Bedbugs: how research is honing its weapons to get rid of them

Cimex lectularius takes advantage of its resistance to spread. Human beings have probably always coexisted with bedbugs, found in ancient Egyptian tombs. But after having seemed to disappear, they come back in force, and prove to be resistant to insecticides. According to those infected, it has become difficult to get rid of them. How can we explain their resistance, and do effective techniques exist to fight against the invasion, without resorting to insecticides? In the late 1930s, the use of insecticides such as DDT almost wiped out the insect, so much so that by the end of the 1950s there were virtually no bedbugs left, at least in the developed nations. Parasitologist at the Avicenne hospital in Bobigny, Dr Arezki Izri explains that “in a parasitology department, in the 1990s we observed a patient bitten every year or every 2 years. It was in 2010 that cases increased sharply.” How to explain this resurgence?

For Dr Izri, “two main reasons explain this increase, resistance to insecticides and travel”. In the 1950s, most bed bugs were sensitive to insecticides, but through exposure, some acquired resistance genes. Chemical treatments therefore favored these resistant bedbugs, which reproduced more than the bedbugs which remained sensitive to them. Current bedbugs, of which “up to 90 to 92% are resistant to all insecticides,” says Dr. Izri, are probably descendants of selected resistant bedbugs. Because of this resistance, the irrational use of insecticides now tends to spread the bedbugs. “Insecticides irritate bedbugs, but do not kill them,” explains Dr. Izri. They then act as repellents and cause the dispersion, therefore the spread of bedbugs. They worsen the situation, not to mention that these products are toxic to humans and biodiversity. » The parasitologist thus criticizes the 2022 interministerial plan to combat bedbug infestations, considering that it “did not benefit from scientific advice, it was signed with the pest control companies”.

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Bedbugs are in an “arms race against chemical control,” underlines natural history museum researcher Romain Garrouste, a bedbug specialist. “It is important to acquire biological knowledge to apply it in control strategies. » Indeed, the museum holds collections of bedbugs that are at least fifty years old, and the genome of the insects could be analyzed. These studies would make it possible to study the mechanisms of acquisition of resistance to insecticides, as has been done for mosquitoes. To make matters worse, the bad reputation of bedbugs does not encourage owners and real estate agencies to communicate about an infestation, which contributes to the spread. Romain Garrouste testifies to “bad practices of owners who do not want to say when they have bedbugs, because they are afraid of a bad reputation, while the contamination process is random”.

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Faced with insecticide resistance and the complexity of extermination, are there effective means of control to disinect an entire home? A team of which Dr Izri is part published this year, in the International Journal of Environmental Health Research, a study showing that all bedbugs exposed directly to 50°C for 60 minutes were eliminated. On the other hand, it takes 60 minutes at 60°C to remove 100% of those covered by a fabric, hidden in furniture, or protected by a mattress. And 120 minutes at 60°C to kill 100% of bedbugs protected in a double layer of coverage. This study was partly funded by the ARS Ile de France and the city of Paris. But since 2008, Dr Izri has highlighted a lack of investment in detection and physical control research, despite requests from researchers. So Dr Izri wants to be able to finance the creation of future machines capable of heating residential rooms to 60°C for two hours. Another avenue under study is inspired by biomimicry, “a solution inherited from the observation of nature,” explains Romain Garrouste. For example, carnivorous plants and bedbugs emit volatile compounds to attract insects, which could be used to trap the intruder. » Research is underway to isolate and manufacture these volatile compounds, such as pheromones, which could attract bedbugs into effective traps. For Romain Garrouste, research must be directed to “find a combination of methods without chemical impact on people who live in the treated areas and without it being complicated for them.” The subject is scientific, social and psychological at the same time. He calls for the creation of a “task force” on bedbugs, imagining a grouping of several research laboratories with varied skills. “Researchers are capable of knowing what is important, but we don’t trust them,” regrets the researcher.