Insectophobes beware: When bed bugs invade, the biggest mistake you can make is trying to kill them?

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Last summer, I had several red, swollen, itchy areas on my body, which were obviously different from mosquito bites. I suspected that they were caused by bedbug bites, but I searched the bed for a long time and found no trace of bedbugs. I bought an insect repellent sticker to put under the mattress, but I don’t know if it works (or maybe I bought it for psychological comfort).

Whenever I think of the fact that bed bugs can survive a year without food, I feel that it makes sense that this creature still exists after hundreds of millions of years of evolution. A few days ago, I read that the thermal death point of a certain bed bug reached an astonishing 45 degrees Celsius... Not only high temperatures, bed bugs are also amazingly adaptable to low temperature environments. Studies have shown that even in an environment of minus 15 degrees Celsius, bed bugs can still survive for more than 5 days.

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The stories have become all too familiar: rooms filled with bedbugs, blood-sucking bugs piled thickly on the floor. An airport closed its gates for deep cleaning after bedbugs were spotted. At Paris Fashion Week in 2023, bedbug detection dogs were put to work overtime as bedbugs appeared in movie theaters and on trains to fear and disgust.

Almost certainly due to global travel and poor pest management, bed bugs have made a comeback in more than 50 countries since the late 1990s. But the bug’s recent resurgence has come with an extra twist: When exterminators swarm the area to hunt the pests, they may encounter not just one, but two different kinds of bed bugs.

In addition to the temperate stink bug (Cimex lectularius), which has always been common in the Northern Hemisphere, its close relative, the tropical stink bug (Cimex hemipterus), is now found in temperate regions. Historically, this species never ventured that far from the equator, entomologists Stephen Doggett and Chow-Yang Lee wrote in the 2023 edition of the Annual Review of Entomology[1]. But in recent years, the tropical stink bug has appeared in the United States, Sweden, Italy, Norway, Finland, China, Japan, France, Central Europe, Spain, and even Russia. “This was unthinkable in the past,” said Chow-Yang Lee, a professor of urban entomology at UC Riverside.

Like common bed bugs, tropical bed bugs have become resistant to many standard insecticides, to the point that some experts say they generally wouldn't bother spraying their own homes if they were infested. The fight against bed bugs is estimated to cost the world economy billions of dollars each year.

© The Brussels Times

It all adds up to a sobering new reality: For many people, bedbugs are once again as much a part of life as they once were in human history. But as scientists race to find new strategies to combat these pests—from microfabrications of surfaces that ensnare the insects to fungal spores that invade and kill them—they’re also learning more about the bedbug’s quirky biology that could one day reveal the parasite’s Achilles’ heel.

Today, some bed bug species tolerate pesticide doses thousands of times higher than what would consistently kill them in the past.

Genomics shows that bedbugs emerged 115 million years ago, before the dinosaurs went extinct. When the first humans emerged and moved into caves, the ancestors of today's bedbugs were already well prepared. It's thought that these insects initially fed on the blood of bats. But bats' sleep-like coma-like state reduces circulation, which likely makes it harder for the blood-sucking parasites to feed. So it's likely that at least some of the bedbugs' ancestors were happy to switch to sucking human blood.

Since then, these bugs have followed humans around the world, traveling along ancient shipping routes and modern airplane flights. They have been found in well-preserved remains of ancient Egyptian workers’ dwellings dating back about 3,550 years.

Tropical stink bug. © Flickr

Bedbugs can survive a year or more without feeding. About the size of a squashed apple seed, they squeeze into cracks in walls or the seams of bed frames during the day; they crawl out at night, attracted by the carbon dioxide exhaled by sleepers and their body heat. In the early 20th century, an estimated 75% of homes in the UK had bedbugs. Over the years, some ridiculous bedbug control methods have circulated, including a recipe for "cat juice" from a 1725 pest control guide. The recipe called for suffocating and skinning a cat, then roasting it on a barbecue, mixing the dripping cat juice with egg yolk and oil, and smearing it into the cracks around the bed.

DDT and subsequent insecticides provided a few decades of respite from the 1940s to the 1990s, enough for most people to forget about the insects, to the point where they were unrecognizable when they reappeared at the turn of the century.

