Assessing the Phylogeographic Distribution of Candidatus Cardinium hertigii in Culicoides. Culicoides biting midge endosymbionts

Culicoides biting midges (Diptera: Ceratopogonidae), are the vectors of several viruses affecting livestock including bluetongue and Schmallenberg viruses. There are no effective control methods of the vectors, and disease control therefore relies on vaccines which, given the rapid emergence/spread of the viruses, are often not available. Thus, there is increasing interest in the heritable bacteria (endosymbionts) of invertebrates as they present novel targets for control initiatives. For example, the endosymbiont Wolbachia is capable of inducing a “virus blocking” phenotype in mosquito hosts. Previous studies on biting midges, have revealed infections with the endosymbiotic bacteria, Wolbachia and Rickettsia. Here we establish which Culicoides vector species are appropriate for further study of Cardinium-midge interactions. In addition, we establish associations between mitochondrial haplotypes (mitotypes), used as a phylogeographic marker, and Cardinium infection in the globally important vector C. imicola. The concordance of mitotypes and Cardinium infection in populations of C. imicola from different geographic regions suggests a potential confounding of future biodiversity studies which fail to consider the presence of Cardinium.