Culicoides

Last update: 15 March 2011

Culicoides-borne diseases (CBD) have been a central feature of veterinary epidemiology over the past decade, the accelerated occurrence of waves of CBD epizootics in the Mediterranean Basin and Europe having major economic consequences. Bluetongue (BTV) in domestic and wild ruminants has been the most important so far, but other CBD are lurking on Europe’s borders, including epizootic haemorrhagic disease in ruminants and African horse sickness and horse encephalosis.

For years the northward spread of these diseases, from sub-Saharan Africa and the Middle East to Europe has been associated with the extension of the distribution of their main Afro-asiatic vector, Culicoides imicola. The potential introduction of CBD into new areas by wind-borne spread of infected midges and livestock movements has recently been accommodated into risk analyses, and EDENext will be integrating information on these mechanisms with potential routes of entry which are currently poorly described, such as trade in contaminated biological materials (including the use of vaccines), transport of infected Culicoides with livestock or other cargos and the import of exotic hosts.

The emergence of several BTV serotypes in Northern Europe from 2006 has confirmed that endemic Culicoides species are able to transmit BTV efficiently and that overwintering mechanisms are able to maintain the virus in animal hosts and/or infected vectors.

The risk of establishment of orbiviruses across different conditions (climate, landscape, hosts, vectors) in Europe is dependent on Culicoides vector competence and abundance, demography and habitat use. Susceptibility to orbiviruses is expected to vary within and between key vector species in Europe and to depend on climatic conditions and EDENext will develop standardised protocols for assaying vector competence and levels of infection.

It will also be examining the influence of temperature and humidity on demographic rates of adults of key European Culicoides species in the laboratory and use existing datasets to evaluate the climate, host and landscape drivers of geographical variation in their seasonal abundance, demography and phenology. Novel techniques such as grading the age of adults and drop-trap experiments to quantify the discrepancies between trap catches and the number of midges found biting hosts will improve the accuracy of these investigations. The resulting vector model framework will lead to improved predictions of the ‘vector-free period’ required to permit livestock movements in affected areas over winter that are currently based only on the temperature requirements for viral replication.

Last update: 15 March 2011

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