Host Specialisation in the Common Bed Bug (Cimex lectularius): Genetic Characterization of the Bat and Human Lineages

Background: After its nearly eradication in the 1940’s, the bed bug ( Cimex lectularius ) experienced a global resurgence with some populations displaying insecticide resistance. Two distinct lineages of bed bugs have been identified, one of which is associated with humans and the other with bats. Given that bat roosts can be shared within human shelters, investigating host specialisation in bed bugs is essential to gain a better understanding of the potential risks of cross-species transmission. Methods We analysed and compared the genetic composition of human and bat-associated bed bugs. We first conducted a median-joining analysis based on COI and 16S rRNA mitochondrial genes to detect any host-specific separation of haplotypes. Then, using 10 microsatellites, we estimated the genetic diversity and structure between and within the two hosts-associated bed bugs. Finally, we carried out an analysis of knock-down insecticide resistance gene variants to assess the difference in resistance of the host-associated common bed bugs to pyrethroid insecticides. Results The median-joining analysis shows a clear separation of all haplotypes that are host-specific. Consistently, the analysis of genetic structure reveals two genetic clusters associated with bats and humans with some structure among human-associated sites. Human-associated bed bugs might have settled from multiple colonisation events or undergone bottlenecks. This separation is also supported by the analysis of knock-down insecticide resistance gene variants which shows that bed bugs infecting humans have evolved insecticide resistance in contrast to the ones infecting bats. Conclusion Taken together, our results show that bed bugs seem to have evolved into genetically differentiated lineages specialised on different hosts, thus supporting the hypothesis of host specialisation in the common bed bugs.