by Under bright lab lights, a research assistant reaches out his forearm and carefully twists a mesh-lidded container onto his skin, allowing a squirming mass of bed bugs to feed on his blood—all in the name of science.
The blood-sucking insects, long hated as itchy household pests, have revealed an even darker, more intriguing potential as Malaysian scientists discovered they can be turned into unlikely crime-fighting allies.
A team from the Science University of Malaysia (USM) in northern Penang has found that tropical bed bugs can retain human prey’s DNA for up to 45 days after eating an unwary victim.
This makes the tiny animals, which like to lurk in cracks in headboards, mattress seams and pillowcases, ideal evidence when it comes to locating suspects at crime scenes.
Police investigators might one day be able to piece together a perpetrator’s full profile from a drop of blood if the animals are present at the crime scene.
Analysis of the insects can provide information about gender, eye color, hair and skin color, entomologist Abdul Hafiz Ab Majid told AFP.
“We call bed bugs ‘Musuh dalam selimut’ (Malay for ‘the enemy in the ceiling’),” Hafiz said, adding that “they can also be spies” to help solve crimes.
– DNA profiling –
In a lab deep in USM’s School of Biological Sciences, Hafiz and postdoctoral researcher Lim Li have spent nearly half a decade studying tropical bed bugs.
The bloodsuckers, scientific name Cimex hemipterus, are the most common species in Malaysia and the tropics.
The beetles are raised in containers under a lab bench, each wrapped in black plastic to mimic the conditions in which the insects thrive.
“We put folded pieces of paper in the small containers so the bed bugs have something to climb on,” Hafiz said.
Because the laboratory temperature is kept constant at 23 to 24 °C, the insects suck up 1.5 to 5.3 microliters of blood with each feeding, “a lot less than a droplet,” Hafiz explained.
Researchers found that DNA extracted from bed bugs that had fed on human blood could restore basic “phenotypic profiling,” a person’s observable characteristics, and gender for up to 45 days.
Using so-called STR (Short Tandem Repeat) and SNP (Single Nucleotide Polymorphism) markers, specific DNA sequences extracted from blood, researchers can determine the gender, eye color, hair and skin color of potential suspects long after they have fled the scene.
The USM study, titled “Human Profiling from STR and SNP Analysis of Tropical Bed Bug, Cimex Hemipterus,” was published two years ago in Nature’s Scientific Reports.
It was the first documented forensic use of tropical bed bugs.
– “Perfect” forensic tool –
Unlike mosquitoes and flies, bed bugs can’t fly, and once they’ve fed, “they get stuffed and can’t move around as much,” Hafiz said, adding that they can only move within 20 feet (six meters) of where they fed.
“This makes them unique. We can say that they are perfect as a forensic tool compared to flyaway mosquitoes,” Hafiz added.
The beetles are particularly useful at crime scenes where liquids are wiped away to destroy evidence, as the animals are often well hidden.
Back in the lab, researcher Lim didn’t hesitate to demonstrate a feeding session and even joked that she had been a “willing victim” for science.
“I let them feed on my blood when I wanted to test how long it would take for human DNA to degrade,” she said.
Lim insisted the inconspicuous beetles are “misunderstood creatures” and do not spread disease – although their bite leaves an itchy rash that can last for weeks.
“Maybe we can try to educate people because bed bugs aren’t actually vectors, so even if you get bitten, they can’t transmit disease to you,” she said.
While researchers envisioned a future in which tiny bed bugs at crime scenes could trick investigators into murdering suspects, Hafiz said the insects weren’t a magical solution.
Bed bugs have their limitations — especially when it comes to solving cold cases, Hafiz said.
“It only gives investigators a 45-day time frame to use bed bugs as evidence – and only if they are available at the crime scene,” he said.
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