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Title: Colonization of the Mediterranean Basin by the vector biting midge species Culicoides imicola: an old story

Author
item JACQUET, S - Centro De Cooperation Internationale En Recherche Agronomique Pour Le Development (CIRAD)
item GARROS, C - Centro De Cooperation Internationale En Recherche Agronomique Pour Le Development (CIRAD)
item LOMBAERT, E - Centro De Cooperation Internationale En Recherche Agronomique Pour Le Development (CIRAD)
item WALTON, C - University Of Manchester
item RESTREPO, J - Centro De Cooperation Internationale En Recherche Agronomique Pour Le Development (CIRAD)
item ALLENE, X - Centro De Cooperation Internationale En Recherche Agronomique Pour Le Development (CIRAD)
item BALDET, T - Centro De Cooperation Internationale En Recherche Agronomique Pour Le Development (CIRAD)
item CETRE-SOSSAH, C - Centro De Cooperation Internationale En Recherche Agronomique Pour Le Development (CIRAD)
item CHASKOPOULOU, ALEXANDRA - European Biological Control Laboratory (EBCL)
item DELECOLLE, JC - Institute Of Parasitology - Germany

Submitted to: Molecular Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/1/2015
Publication Date: 11/1/2015
Citation: Jacquet, S., Garros, C., Lombaert, E., Walton, C., Restrepo, J., Allene, X., Baldet, T., Cetre-Sossah, C., Chaskopoulou, A., Delecolle, J. 2015. Colonization of the Mediterranean Basin by the vector biting midge species Culicoides imicola: an old story. Molecular Ecology. 24(22):5707-25.

Interpretive Summary: Culicoides is a genus of biting midges in the family Ceratopogonidae that can be annoying pests of humans and animals (wild and domestic). In addition to the discomfort they cause biting midges serve as vectors of viruses, protozoans and nematodes. One of the most important diseases caused by Culicoides midges is Blutongue (BLU) disease occurring in many part of the world including temperate and southern regions of North America, parts of Central America and South America bordering the Caribbean, Europe, the Middle East, Asia, Australia, and Southern Africa. Bluetongue disease is caused by an orbivirus in the family Reoviridae which infects ruminants and specifically sheep and cattle. It is known to occur throughout most of the southern and western US, where prevalence of antibody to BLU virus in cattle is commonly 20-50%. The aim of the work described in this manuscript is to increase our understanding of the demographic history and genetic make-up of colonizing Culicoides species in order to design accurate control measures in areas newly colonized by vector species of economically important pathogens.

Technical Abstract: Understanding the demographic history and genetic make-up of colonizing species is critical for inferring population sources and colonization routes. This is of main interest for designing accurate control measures in areas newly colonized by vector species of economically important pathogens. The biting midge Culicoides imicola is a major vector of Orbiviruses to livestock. Historically, the distribution of this species was limited to the Afrotropical region. Entomological surveys first revealed the presence of C. imicola in the south of the Mediterranean basin by the 1970’s. Following recurrent reports of massive bluetongue outbreaks since the 1990s, the presence of the species was confirmed in northern areas. In this study, we addressed the chronology and processes of C. imicola colonization in the Mediterranean basin. We characterized the genetic structure of its populations across Mediterranean and African regions using both mitochondrial and nuclear markers, and combined phylogeographical analyses with population genetics and approximate Bayesian computation. We found a west/east genetic differentiation between populations, occurring both within Africa and within the Mediterranean basin. We demonstrated that three of these groups had experienced demographic expansions in the Pleistocene, probably because of climate changes during this period. Finally, we showed that C. imicola could have colonized the Mediterranean basin in the late Pleistocene or early Holocene through a single event of introduction; however we cannot exclude the hypothesis involving two routes of colonization. Thus, the recent bluetongue outbreaks are not linked to C. imicola colonization event, but rather to biological changes in the vector or the virus.