Pushed to the brink of extinction, bed bugs have adapted — and now pesticides are almost useless against these insects, which have returned stronger, smarter and more resilient than ever. What happened?
In the 1960s, bed bugs seemed doomed. After centuries of living in the shadow and torment humanitywe were very close to eradicating them.
Our main weapon was pesticides like DDT and pyrethroids, which proved to be devastatingly effective. But today these little pests are back — stronger, smarter and more resilient than ever.
What happened?
The resurgence of bed bugs has become a global headache as infest homes, hotels and public spaces.
Recent investigations have revealed that bed bugs, Cimex lectulariusdeveloped a series of sophisticated genetic defenses. These defenses make us almost invincible against the chemicals that, at one time, seemed to lead to its extinction.
But the authors of a new study, recently published in the journal Insects, sequenced the bed bug genomediscovering what they are still vulnerable to.
Mutation and adaptation
The chemical attack on pests began in earnest after World War II. The infamous DDT, or dichlorodiphenyltrichloroethaneand other synthetic pesticides have been sprayed freely in homes, hotels and public buildings.
Bedbugs, which feed on human blood and hide in crevices, seams and mattresses, were vulnerable to these chemicals. For a brief period, the world lived in an era almost without bedbugs, recalls .
But This victory was short-lived. In the 1990s and 2000s, reports of bed bug infestations began to rise again. Hotels in big cities have faced waves of complaints.
This time, however, the bedbugs were different and turned out to be more and more. The pesticides that had once worked wonders had barely slowed them down.
“Bed bugs have expanded globally over the past two decades, causing numerous health risks. To the mutations in your genes allowed bed bugs to develop insecticide resistance“, write the authors of the study.
The researchers, led by Bonus Hidemasa at Hiroshima University, sequenced the genomes of bed bugs susceptible and resistant to pesticides, and found hundreds of specific genetic mutations of resistant bed bugs.
These mutations were not random. They offered resistance to pyrethroids – the pesticide most used today against bedbugs.
Annoying insects
Bedbugs are micropredators that feed on blood, usually at night. Do not transmit diseases to humansbut its bite can cause rashes, blisters and allergic reactions.
What we call “bedbugs” are actually two species: Cimex lectularius (the common stink bug) and Cimex hemipterus, which are found mainly in the tropics.
They have been with us for thousands of years. Bed bug fossils have been found in Egypt dating back more than 3,500 years.
In recent years, they have become so resistant to pesticides that experts often recommend non-chemical control methods — in other words, the best way to get rid of bed bugs is vacuum and throw them away. The second best option is remove all fabrics and wash them to more than 60 degrees Celsius.
There is no evidence that a combination of methods Non-chemical insecticides are more effective than non-chemical methods alone.
Bed bug colony (Cimex lectularius) in mattress
The resistance It didn’t happen overnight. It evolved over decades, driven by the inefficient use of pesticides. Sometimes a bed bug population has been exposed to pesticides, but some individuals have survived.
These survivors reproducedpassing its resistance genes to the next generation. Repeated exposure to pesticides acted as a filter, allowing only the most resistant bed bugs to develop.
Possibly, resistant strains dominated the population. This process, known as “selective pressure“, is a classic example of evolution in action.
“We determined the genome sequence of insecticide-resistant bed bugs, which had a resistance 20,000 times greater than that of susceptible bed bugs”, explains the first author of the study, Kouhei Togaresearcher at Hiroshima University.
“By comparing the amino acid sequences between susceptible and resistant bed bugs, we identified 729 transcripts with specific mutations of resistance”, explains the researcher.
What has changed?
Sequencing a genome is a bit like put together a huge puzzleoften with millions and millions of pieces. The main advance in this case was the long-read sequencing method, which allows long chains of DNA or RNA to be sequenced at once, without dividing them into smaller fragments.
The researchers obtained an almost complete image of the two genomes of resistant and non-resistant insects, reaching a coverage of around 98% for the first and 95% for the second.
One of the main discoveries was the role of sodium channels voltage dependent. These channels are critical for nerve function and pyrethroids work by disrupting them, causing paralysis and death.
However, resistant bed bugs had mutations in these channels sodium, making them less vulnerable to the effects of the pesticide. Essentially, the pesticide he could no longer “stick” to his target.
In addition to sodium channels, the study identified changes in genes related to other defense mechanisms.
Some mutations increased the ability of bed bugs to metabolize (and detoxify) chemicals faster. Other of these mutations thickened the exoskeletonpreventing pesticides from penetrating the body.
Together, these two adaptations formed a formidable shield against chemical attacks that until a few years ago proved to be devastating for the species.
Some bed bugs had mutations in genes associated with acetylcholinesterase, an enzyme targeted by organophosphate and carbamate pesticides. These mutations further expanded the bedbug arsenal against different classes of chemicals.
Researchers now hope this study can help us develop most effective pesticidesidentifying the exact genetic mutations that confer resistance to bed bugs — and allowing us, once again, to have a restful night’s sleep without fear of having the company of unwanted guests.
