Genes show why bedbugs are resistant to insecticides

The blood-sucking bedbugs have become genetically wired to resist common pesticides, according to researchers who have sequenced the first complete genome of one of humanity's oldest and least-loved companions.
The study, led by researchers at the American Museum of Natural History and Cornell University in New York might lead to new ways to exterminate the unwelcome parasites.
"This work gives us the genetic basis to explore the bedbug's basic biology and its adaptation to dense human environments," said George Amato, director of the Museum's Sackler Institute for Comparative Genomics.
The common bedbug (Cimex lectularius) has been coupled with humans for thousands of years. This species is found in temperate regions and prefers to feed on human blood.

In recent decades, the prevalence of heated homes and global air travel have accelerated infestations in urban areas, where bedbugs have constant access to blood meals and opportunities to migrate to new hosts.
A resurgence in bedbug infestations since the late 1990s is largely associated with the evolution of the insects' resistance to known pesticides, many of which are not suitable for indoor application.

"Bedbugs all but vanished from human lives in the 1940s because of the widespread use of DDT, but, unfortunately, overuse contributed to resistance issues quite soon after that in bedbugs and other insect pests," said Louis Sorkin, from the Museum's Division of Invertebrate Zoology.

"Today, a very high percentage of bedbugs have genetic mutations that make them resistant to the insecticides that were commonly used to battle these urban pests. This makes the control of bedbugs extremely labour intensive," said Sorkin.
The researchers extracted DNA and RNA from preserved and living collections, including samples from a population that was first collected in 1973.
RNA was sampled from males and females representing each of the bug's six life stages, before and after blood meals, in order to paint a full picture of the bedbug genome.
Researchers found that the number of genes was consistent throughout the bedbug life cycle, but they observed notable changes in gene expression, especially after first blood meal.

Some genes, expressed only after the bedbug first drinks blood, are linked to insecticide resistance, including mechanisms that result in better detoxification and thicker chitin, or skin, researchers said.
This suggests that bedbugs are likely most vulnerable during the first nymph stage, potentially making it a good target for future insecticides.
The bedbug microbiome also contains more than 1,500 genes that map to more than 400 different species of bacteria, indicating that bed bugs harbour a rich suite of endosymbionts that are likely essential for their growth and reproduction.
This suggests that antibiotics that attack bacteria beneficial to bed bugs (but that are non-essential to humans) could complement control of the insects via pesticides.

The study was published in the journal Nature Communications.