Detection of Low-Level Cardinium and Wolbachia Infections in Culicoides
ABSTRACTBacterial endosymbionts have been identified as potentially useful biological control agents for a range of invertebrate vectors of disease. Previous studies ofCulicoides(Diptera: Ceratopogonidae) species using conventional PCR assays have provided evidence ofWolbachia(1/33) andCardinium(8/33) infections. Here, we screened 20 species ofCulicoidesforWolbachiaandCardinium, utilizing a combination of conventional PCR and more sensitive quantitative PCR (qPCR) assays. Low levels ofCardiniumDNA were detected in females of all but one of theCulicoidesspecies screened, and low levels ofWolbachiawere detected in females of 9 of the 20Culicoidesspecies. Sequence analysis based on partial 16S rRNA gene andgyrBsequences identified “CandidatusCardinium hertigii” from group C, which has previously been identified inCulicoidesfrom Japan, Israel, and the United Kingdom.Wolbachiastrains detected in this study showed 98 to 99% sequence identity toWolbachiapreviously detected fromCulicoidesbased on the 16S rRNA gene, whereas a strain with a novelwspsequence was identified inCulicoidesnarrabeenensis. Cardiniumisolates grouped to geographical regions independent of the hostCulicoidesspecies, suggesting possible geographical barriers toCardiniummovement. Screening also identifiedAsaiabacteria inCulicoides. These findings point to a diversity of low-level endosymbiont infections inCulicoides, providing candidates for further characterization and highlighting the widespread occurrence of these endosymbionts in this insect group.