Molecular taxonomy and population structure of a Culicoides midge vector

The biting midge Culicoides imicola Kieffer (Diptera: Ceratopogonidae) is the major Old World vector of the arboviruses that cause African horse sickness (AHS) and bluetongue (BT). Recently, the incidence and geographical scales of AHS and BT outbreaks in the Mediterranean Basin have increased, with serotype distribution in the BT outbreaks being geographically structured. The authors review molecular approaches for assessing the contribution of cryptic species and population subdivision in C. imicola to BT serotype structure in this region. No evidence was found for cryptic species. In contrast, evidence was found for marked matrilineal subdivision between the eastern and western parts of the Mediterranean Basin. This pattern is comparable to the geographic structure of BT serotypes, suggesting that subdivision in the insect vector potentially constrains serotype spread. The authors are presently testing this hypothesis.