Can we improve our preparedness against Culicoides -borne diseases using atmospheric dispersion model?
Amandine Bibard PhD Fellow in Epidemiology, Animal health Global Innovation
Europe faces regular introductions and re-introductions of Culicoides -borne diseases, most recently exemplified by the first introduction of the Epizootic Hemorrhagic Disease Virus (EHDV) in Europe in 2022 and the recent incursion of Bluetongue Virus (BTV) serotype 3 in the Netherlands. Both hemorrhagic fevers are recognized as global veterinary and public health concerns due to their economical and animal health impact.
Several routes of virus introduction have been imputed solely or in combination: import of live animals through legal or illegal trade, import of germplast (semen and/or embryos), movement of wild animals, airborne dispersion of vectors, import of immature stages of vectors or use of poorly attenuated modified live vaccines. While the long- distance wind dispersal of the disease virus vector, Culicoides spp., is recognized as a virus introduction pathway, it remains understudied in risk assessments. On the other hand, evidence of long-distance wind dispersion of Culicoides spp. has been shown for up to 700 km and 500 km over sea (Ducheyne et al. , 2011; D. Eagles et al. , 2012; Debbie Eagles et al. , 2014) and over land (García-Lastra et al. , 2012) respectively, under suitable conditions. Although considered important, the windborne dispersal of insects is extremely challenging to monitor since it is technically unfeasible to sample large volumes of air at the needed frequency, while predicting potential dispersal can only rely on modelling approaches based on atmospheric simulations. In recent years, the use of atmospheric dispersion models to mimic the atmospheric trajectories of flying vectors has been on the rise. Among these, HYSPLIT (Stein et al. , 2015), an open-source model originally developed
to simulate the trajectories of inert particles in the atmosphere, has been increasingly used to assess dispersal of fungus spores (Radici et al. , 2022), Culicoides spp. (Aguilar-Vega et al. , 2019; Debbie Eagles et al. , 2014; Jacquet et al. , 2016) and other flying insect (Hall et al. , 2022). Boehringer Ingelheim and academic partners developed a wind connectivity matrix, based on simulations from HYSPLIT model that has been adapted to Culicoides survival conditions (temperature, altitude, duration of flight), to evaluate when and how often two locations anywhere in Europe could be connected by the wind. A recent application of this methodology for EHDV- 8 in France showed that we predicted with good sensitivity the newly EHDV-infected areas in the south-west of France over a period of 5 weeks after its first introduction in the country. The predicted zone in France (excluding the source locations) captured 99.9% of the emerging outbreaks (Figure 1). However, 23.1% of EHDV outbreaks also occurred in low-risk areas, mostly at source sites, demonstrating that our model should be used primarily to estimate long-range dispersal, not short-range dispersal.
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