Bed bugs
by health researcher and writer SOFIA QUAGLIA - June 2024

When bloodthirsty bed bugs made headlines for infesting Paris Fashion Week in 2023, it shone a spotlight on a problem that’s been making experts itch for decades: the arms race going on between bed bugs and humans. Now, with the 2024 Summer Olympics fast approaching, the stakes are higher than ever
e d bugs have been around longer than humans. When researchers used bed bug DNA to get an idea of when they first evolved, they found that the ancestors of today’s bed bugs were already tiny but successful predators over 115 million years ago, during the reign of the dinosaurs.

What they were preying on back then, we don’t know, possibly ancient birds. What we do know is that when the first bats appeared, bed bugs were present. A few enterprising individuals crawled into the caves where bats slept to enjoy a hearty meal. From there, several species of bed bugs evolved to feed on their blood, according to the research of Prof Klaus Reinhardt, an evolutionary biologist at University of Tübingen, Germany.
As early humans took shelter in those same caves, bed bugs suddenly found they had a larger, juicier mammal to feed on.

 

Somewhere between 900,000 and 100,000 years ago (Reinhardt reckons 245,000 years ago) bed bugs added humans to their roster of victims – a unique move for a parasite, which usually thrive by being highly specialised to one type of host.
The oldest recorded proof of bed bugs that mingled with humans are the 11,000-year-old bugs archaeologists found in caves in North America. There are also fossilised tracks left by bed bug ancestors in ancient Egyptian workers’ living quarters from 3,550 years ago, as well as Greek comedy texts from 423 BCE with characters saying “What a torture the bugs will this day put me to.”

Today there are about 100 species of bed bugs, all part of the insect family, known as Cimicidae. They’re wingless, six-legged, rust-coloured, and the size and shape of an apple seed. They’re also obligated-blood feeders, meaning they can only feed on the blood of warm-blooded animals. But only three of these 100 species have a penchant for human blood: the common bed bug (Cimex lectularius), the tropical bed bug (Cimex hemipterus) and the West African bed bug (Leptocimex boueti). All three of these species still also feed on birds and bats, because they never specialised completely.

While the common bed bug is the most widespread, the rounder and chubbier tropical bed bugs have recently started showing up all over the northern hemisphere, according to Prof Chow-Yang Lee, chair of urban entomology at University of California, Riverside. They’ve crept all the way to Norway, Sweden and Finland – corners of northern Europe once thought too cold for the vampiric critters, but now made hospitable thanks to warming global temperatures and modern amenities like controlled household heating. “Of course, global travel contributes tremendously to this spread,” says Lee.

For most of the day, the blood-thirsty insects hide in the nooks and crannies of our homes, hotel rooms, hospitals and university dorms, seeking shelter and shying away from human interaction. But when we lay down to rest at night, they come out of hiding, lured by the warmth of our bodies and the carbon dioxide we exhale. (There’s nothing stopping bed bugs from biting during the day if they’re hungry.) They perch on our bodies and puncture our skin with their straw-like beaks, then suck blood out while injecting anaesthetic and anticoagulant chemicals to allow the feeding to go ahead unnoticed.

While bed bug bites don’t transmit any diseases – like those of bloodsucking ticks or mosquitoes can – they do leave a nasty, itchy bump on human skin and make it increasingly hard to sleep. Some people describe the bites as “hardened, ping-pong-ball-sized welts that itch for over a week.” Studies show that bed bug infestations can leave victims with long-lasting depression, paranoia, hyper-vigilance and obsessive thoughts.

Something about our musty scent lures the bugs in. When researchers at the University of Sheffield put bed bugs in a room with a pile of dirty clothes, the insects emerged looking for a feed more often than they did if the clothes were clean. (Experts say this may explain how bed bugs travel internationally, by finding refuge in the laundry of travellers.) But similar experiments suggest something about the fatty molecules in our skin also repels the bed bugs once they’ve fed – after a few minutes, the bug will have had its fill, with three to four times its body weight in blood, and leave to digest its meal, rather than live on the host like a tick or flea.

THE CIRCLE OF LIFE
Right after feeding is also the best time for bed bugs to mate, because the females are lethargic from their feast and so less likely to rebel when males force them into intercourse. Although females have the equivalent of a bed bug vagina, males prefer to jab their equivalent of penises straight into the females’ abdomens and release their sperm there. To cope with this, female Cimex have evolved a special organ, known as a spermalege or ‘organ of Berlese’, to quickly seal the wound and deal with the sperm. Despite this traumatic insemination method, they have a prolific sex life, reproducing every two months and laying up to 500 eggs a lifetime. The eggs take up to 10 days to hatch into beige nymphs that shed their skin five times in seven weeks before reaching maturity.

