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[1] Under glaring laboratory lights, a research assistant extends his forearm and carefully inverts a mesh-topped container onto his skin to allow a wriggling mass of bed bugs to feed on his blood, all in the name of science. Long-loathed as itchy household pests, the bloodsucking insects may have darker, more intriguing potential, as Malaysian scientists have discovered they can be turned into unlikely crime-busting allies.
[2] A team from Universiti Sains Malaysia (USM), or the University of Science Malaysia, in the country’s north found that tropical bed bugs can retain DNA from human prey for up to 45 days after feeding on an unwary victim. This makes the tiny critters, who love to lurk in headboard cracks, mattress seams and pillow covers, ideal sources of evidence for pinpointing suspects at crime scenes.
[3] From a speck of blood, police investigators may one day be able to piece together the full profile of an offender, if the critters are present at a crime scene. Analysing the insects could reveal a person’s sex, eye colour, hair and skin colour, entomologist Abdul Hafiz Ab Majid told Agence France-Presse.
[4] In a laboratory tucked deep inside 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 found in Malaysia and the tropics. The bugs are reared in containers under a laboratory bench, each wrapped in black plastic to mimic the conditions the insects thrive in.
[5] With the lab’s temperature kept at a constant 23 to 24 degrees Celsius, the insects suck up 1.5 to 5.3 microlitres of blood at each feeding, an “amount less than a droplet”, Hafiz explained. Researchers found that DNA extracted from bed bugs that had fed on humans could recover basic phenotypic profiling – a person’s observable traits – for up to 45 days.
[6] Using STR (Short Tandem Repeat) and SNP (Single Nucleotide Polymorphism) markers, specific DNA sequences extracted from the blood, researchers can determine the sex of potential suspects, as well as their eye, hair and skin colour, long after they have fled the scene. The USM study “Human profiling from STR and SNP analysis of tropical bed bug, Cimex hemipterus” was published in Nature’s Scientific Reports.
[7] It was the first documented forensic use of tropical bed bugs. Unlike mosquitoes and flies, bed bugs cannot fly. Once they have fed, they “become engorged and can’t move around that much”, Hafiz said, adding that they could only move within six metres of where they had been fed. The bugs are particularly useful at crime scenes, where fluids have been wiped away to destroy evidence, because they are often well hidden.
[8] Researchers imagine a future where tiny bed bugs at crime scenes could lead investigators to murder suspects, but Hafiz said the insects were no magic fix. They have their limits, especially when it came to cracking cold cases, he explained. “It only gives investigators a time frame of 45 days to use bed bugs as evidence – and only if they are available at the crime scene,” he said.
Source: Agence France-Presse, November 25