Doggett and Lee speculate that the bloodsuckers' re-entry began in areas of Africa where temperate and tropical bed bugs coexist naturally and where bedrooms were sprayed with DDT (and later other insecticides) to combat malaria-carrying mosquitoes. Initially, this probably killed most of the bed bugs, too. But some resistant individuals survived and began to reproduce.

Bed bugs change shape and color as they feed. © Colorado State University

Bed bugs can suck more than three times their body weight in blood. In the process, they also absorb any viruses or other infectious agents circulating in their prey, such as hepatitis B and HIV. Although they have not been found to transmit these pathogens in the wild, this does not mean that these parasites are harmless.

"Bedbug bites are among the most annoying of all insects," says Doggett, a medical entomologist at Westmead Hospital in Sydney, Australia. "If I get bit, I can't sleep because I'm so sensitive. If there are a lot of bedbugs, the bites are a nightmare." There have been cases of people accidentally setting their mattresses on fire in an attempt to get rid of bedbugs, and sometimes even burning down their homes.

Typical skin reactions to bed bug bites. © M & M Pest Control

Humans aren't the only ones who have such strong reactions. Bed bugs belong to the family Cimicidae, which includes about 100 species. Almost all of them prefer to bite non-human animals, such as birds. Biologists have observed that young cliff swallows would rather jump to their deaths from bedbug-infested nests than endure bedbug bites.

Hundreds of bed bugs may feast on beds at night, causing anemia in human sleepers and possible insomnia, anxiety and depression. They may find themselves shunned by friends, blacklisted by landlords and more prone to car accidents and mistakes at work due to lack of sleep.

At the very least, bed bugs may be indirectly contributing to human deaths. Doggett has noticed that some Africans have abandoned bed nets that protect them from mosquito bites that can cause deadly malaria because of bed bugs harbouring them in their beds. “In some areas, malaria cases are increasing, and we think bed bugs are playing a role in that,” he says.

The only bed bug sprays that are still relatively effective are certain combination products that mix different types of insecticides, but experts say it's only a matter of time before they become ineffective.

Bed bugs have been reported to be resistant to most insecticides to date, including organochlorines, organophosphates, carbamates, neonicotinoids, arylpyrroles, and pyrethroids. Some bed bug species today tolerate insecticides thousands of times higher than what would have consistently killed them in the past. Resistant bed bugs have either developed genetic mutations that prevent insecticides from effectively binding to their cells or have developed enzymes that quickly break down toxins in their bodies. Some bed bugs have grown thicker shells that prevent poisons from easily penetrating.

A survey of a Cleveland hospital several years ago found that new bed bugs were present every 2.2 days. And tropical bed bugs seem to be just as comfortable in our modern indoor environments as common bed bugs. "Heating and air conditioning have standardized our living environments," Lee says. "If a tropical bed bug is accidentally introduced into a house in Norway, it can even spend the winter there."

Bed bugs in hotel rooms evoke a strong reaction from travelers, with 60 percent saying they would change hotels if they found signs of bed bugs in their room, according to a survey conducted by researchers at the University of Kentucky. However, in the same survey, only 35 percent of business travelers and 28 percent of leisure travelers could correctly identify bed bugs among a list of common insects. © Entomology Today

Currently, the only bed bug sprays that are still reasonably effective are certain combination products that mix different types of insecticides, but experts say it’s only a matter of time before they become ineffective: reports of resistance have already been recorded.

More and more pest control experts are using nonchemical methods, such as heat treatments, in which trained professionals heat a room to more than 120 degrees Fahrenheit (48.9 degrees Celsius) for several hours. They sometimes sprinkle a powder called diatomaceous earth around the room, which clings to bed bugs that have taken shelter in wall cracks or under mattresses. The powder wears away the bed bug's outer shell, dehydrating it and killing it.

These measures, combined with greater awareness, have helped stabilize and even partially reverse the spread of bed bugs in some places. In New York City, for example, bed bug complaints dropped by half from 2014 to 2020, from an average of 875 complaints per month to 440.[2] However, this still translates to 14 complaints per day.

But nonchemical methods, while effective, tend to be slow to take effect. “It’s common for bed bugs to take one to two or even three months to be eliminated,” says Changlu Wang, an entomologist at Rutgers University. In the meantime, residents must continue to live in infested residences.

