Bluetongue (eBook)

Front Cover 1
Bluetongue 4
Copyright Page 5
Contents 6
Series Introduction 16
Preface 20
Acknowledgement 22
Chapter 1 Introduction 24
Background 24
Bluetongue, an emerging disease 25
Chapter 2 The history of bluetongue 30
Introduction 30
Geographical distribution 30
Host range 32
Aetiology 34
Transmission 36
Control 37
Chapter 3 Bluetongue virus, other orbiviruses and other reoviruses: Their relationships and taxonomy 46
Introduction 46
The genera of the family Reoviridae 51
The genus Orbivirus 52
Classification and differentiation of the Orbivirus species 53
The economically important orbiviruses 55
Emerging orbiviruses 58
Orbiviruses that can infect humans 59
Relationships with other reoviruses 60
Phylogenetic relationships of the orbivirus proteins 62
Phylogenetic relationships between the RNA- dependent RNA polymerase (Pol – RdRP) of the different orbiviruses 66
Phylogenetic relationships based on the sub-core shell T2 protein of bluetongue virus and other orbiviruses 67
Dating divergence times for bluetongue virus and epizootic haemorrhagic disease virus serotypes 69
Chapter 4 Bluetongue virus replication and assembly 76
Introduction 76
Arrangement of proteins in the virus outer capsid and their role in virus entry 77
Functional dissection of the enzymatic core proteins 80
Assembly of the viral core 84
Assembly of the viral outer capsid 89
Release of progeny virions from infected cells 90
Concluding remarks 94
Chapter 5 Bluetongue virus: cell biology 100
Introduction 100
Bluetongue virus entry into the cellular host 101
Viral structures and their functions 104
Interaction of bluetongue virus with the cytoskeleton 110
Involvement of the cellular translation machinery during bluetongue virus infection 111
Fate of bluetongue virus-infected cells and virus egress 112
Conclusions 117
Chapter 6 The structure of bluetongue virus core and proteins 124
Introduction 124
The bluetongue virion structure 125
Genome packaging 128
Enzyme functions and location 131
Substrate and product-binding sites 133
Binding of dsRNA to the bluetongue virus core surface 139
Bluetongue virus outer capsid proteins VP2 and VP5 143
Bluetongue virus non-structural proteins 144
Bluetongue virus particle structure and cell entry mechanisms 148
Chapter 7 Molecular epidemiology studies of bluetongue virus 158
Introduction 158
Variable and conserved genome segments 160
BTV incursions into Europe 169
Phylogenetic analyses of BTV core/non-structural proteins and identification of reassortants 178
Conclusions/Discussion 179
Chapter 8 Bluetongue in the Indian subcontinent 190
Introduction 190
Geographical distribution and seasonality 191
Clinical bluetongue in sheep 193
Serological prevalence of bluetongue in other animal species 199
Vectors 203
Bluetongue virus serotypes reported from Indian subcontinent 205
Diagnosis 207
Molecular epidemiology studies 209
Economic impact of bluetongue and control 210
Acknowledgments 212
Chapter 9 Current status of bluetongue virus in the Americas 220
Introduction 220
North America 221
Central America 228
South America 230
Virus–vector Interactions 233
Summary 235
Acknowledgments 235
Chapter 10 Bluetongue viruses in Australasia and East Asia 246
Introduction 246
Major studies of bluetongue virus in the region 247
Bluetongue disease in Australasia and East Asia 248
Bluetongue virus serotypes isolated in the region 249
The bluetongue virus genotypes in the region 252
The known and suspected Culicoides spp vectors 253
Conclusions 253
Chapter 11 Bluetongue in Europe and the Mediterranean Basin 258
Introduction 258
Bluetongue virus in the Mediterranean Basin, 1998–2005 259
Origins of the outbreaks 270
Vector species of Culicoides in Europe and the Mediterranean Basin 273
Bluetongue virus in Europe in 2006 and 2007 275
Mechanisms of overwintering 277
Summary 279
Chapter 12 Bluetongue virus in the mammalian host and the induced immune response 288
Introduction 288
Bluetongue virus infection of the ruminant host 289
Bluetongue virus replication in the ruminant host 290
Immune response 296
A potential bluetongue virus overwintering mechanism in the ruminant host 298
Conclusive remarks 300
Chapter 13 Clinical signs and pathology 308
Introduction 308
Clinical signs 309
The pathogenesis of bluetongue virus infection 311
Persistent bluetongue virus infection of cattle 313
Bluetongue in other animal species 314
Chapter 14 Bluetongue virus in the insect host 318
Introduction 318
Culicoides biting midges 319
Bluetongue virus 319
Vector species of Culicoides 320
Infection and replication of bluetongue virus in vector Culicoides 324
Bluetongue virus infection and susceptibility rates in vector species of Culicoides 326
Barriers to the infection, dissemination and transmission of arboviruses in insect vectors 328
A possible overwintering mechanism of bluetongue virus in vector Culicoides 330
Effects of temperature on arbovirus infection and transmission by insect vectors 332
Effect of temperature on bluetongue virus infection by vector Culicoides 332
Summary 335
Chapter 15 Rates of bluetongue virus transmission between Culicoides sonorensis and sheep 344
Introduction 344
Materials and methods 346
Results 350
Discussion 360
Acknowledgements 363
Chapter 16 Bluetongue virus and climate change 366
Introduction 366
The shifting pattern of European bluetongue epidemics 367
Evidence linking patterns in bluetongue to climate change 370
Extended distribution of the major Old World vector, C. imicola 373
Involvement of Palearctic vectors in bluetongue virus transmission in Europe 374
Why is the bluetongue virus–Culicoides episystem responsive to climate change? 378
A global view of climate change and bluetongue epidemiology 379
Acknowledgements 381
Chapter 17 Bluetongue virus diagnosis 388
Introduction 388
Clinical diagnosis 392
Virus isolation 393
Antibody/antigen-based assays 394
Molecular assays 400
Detection of BTV in Culicoides midges 407
Ring-trials and proficiency testing 409
Diagnostic samples 410
The future 411
Chapter 18 Bluetongue virus vaccines past and present 420
Introduction 420
Multiple BTV serotypes 424
Attenuated 'live' vaccines 425
Live vaccine 'platforms' 430
Inactivated BTV vaccines 431
Subunit vaccines 432
Differentiating infected from vaccinated animals 437
Adjuvants 440
Regulations and acceptability 442
Concluding remarks 443
Chapter 19 Bluetongue control strategies 452
Introduction 452
Risk factors 453
The BT virus 456
Methods of surveillance and monitoring 457
Modelling 461
Methods of control 461
Control strategies 464
International legislation 468
Chapter 20 Conclusions 476
Glossary 482
Index 488