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By the 1960s, widespread pesticide use had nearly eradicated bed bug populations. In the past two decades, however, these persistent pests have made a troubling resurgence. Now, scientists have uncovered genetic factors that shed light on their growing resistance to insecticides.

A team of researchers led by Hidemasa Bono of Hiroshima University has sequenced the most complete insecticide-resistant bed bug genome to date and compared it to the genome of a non-resistant bed bug. Their findings, detailed in a study published in the journal Insects in September, offer unprecedented insights into the genetic mutations driving insecticide resistance in bed bugs, which could shape future pest control strategies.

Bed bugs are notorious for being a serious nuisance. While they are not known to transmit diseases to humans, their bites can lead to itching, sleep loss, anxiety, and, in some cases, allergic reactions, according to the Centers for Disease Control and Prevention (CDC). Excessive scratching can also result in secondary skin infections.

“We identified a large number of genes likely involved in insecticide resistance, many of which have not been previously reported as being associated with resistance in bed bugs,” said Kouhei Toga of Hiroshima University, the study’s first author, in a university statement.

The researchers analyzed the genomes of two groups of bed bugs: non-resistant specimens descended from wild bed bugs captured over six decades ago in Nagasaki, and resistant specimens descended from bed bugs found in a Hiroshima hotel in 2010. Using a “breakthrough” method called long-read sequencing, which enables the sequencing of longer DNA sections with fewer gaps, the team mapped both genomes with near-gap-free and near-error-free precision.

When comparing the two genomes, the researchers identified hundreds of mutations associated with insecticide resistance. Notably, they found that the genome of the hotel bed bugs was 19,859 times more resistant to pyrethroids—a common synthetic pesticide—than the non-resistant genome.

“We determined the genome sequence of insecticide-resistant bed bugs, which exhibited 20,000-fold greater resistance compared to susceptible bed bugs,” said Toga. “By comparing the amino acid sequences between the susceptible and resistant bed bugs, we identified 729 transcripts with resistance-specific mutations.” These transcripts are RNA molecules that translate DNA instructions into proteins.

The study not only confirmed resistance mutations found in previous research but also uncovered new ones. “These transcripts included genes related to DNA damage response, cell cycle regulation, insulin metabolism, and lysosome functions. This suggests that these molecular pathways may play a role in the development of pyrethroid resistance in bed bugs,” Toga explained. Lysosomes are organelles in animal cells that contain digestive enzymes.

By identifying these mutations, the study provides valuable genetic resources to monitor, understand, and address insecticide resistance in bed bug populations—both in the wild and in our homes. This research is especially relevant in preventing scenarios like the Paris 2023 bed bug outbreak from recurring.