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A wind density model to quantify the airborne spread of Culicoides species during north-western Europe bluetongue epidemic, 2006

Hendrickx G., Gilbert M., Staubach C., Elbers A.R.W., Mintiens K., Gerbier G., Ducheyne E.. 2008. Preventive Veterinary Medicine, 87 (1-2) : p. 162-181.

DOI: 10.1016/j.prevetmed.2008.06.009

Increased transport and trade as well as climate shifts play an important role in the introduction, establishment and spread of new pathogens. Arguably, the introduction of bluetongue virus (BTV) serotype 8 in Benelux, Germany and France in 2006 is such an example. After its establishment in receptive local vector and host populations the continued spread of such a disease in a suitable environment will mainly depend on movement of infected vectors and animals. In this paper we explore how wind models can contribute to explain the spread of BTV in a temperate eco-climatic setting. Based on previous work in Greece and Bulgaria filtered wind density maps were computed using data from the European Centre for Medium-Range Weather Forecasts (ECMWF). Six hourly forward wind trajectories were computed at pressure levels of 850 hPa for each infected farm as from the recorded onset of symptoms. The trajectories were filtered to remove wind events that do not contribute to possible spread of the vector. The suitable wind events were rastered and aggregated on a weekly basis to obtain weekly wind density maps. Next to this, cumulated wind density maps were also calculated to assess the overall impact of wind dispersal of vectors. A strong positive correlation was established between wind density data and the horizontal asymmetrical spread pattern of the 2006 BTV8 epidemic. It was shown that short (<5 km), medium (5-31 km) and long (>31 km) distance spread had a different impact on disease spread. Computed wind densities were linked to the medium/long-distance spread whilst short range spread was mainly driven by active Culicoides flight. Whilst previous work in the Mediterranean basin showed that wind driven spread of Culicoides over sea occurred over distances of up to 700 km, this phenomenon was not observed over land. Long-distance spread over land followed a hopping pattern, i.e. with intermediary stops and establishment of local virus circulation clusters at distanc

Mots-clés : culicoides; virus bluetongue; vecteur de maladie; facteur climatique; vent; migration animale; transmission des maladies; modèle de simulation; épidémiologie; europe; Émergence

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