Fight Bedbug Infestations: Guide insecticide treatments and develop alternative control methods – FBI

Bedbugs feed on blood exclusively during the night. Reactions to bites can be severe, and the psychological impact of bed bugs is significant. Despite their limited ability to actively disperse, bedbugs colonize new areas extremely quickly due to human movement. A resurgence of bedbug infestations has been observed in the United States, Europe, Asia, Africa and Australia since the 1990s. In France, more than 700,000 sites are infested, and this number has been increasing dramatically every year for the past ten years (nearly 5 million French infested since 2016). Personal housing but also collective housing (retirement homes, hospitals, nurseries or prisons) are particularly prone to infestations, which makes bedbugs a public health problem. Hotels or cinemas are not spared, which makes bedbug infestations a major economic problem for the tourism industry.
Their recent resurgence is mainly related to the evolution of resistance to insecticides, especially pyrethroids. Mutations affecting sodium channels, insecticide detoxification or sequestration mechanisms and cuticle thickening have been described, but their relative contribution to the overall resistance phenotype and their molecular basis remain poorly resolved, hampering their monitoring and insecticide management in the field. We therefore plan to analyze the diversity, distribution and phenotypic contribution of genetic determinants underlying pyrethroid resistance in bedbugs on a European scale. These results will allow us to develop rapid diagnostic tools for resistance genes in the field, in order to target the use of specific pesticides. This targeted use of insecticides will allow to preserve their efficiency until more environmentally friendly methods are developed.
It is therefore urgent to develop alternative and complementary methods to circumvent the use of insecticides. This is especially true for bed bugs, where insecticide treatment must be done in homes, increasing human exposure to these products and their non-targeted effects. Interestingly, bedbugs harbor a nutritional symbiont: intracellular bacteria of the genus Wolbachia. These bacteria supply the bedbugs with B vitamins - which are scarce in the blood - to such an extent that neither the insect nor the symbiont can now survive independently. The development of specific control methods based on the disruption of this obligate symbiosis is not yet possible, as the biology of this interaction remains relatively poorly understood. We therefore propose to characterize precisely the dialogue between bedbugs and their obligate symbiont, using transcriptomics and metabolomics approaches, complemented by functional validation of candidates. In particular, we will study the mechanisms involved in the maintenance and control of the symbiotic population, and the molecular and metabolic mechanisms involved in nutritional dependence. These studies will aim at developing in the longer-term prototypes of specific control methods, based on the disruption of the symbiotic association.
Finally, because insecticides can have a direct impact on Wolbachia populations, and conversely symbionts can have an impact on the survival of bugs in the presence of insecticides (e.g., insecticide detoxification), we will characterize the interference between Wolbachia and insecticides in the context of optimizing the efficacy of both control methods, alone or in combination.