Abstract
Culicoides imicola, an Afrotropical biting midge species, is historically known to transmit orbiviruses of veterinary importance, including bluetongue virus (BTV), epizootic haemorrhagic disease virus, and African horse sickness virus. Distributed around the Mediterranean basin, C. imicola was first recorded in France in September 2000 on the Mediterranean island of Corsica, shortly before the emergence of BTV serotype 2 in October 2000. Three years later, individuals were collected on the French mainland in the Var and Alpes-Maritimes departments. Unexpectedly, a small population was also observed in the Pyrénées-Orientales department near Spain between 2008 and 2012.Since its initial detection on mainland France, annual entomological surveillance using OVI traps has been conducted at the end of summer to (i) investigate the spatial distribution along the French Mediterranean coast and (ii) monitor abundance peaks over time.Twenty years of surveillance data, associated with results of genetic studies, reveal passive dispersal of C. imicola individuals from Corsica to mainland, and that C. imicolamaintains a stable yet sparse distribution on the French Mediterranean coast, in contrast to its higher abundance in Corsica. The population of the Pyrénées-Orientales department appears to have collapsed after 4 years of limited distribution and low abundance. As the northernmost known population, it is hypothesized that the French continental C. imicola population has struggled to adapt to local environmental and climatic conditions, thus limiting until now its potential for further northern expansion.