Prevalence of Heritable Symbionts in Parisian Bedbugs (Hemiptera: Cimicidae)

Like many insects, the biology of bedbugs is impacted by a range of partner heritable microbes. Three maternally inherited symbionts are recognised: Wolbachia (an obligate partner), Symbiopectobacterium purcellii strain SyClec, and Candidatus Tisiphia sp. (facultative symbionts typically present in some but not all individuals). Past work had examined the presence of these heritable microbes from established laboratory lines, but not from broader field samples. We therefore deployed targeted endpoint PCR assays to determine the symbiont infection status for 50 bedbugs collected from 10 districts of Paris during the 2023 outbreak. All three symbionts were found to be broadly present across Cimex lectularius samples, with the Symbiopectobacterium-Candidatus Tisiphia-Wolbachia triple infection most commonly observed. A minority of individuals lacked either one or both facultative symbionts. Five mtDNA haplotypes were observed across the COI barcode region, and triple infections were found in all mtDNA haplotypes, indicating that symbiont infection is not a recent invasion event. We conclude that the Parisian bedbug outbreak was one in which the host's secondary symbionts were present at high-frequency coinfections, and facultative symbionts are an important but uncharacterised component of bedbug populations.