Interestingly, although inbreeding usually leads to mutations and unhealthy offspring in most animals, it holds no such dangers for bed bugs, according to Schal. “One mated female can start a whole population,” says Schal. Scientists have made brothers and sisters mate for up to 30 generations with nothing but health and prosperity.

Cross-breeding different populations actually doubles their fertility. When researchers marked and tracked a select few insects from large bed bug populations in six infested flats, they found there were anywhere from 2,400 to 14,000-plus bed bugs in each home. It took the colonies just two weeks to spread into the 24 adjoining flats in the building and bed bugs were still present and active more than five months after the human residents had abandoned the premises.

This promiscuity allows for bed bug infestations to propagate easily. By the 1760s, bed bug infestations in Europe’s hospitals were so bad that a British surgeon described them as “frequently a greater evil to the patient than the malady for which he seeks a hospital.” Hotel owners suggested guests drink themselves to sleep to bear the itch. Some travellers journeyed with pigs and made the animals rest in bed before them each night, so the bugs would be satiated by the time the gentlemen lay down. By the 20th century, more than 75 per cent of homes in the United Kingdom had bed bugs.

People have tried all sorts of tricks to eradicate them over the decades. Some thought hanging the feet of a hare or stag on the bed would keep bed bugs at bay, while others resorted to a lighted candle in the middle of a slice of bread sticky with glue. The most desperate cases have seen people try spraying arsenic and mercury, which are toxic to humans; homes have even been burned down in a bid to get rid of an infestation.

It took until the 1930s for scientists to discover potent chemical insecticides such as dichlorodiphenyltrichloroethane (DDT) and organophosphates, turning the tide on what, up to then, had largely been a losing battle.
DDT was so potent and lasted for so long that it reduced bed bug populations in a jiffy. Their numbers dropped so drastically that, from the early 1950s to the late 1990s, people in developing countries thought the bloodsuckers were no longer a problem. But some bugs were adapting in the face of this new adversity. They had already started developing resistance to the powerful insecticide sprays as early as 1948; a resistance that only grew in strength over the subsequent years.

When DDT was banned in 1972 due to its toxicity to humans, bed bugs made a comeback and, by the early 2000s, their populations were growing again with a vengeance.
“By then, when the pest controllers came across bed bugs they had no training [in how to handle them]. They didn’t know anything about their biology; they were as ignorant as anybody else,” says Nina Jenkins, professor of entomology at Penn State University. “It took them by surprise.”

CHEMICAL WARFARE
Since then, bed bug populations have been growing and growing. According to ANSES, the French Agency for Food, Environmental and Occupational Health & Safety, 11 per cent of households in France were infested by bed bugs between 2017 and 2022. Hence, the Paris Fashion Week fiasco in 2023 was just a snapshot of a very real, very growing trend that’s been hundreds of years in the making. The increased travel to the French capital for the event, and the media frenzy surrounding the scandal shone a light on a problem that’s long been lurking in the cracks – literally.

Now, bed bugs are resistant to most of the chemicals designed to kill them, like carbamates, neonicotinoids and pyrethroids. “Insecticide resistance is real,” says Lee. “We’ve seen populations of bed bugs that are more than 10,000 times resistant to insecticide. You can practically dip the bugs in the insecticide solution and they’ll still be alive afterwards.”

Cimex have developed harder outer shells so that insecticides can’t easily permeate into their organs; they’ve evolved gene mutations that make them immune to the specific toxins in those products; and they’ve amped up the enzymes that break down the insecticides if they do get inside their bodies, according to Dini Miller, professor of urban pest management at Virginia Tech.
“We’ve selected for what I like to call ‘hard-drinking bed bugs’,” says Miller. “Just like some people can stay awake while drinking alcohol all night and be fine while others pass out, well, these are the bed bugs that have enough enzymes to stay awake and drink all night.”

