment-5 analyses clustered the Indian BTV-9 isolates with South African BTV-3 reference strain (98% identity), which belongs to one of the Western types. These results have implications on BTV origin and movement, genotyping, serotyping, and vaccine design.

Bluetongue, a transboundary disease, is endemic in several tropical countries and is caused by bluetongue virus (BTV). The origin and movement of BTV can be predicted by comparing nucleotide sequences of its segmented RNA genome. Such analyses have been useful in evaluating the source of the virus responsible for recent incursion of BTV into previously unreported areas. Besides several serotypes, genetically related BTV strains circulate in each endemic area, but such clusters of strains have been reported to be distinct from one geographical region to another. We obtained partial or complete sequences of the open reading frames encoded by VP2, VP6, VP7, NS1 and NS2 genes of a BTV-10 isolate of India and compared them with other BTV-10 sequences available in public database. Sequences of all the five genes showed >99% identity to BTV-10 prototype, vaccine strain and vaccine-like virus isolates from the USA. Our results suggest that Indian BTV-10 virus analysed in this study possibly originated from the United States., (© 2011 Blackwell Verlag GmbH.)

India is enzootic for bluetongue (BT), a predominant disease of small ruminants. The most important task in the control of disease is rapid and sensitive detection of virus. The present study was undertaken to standardize immunofluorescence (IFT) and immunoperoxidase tests (IPT) employing BTV serogroup specific VP7 monoclonal antibodies (MAbs), polyclonal homologous and polyclonal heterologous antisera against specific serotypes of BTV for detection of BTV antigen. Serial tenfold dilutions of BTV-9 were tested for limit of detection (LoD) of IFT, IPT and molecular assays by using MAbs against VP7, homologous anti-BTV-9 serum, and heterologous anti-BTV-16 serum. LoD of IFT was found to be 101 TCID50/mL using MAbs against VP7, anti BTV-9 serum, and anti BTV-16 serum. LoD of IPT was found to be 101 TCID50/mL, 102 TCID50/mL, and 102 TCID50/mL using MAbs against VP7, anti BTV-9 serum and anti BTV-16 serum, respectively. LoD of RT-PCR was 101 TCID50/mL and that of real time PCR was 100 TCID50/mL. This standardized assay was then applied for BTV detection in BTV suspected field samples collected from BT outbreaks followed by confirmation with virus isolation and NS3 group specific PCR. The current study shows that IFT and IPT are specific tests for group specific BTV identification. For IFT, monoclonal and polyclonal (homologous and heterologous) source of antibodies had similar sensitivity in the ability of BTV detection; whereas the most sensitive mode of detection by IPT was with MAbs. [ABSTRACT FROM AUTHOR]

Bluetongue (BT) disease caused by BT virus (BTV) is an acute haemorrhagic disease of domesticated and wild ruminants. 29 BTV serotypes have been identified so far throughout the world with 24 circulating in India conferring no cross protective immunity. Hence, the objective of the current study was to investigate the possibility of developing a recombinant subunit protein based vaccine for BT that is cross protective to all the known serotypes of BTV. VP2 is a major serotype determining protein and vaccination with VP2 was known to induce neutralizing antibody response. Since BTV circulates as 29 immunologically distinct serotypes, the current study aimed to identify conserved region of VP2. The amino acid sequence alignment showed that although VP2 was very variable among serotypes, several regions were relatively more conserved between serotypes; most conserved region (cVP2) of which was evident from 338-383aa. Moreover, selection pressure analysis revealed that all the codons in cVP2 region were under strong negative selection (dN/dS=0.16) suggesting strong structural and functional constraints on cVP2. In addition, two MHCI, MHCII each, and three B cell epitopes were predicted based on the physicochemical properties of the amino acids in cVP2 region. This suggests strong immunogenicity of cVP2 making it a suitable vaccine candidate. Taken together, cVP2 appears to be a promising target for a broad-spectrum subunit vaccine moiety for BT that can confer protection against the available serotypes of BTV. Since all the structural proteins of BTV will not be used in such subunit vaccines, observations from current study can also be extended to develop a marker vaccine for DIVA against BT. [ABSTRACT FROM AUTHOR]

