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Vector-borne viral diseases

The arrival of the ruminant disease bluetongue (BT) for the first time ever in the UK in 2007 dramatically demonstrated the reality of the threat that is posed to our livestock by arboviruses – viruses that are transmitted to mammalian hosts by arthropods e.g. midges and ticks. Biting midges transmit BT virus and related viruses of ruminants and horses that are endemic in most of Africa, and are already present in countries on the edges of Europe. The tick-borne virus of African swine fever (ASF) was also transported inter-continentally, also in 2007, from sub-Saharan Africa to Georgia, from where it spread devastatingly, including close to the border with the EU.

We study the interactions of the arthropods with both the viruses and the mammalian hosts and the involvement of climate. We use our research results to design and implement improved disease control strategies. The Vector-borne Viral Diseases (VVD) Programme includes the Non-Vesicular Disease Reference Laboratory, which provides diagnostic services and advice for Defra, the World Organisation for Animal Health (OIE) and the European Union.

Our scientific priorities are to understand:

  • Why certain arthropod-borne viruses emerge in Europe, and what factors determine changes in their distribution, persistence in the environment, and evolution
  • The features of the viruses that enable their interaction with both their arthropod and livestock hosts, affecting the range of arthropod and mammals that are affected, the virulence of the virus, and the nature of the disease caused
  • The role of the arthropod vectors in the distribution and intensity of arbovirus outbreaks
  • How the immune systems of livestock combat arboviral infections

Our research has additional impact arising from:

  • Its underpinning of the diagnosis service provided by our Non-Vesicular Disease Reference Laboratory
  • Emergency response capacity for the UK
  • Modelling of the diseases for prediction of emergence and spread within northern Europe
  • The Institute's role as a hub for collaboration with research and surveillance partners worldwide
  • Development of diagnostic tools for internal and worldwide use
  • Development of vaccines
  • Training of livestock industry professionals, diagnosticians and students

Unique resources:

  • Experts on the biology, transmission and control of arboviral diseases of livestock
  • New laboratories and large-animal experimentation facilities at very high bio-containment levels (SAPO 3 and 4) for research on viruses from overseas
  • Insectaries where we rear colonies of Culicoides midges and soft ticks, with scope to maintain other arthropod species
  • Cattle and inbred pigs of known genetic background (defined MHC Class I haplotypes)
  • Cloned cattle MHC genes that determine protective immune responses

The growth of some viruses in vectors, such as midges, mosquitoes and ticks, which then transmit the virus to mammals whilst taking a blood meal, hugely adds to the risk of these viruses spreading great distances in a very short time and, consequently, complicates our capacity to defend against them. Being able to do the latter requires expertise in diagnosis, entomology, epidemiology, genetics, immunology, mathematical modelling, molecular biology and virology; we have all that within the VVD Programme. Plus we also have essential meteorological input from our collaboration with the UK Met Office.

Our efforts, in partnership with many others, including farmers, veterinarians, vaccine producers, Defra and overseas authorities resulted in the early control of the 2007 bluetongue (BT) outbreak in the UK. In contrast, continental northern Europe, in which the virus arrived one year earlier, when no vaccine was available, had scores of thousands of cases in cattle, sheep and goats.

Our expertise extends to relatives of BT virus (all of which are orbiviruses), including epizootic haemorrhagic disease virus (EHDV), which also affects ruminants, and African horse sickness virus (AHSV) which would probably kill 90% of affected horses in the UK.

We also study two viruses that can be transmitted by, and survive for long times in, ticks. One of these is Nairobi sheep disease virus (NSDV, a bunyavirus) in Africa, closely related to (and providing an important model for) Crimea Congo haemorrhagic fever virus of humans. The other is African swine fever virus (ASFV, an asfivirus), which kills virtually 100% of affected pigs.

The Institute has the Non-Vesicular Disease Reference Laboratory on behalf of Defra, the World Organisation for Animal Health (OIE) and the European Union in respect of bluetongue, peste des petits ruminants, rinderpest, African swine fever, African horse sickness, sheep and goat pox, and lumpy skin disease.

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