Many countries have seen a surge in infestations of the bloodsucking pest over the past decade. Brooke Borel examines what’s needed to tackle the re-emerging threat.
Nothing makes the skin crawl more than the idea that tiny bloodsucking bugs could be living in our bedrooms. Around the size of a lentil, the common bed bug*, Cimex lectularius, can drink up to seven times its own weight in blood in one feeding, leave nasty, itchy bumps on their human hosts, and hide unseen for months on end.
Since the late 1990s, the bed bug has become an increasingly common urban nuisance in homes and hotels worldwide. A 2010 survey from the University of Kentucky and the National Pest Management Association found that 95% of US pest control companies had treated a bed bug infestation in the previous year, up from 25% a decade before, and 11% before that. Only last month, New York’s Department of Health and Mental Hygiene, a resource for other people with bed bug infestations, had to fumigate one of its floors.
According to the survey, the majority of pest control operators from Europe, Africa, Australia and North America said bed bugs were the most difficult insect pest to control, more so than ants, termites and even the formidable cockroach. Another study showed that in London alone, bed bug treatments grew by a quarter each year between 2000 and 2006.
The worst aspect about this is that we thought we had tackled the bed bug problem before. Clive Boase, a pest management consultant in Suffolk and author of the London survey, says that UK bedbug numbers began decreasing in the 1930s, thanks to changes in social housing and public health policies, which led to the demolition of old publicly-funded housing and teams of inspectors checking homes for vermin, respectively. New pesticides introduced in the 1940s, including DDT, also helped to bring numbers down, and by the 1950s infestations were rare. The US saw a similar drop in infestations from the late 1940s onwards, thanks to the advent and widespread use of DDT and other chlorinated hydrocarbon pesticides.
So, where is the chemical cure this time around? Or, is there any relief to be found in the myriad bed bug products and services on the market, from growth regulators to heat treatments?
The pesticides currently available, says Dini Miller, an entomologist and bed bug expert from Virginia Tech, are “not practical to use in a widespread way because of the cost.” New, cheaper pesticides are too expensive and time consuming to develop, she adds. Because bed bugs live primarily in the bedroom, chemical companies must provide extensive toxicity data to prove it is safe for indoor use, as it might come into contact with people or pets.
But, proving that a pesticide works and is safe could cost a company up to $256 million over eight to ten years for each active ingredient, according to a 2010 industry study conducted for Crop Life America and the European Crop Protection Association. The investment may not be worth it. The US accounts for over a fifth of the world’s pesticide use, the vast majority of which is used in agriculture, followed by herbicides and then insecticides. Compared to the vast expanse of farmland and orchards, the real estate of all of the apartments and houses in the world combined is small and brings in less money, says Miller. This is especially a problem considering patent protection on a novel ingredient runs out after around 20 years, after which the tech is open to generic competitors.
Even if making a new bed bug insecticide were lucrative, there are other challenges. There is the problem of figuring out how a chemical has to function in order to best kill bed bugs cheaply, efficiently and safely. This requires intimate knowledge of the bed bug’s basic biology. But, because bed bugs were at such low levels for decades, interest in studying them waned. Starting in the early 2000s, once it was clear the resurgence was real and that bed bugs weren’t going anywhere, scientists had to relearn bed bug basics from scratch, starting with fundamental aspects as how to raise them in a lab.
Then there is the problem of paying for the research. While dozens of labs now work on the basic science of bed bugs worldwide, funding remains low in part because bed bugs are not known to spread disease.
Finally, there is the problem of insecticide resistance. Even DDT, the supposed miracle cure, wasn’t immune to this. Five years after the pesticide was in widespread use in the US, DDT-resistant bed bugs popped up in Hawaii; in the 1950s and 1960s, resistant strains were found elsewhere in the US and in Japan, Korea, Iran, Israel and French Guiana, to name a few.
No chemical insecticide is immune to resistance, particularly if it is overused. Today, roughly 90% of bed bugs have a genetic mutation that makes them resistant to pyrethroids, a class of insecticides commonly used for bed bugs that work in a similar way to DDT.
So, chemicals are not the sole answer. Neither, it seems, are any other options when used alone. “There is no silver bullet,” says Michael Potter, an entomologist from the University of Kentucky. Still, chemicals and other tactics can be used in an integrated pest management strategy, where they are sometimes used sparingly along with heat treatments (bed bugs die at 45C), desiccants such as silica gel and diatomaceous earth that fatally dry the bugs out, or vacuuming and getting rid of clutter.
Biological tactics are emerging as another possible option. Insect growth regulators, or IGRs, are chemicals that prevent bed bugs from completing their lifecycle, stunting their growth so they can’t reproduce. But, IGRs are slow-acting, and the bugs will still bite even if they can’t breed. On the horizon, perhaps, are genetically modified versions of symbiotic bacteria that live in the insect’s gut, including Wolbachia, which may be exploited for pest management. Or, the bugs’ pheromones, which tell them where to go and who to mate with, may also be reengineered and used against them.
In the meantime, public awareness measures can keep bed bugs from spreading. Good practices include: checking hotel room beds before unpacking, being mindful of belongings like a coat draped carelessly on an unknown couch, washing clothing in hot water and vacuuming suitcases after travelling, and avoiding discarded furniture on the street. Some experts also recommend sealing mattresses and box springs in encasements specifically intended to keep away bed bugs, which may make the bed easier to treat and could save it from permanent damage.
These combined efforts have knocked down infestations in some areas, says Boase, particularly among high-end hotels and the rich. Both can afford to throw money at the problem. Right now, he adds, the most severe infestations in the UK are in low-income housing – not because poor people are more apt to get them, but because they are less likely to be able to afford the treatments. The US has a similar problem. Better control will depend on cheaper, more efficient options entering the market.
“I feel that it is possible to bring infestation levels down in that residual housing area, but we don’t have the tools of infrastructure to support it,” says Boase. Then again, he says, “we’ve never had [total] eradication before.” But, with cheaper tools, we may be able to knock bed bug levels back down everywhere. Or at least, he adds, “we love to think we can.”
* Many people write “bedbugs”, but entomologists use two words when describing Cimex lectularius, because it is a “true bug” (Hemiptera). Entomologists always use two words for insects that are true to the common name they have – so for example, house fly is two words because those are actually flies, but butterfly is one word because they aren’t flies.