Bluetongue (BT) is a viral disease of ruminants and is caused by different serotypes of bluetongue virus (BTV), which is transmitted by several species of Culicoides midges. The disease is endemic in tropical areas, and incursions have been observed in some of the temperate areas. Twenty-seven recognized serotypes of BTV have been reported so far. Some serotype viruses have been shown to circulate in certain geographical areas. BTV-24 has been reported from Africa, the Mediterranean and the Americas, whereas it is exotic to Australasia. Here, we report isolation of BTV-24 from India and show that it has high sequence homology in genome segment 2 with other Western isolates of BTV-24. Entry of this serotype into Australasian region is a cause of concern. [ABSTRACT FROM AUTHOR]

The article discusses the study on the efficiency of montanide and aluminum hydroxide gel (Al-gel) adjuvants in the development of humoral and cellular immunity for a bluetongue (BT) inactivated vaccine. The study found that montanide adjuvanted vaccine was slightly more potent when compared with Algel adjuvanted vaccine in eliciting neutralizing antibodies, and no significant difference in cell mediated immune (CMI) response for both.

Background and Aim: Bluetongue (BT) is a major disease of sheep and goats and is endemic to India. It is known to cause significant economic losses to the sheep industry. The current study aimed to determine the type-specific seroprevalence of BT in sheep population of India during 2018-2019. Materials and Methods: Blood samples (n=405) were collected from 6 months to 1 year old sheep from six districts (Nalgonda, Karimnagar, Khammam, Mahabubnagar, Warangal, and Ranga Reddy) of Telangana state, India. Group- and type-specific seroprevalence (against BT virus [BTV] serotypes BTV-1, 2, 4, 5, 9, 10, 12, 16, 21, 23, and 24) was studied by competitive enzyme-linked immunosorbent assay and serum neutralization test, respectively. Results: Results showed an overall seroprevalence of 14.81% (n=60) with the highest seroprevalence of 50% in Khammam district. Seroprevalence of BTV-1, 2, 4, 5, 9, 10, 12, 16, 21, 23, and 24 was noted as 16.66%, 11.66%, 31.66%, 11.66%, 05%, 6.66%, 16.66%, 8.33%, 13.33%, 6.66%, and 16.66%, respectively. The majority of the sera neutralized more than 1 serotype, indicating superinfection or circulation of multiple serotypes in the sampled flocks. This mixed seroprevalence was observed in 43.33% of the sera with number of BTV serotype-specific antibodies ranging from two to eight in individual animals. Conclusion: Regular monitoring of circulating serotypes, especially in young herds, elucidates pattern of dominating serotypes in a particular area during a season. This knowledge can be applied to design appropriate vaccination strategies by including particular serotypes of virus as part of a multivalent vaccine for a particular period, in a particular area. [ABSTRACT FROM AUTHOR]

Aim: The current study was designed to understand the infection kinetics and antibody responses of major circulating serotypes of bluetongue virus (BTV) in India, i.e., BTV-4 and BTV-16 through experimental infection and superinfection of Deccani sheep, a popular breed of sheep found in the southern states of India. Materials and Methods: Experimental infection with 106 TCID50/ml BTV-4 was followed by superinfection with BTV-16 and vice versa. Along with observing for clinical signs and immunological responses in the experimentally infected sheep, the effect of infection of one specific serotype on the outcome of superinfection with a different serotype was also studied. Results: Certain interesting findings have been made in the course of experimental infection, such as prominent signs of infection in BTV-4 infection, mild or no clinical signs in BTV-16-infected and superinfected animals, and non-seroconversion of one of the BTV-16-superinfected animals. In addition, BTV was isolated from infected sheep in all the experimental conditions except BTV-16 superinfection. Furthermore, it was observed that immune response in the form of type-specific antibodies was slower with BTV-16 superinfection. Conclusion: Superinfection of a sheep with more than one serotype of BTV is a common phenomenon in BT endemic countries like India. Such situation was replicated in an experimental infection in the current study, and the findings to our knowledge are first of a kind and are likely to aid in unfolding the newer aspects of BTV pathogenesis and virulence. [ABSTRACT FROM AUTHOR]