Non-chemical methods can also be expensive, as they require time-consuming and laborious steps, such as sealing cracks in walls and physically removing bed bugs by vacuuming. While a quick (but increasingly futile) spray of insecticides may cost a few hundred dollars, physical removal can run into the thousands. This puts effective bed bug control out of the reach of many people, leaving them more vulnerable to community-spreading bed bug infestations.

As a result, the epidemic has shifted to the poor, says Michael Levy, an epidemiologist at the University of Pennsylvania: “While many cities now have bedbug policies, few offer much help for those who can’t afford control.” In 2016, a survey of 2,372 low-income apartments in 43 buildings in four New Jersey cities found that between 3.8% and 29.5% were infested with bedbugs.

The northward spread of the tropical stink bug complicates matters further. Although the two species look similar, the tropical stink bug has special shin pads on its legs that allow it to crawl out of many of the smooth-walled traps used to monitor homes. That means an infestation can go undetected for a long time, Lee said. And the larger the stink bug population, the harder it is to get rid of an infestation.

To fight back, researchers are looking to traditional wisdom for inspiration. In the Balkans, residents used to spread leaves from the legume Phaseolus vulgaris L. around their beds. The leaves have tiny hooks on their surface that trap stink bugs. Now, scientists at the University of California, Irvine, are developing a “physical insecticide” that uses a synthetic material that mimics the microscopic hooks on bean leaves. “Once these bugs are pierced, they cannot escape,” wrote Catherine Loudon, a professor of biology at UC Irvine, in a 2022 paper in Integrative and Comparative Biology.[3]

Other recent approaches are rooted in nature. For example, scientists have found that essential oils can repel bed bugs. However, the effects are mostly temporary. Alternatively, certain fungal spores can work permanently. "Basically, the spores can get into the bed bug and kill it," Wang said. At least one product containing the insecticidal fungus, Beauveria bassiana, is now available in the United States.

Bed bugs killed by Beauveria bassiana. © Penn State

Researchers are still fascinated by the insect's biology, especially its sex life. Although female bed bugs have normal genitals, male bed bugs usually mate and inject sperm by piercing their needle-like genitals directly into the female's abdomen. They usually do this after the female has fed, as this would make her too full to defend herself.

Having to deal with these frequent injuries has led female bed bugs to evolve the only immune organ in the insect kingdom, says Klaus Reinhardt, a zoologist at Technische Universität Dresden in Germany. They have also evolved a very elastic material to cover the part of their abdomen where they are most likely to get stabbed. "It's similar to a self-sealing injection bottle that closes again when you pull out the needle," Reinhardt says.

While this knowledge may not do much to combat these pests directly, it may help answer another question: Why don't bed bugs stick to their hosts like lice do?

It turns out that bed bugs don't like our smell.

According to a 2021 study in Scientific Reports, certain lipids in human skin can repel these bed bugs. This causes them to retreat to their daytime hiding places while marking their paths with pheromones [4].

Exterminators have experimented with false trails to trap bed bugs. One day, we may be able to stop the spread of bed bugs by coating suitcases with a scent they hate.

Bed bugs are found in the seams of a sofa bed in L'Hay-les-Roses, near Paris, France, September 29, 2023. © Reuters/Stephanie Lecocq

But for now, caution is still the best approach. Experts advise that travelers check their accommodations for stains of bedbug defecation: in mattress seams and furniture and behind headboards (the insects poop dozens of times after each blood meal, often right next to their victims). Suitcases should be placed in hotel bathtubs or wrapped in plastic bags. Upon returning home, items in luggage should be placed in a dryer set on the highest temperature for at least 30 minutes, or in a refrigerator at very low temperatures for several days.

If bed bugs do invade a home, "the biggest mistake is to try to eliminate them yourself," Doggett said. "The average person doesn't realize how difficult it is to control bed bugs, and they use pesticides from the supermarket that are labeled for bed bugs but don't work. The infestation will spread, and the costs will escalate."

By Ute Eberle

Translated by tim

Proofreading/Rabbit's Light Footsteps

This article is based on the Creative Commons License (BY-NC) and is published by tim on Leviathan

The article only reflects the author's views and does not necessarily represent the position of Leviathan