Abstract
A frightening resurgence of bed bug infestations has occurred over the last 10 years in the U.S. and current chemical methods have been inadequate for controlling this pest due to widespread insecticide resistance. Little is known about the mechanisms of resistance present in U.S. bed bug populations, making it extremely difficult to develop intelligent strategies for their control. We have identified bed bugs collected in Richmond, VA which exhibit both kdr-type (L925I) and metabolic resistance to pyrethroid insecticides. Using LD50 bioassays, we determined that resistance ratios for Richmond strain bed bugs were ∼5200-fold to the insecticide deltamethrin. To identify metabolic genes potentially involved in the detoxification of pyrethroids, we performed deep-sequencing of the adult bed bug transcriptome, obtaining more than 2.5 million reads on the 454 titanium platform. Following assembly, analysis of newly identified gene transcripts in both Harlan (susceptible) and Richmond (resistant) bed bugs revealed several candidate cytochrome P450 and carboxylesterase genes which were significantly over-expressed in the resistant strain, consistent with the idea of increased metabolic resistance. These data will accelerate efforts to understand the biochemical basis for insecticide resistance in bed bugs, and provide molecular markers to assist in the surveillance of metabolic resistance.
Highlights
The common bed bug, Cimex lectularius (Hemiptera: Cimicidae) was a well established pest in the United States, and other developed nations, at the turn of the 20th century
PCR-based methods are preferred to screen large numbers of individuals/populations for a defined trait such as a nucleotide polymorphism or for differences in gene expression levels, which are strongly associated with a resistance phenotype. While such a diagnostic PCR method has been developed for surveying target site resistance [8], no such assays have been associated with metabolic resistance in bed bugs. We present both biochemical and genetic evidence that bed bug populations collected in Richmond, VA carry both target site and metabolic resistance traits, and these correlate with,5200fold resistance to the pyrethroid deltamethrin
We previously demonstrated that bed bugs collected in Richmond, VA display a greatly extended time to mortality when exposed to formulated deltamethrin (0.06%) and permethrin (0.05%) [17]
Summary
The common bed bug, Cimex lectularius (Hemiptera: Cimicidae) was a well established pest in the United States, and other developed nations, at the turn of the 20th century. While DDT was initially effective for bed bug control, resistance to the cyclodienes was well documented among different bed bug populations by 1958 [1,2]. The National Pest Control Association’s initial recommendation for combating DDT-resistant bed bug populations was malathion (as reviewed by [3]). While malathion further reduced the incidence of bed bug infestations in developed nations, bed bugs had developed resistance to organophosphate insecticides, including malathion by the 1960s [4]. Attempts to characterize the mechanisms of resistance in these resurgent bed bug populations have followed. Yoon et al [7] found that resistance to deltamethrin in a bed bug strain from New
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