As a result, there are very few pest control methods that can get around these super-powered bed bug evolutions, and better methods are still a long way off. “We’re pretty much having to hit every single bed bug with a hammer to get rid of it,” says Miller.
Powerful chemical pesticides that combine various types of bug killers are holding on in the market, but it’s likely Cimex is already developing resistance to those too. Some scientists are inventing slippery tape to wrap around our beds so the bugs can’t crawl up onto our sheets; others are trying sticky bed legs so the bugs get stuck along the way. One tech company has designed smart hotel bed legs that collect bed bugs and send a text message alert to the hotel staff. But these methods are hardly versatile enough for large infestations.

Bed bug baits that could be placed around the house, like rat or cockroach traps, are being developed in Schal’s lab. But since the bugs aren’t attracted to the tangy scent of cheese or the sweet smell of leftover cake, recreating the perfect combination of human odour, heat and exhaled breath they love has proven a difficult task. “The challenge is to develop an artificial human,” says Schal – a lure attractive enough to entice the bugs out of hiding, with a skin-like membrane for them to sink their beaks into, and the right type of deadly liquid for them to consume that’s a convincing blood substitute. (Boric acid might do the trick, Schal thinks, since a one-per-cent solution of it is enough to poke holes through bed bugs’ digestive systems, according to his experiments.)

We could also go from treating the environment to treating the host, just like we went from spraying anti-flee medication to giving our pets pills to rid them of the parasites. “We call them drugs, but they’re basically insecticides,” says Schal. This sort of medical solution to the problem is being tested in bed bug-infested poultry farms, but it’ll take at least 10 years before scientists can test and approve a tablet that works for bed bugs and doesn’t intoxicate humans. “We still have a lot to learn about the basic biology of bed bugs to find their weak links,” says Schal.
 

NATURAL REMEDIES
One of the most promising bed bug countermeasures harnesses the power of an insect-killing fungus called Beauveria bassiana. This fungus is a parasite to bed bugs and, once its spores come into contact with a bed bug’s moisture, it seeps into the cracks of its shell and spends the next 10 days growing inside its body. “It buds off and uses all of the nutrients inside the blood of the bed bug to feed itself,” says Jenkins, who developed the product. “So the bed bug dies of starvation and dehydration.”

Although Jenkins had spent several years studying the fungus, which is already widely used in agriculture, she was surprised to find it worked so quickly when she tested it on bed bugs. “Bed bugs did die the quickest we’ve ever seen any insect die from Beauveria,” she says. “It’s amazing.”

The fungal spores can be sprayed as a thin, oily boundary around a bed. When the bugs cross it they become infected with the fungus and take the spores back to their nests and spread the disease to their entire colony.
But while this kills the bugs crawling onto your bed each night, it doesn’t stop them from hitching a ride on something you might be taking into bed with you. After successful Beauveria  treatments, people have managed to reintroduce bed bugs in their sheets by bringing infested plush toys, books or even guns to bed, says Jenkins.

Some old-fashioned techniques still work, too. Heat is one: adults and eggs die between 48 and 54°C (118 and 130°F) so putting infested clothes and bedding in the dryer at maximum heat for a couple of cycles will do the job. Some exterminator companies heat entire homes to eradicate colonies, but ensuring every crevice in a house reaches such high temperatures for long enough to kill bed bugs is hard work, says Miller, not to mention expensive. Professional fumigation is effective, but also expensive and most people can’t afford to leave their homes for several days while the procedure is underway. Furthermore, you can’t fumigate a single flat; if you live in a block, the whole building has to be fumigated.

Nevertheless, getting professionals involved is the top recommendation for handling bed bug infestations. It’s these practical and economic barriers that perpetuate the bed bug crises, which, according to the experts, often leaves elderly and low-income people out on a limb because they don’t have the means to address the problem.

Bed bugs don’t discriminate: blood is blood, whether the person it comes from is wealthy or not. But they’re less of a problem for wealthy people as they can afford to pay pest controllers to get rid of them. And since bed bugs don’t transmit diseases, as other bloodthirsty insects do, local and national governments don’t tend to put a lot of effort into developing strategies to tackle the problem for people who can’t afford to do so on their own.

“The worst cases are where the bugs are affecting people who are disadvantaged and who can’t afford any form of control,” says Lee. “These people are basically left to get eaten alive.”
This means that bed bugs are never totally exterminated: pockets of the population have constant, ongoing infestations, and from those hotspots, the bed bugs can re-infest places they’ve been eradicated from all over again. Addressing bed bugs as a public health issue is the only way out, Lee says.

“This problem will continue until, finally, one day, we regard bed bugs as a community problem, rather than as an individual problem.”