Climate change: effects on culicoides--transmitted viruses and implications for the UK.

Changes in the distribution and abundance of insects are likely to be amongst the most important and immediate effects of climate change. We review here the risk that climate change poses to the UK's livestock industry via effects on Culicoides biting midges, the vectors of several arboviruses, including those that cause bluetongue (BT) and African horse sickness (AHS). The major old-world vector of BT and AHS viruses, C. imicola, occurs in southern Europe and will spread further north as global temperatures increase. It is unlikely, however, that in the foreseeable future it will reach and become established in the UK. As the distribution of C. imicola moves north, however, it may bring BT and AHS viruses into the range of other Culicoides species that are known to be competent vectors and which occur much further north. Once infected via this 'baton effect', these species may be able to spread the viruses over much of Europe, including the UK. Climate change may increase their vector competence further and will also increase the likelihood of viruses surviving from one year to the next. An additional risk is that the predicted increase in the frequency of short periods of hot temperatures may lead to the creation of novel vector species, by removing the barriers that in colder conditions make them refractory to viral infection. Copyright 2000 Harcourt Publishers Ltd.