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Bed bugs and their eggs. They live and reproduce in hidden areas, such as, under the straps of an unused bag. Photo: Ventriloquist

Bed bugs continue their comeback worldwide – and forensic science just may have found a useful, if abhorrent, crime-solving partner.

The bloodsuckers scuttling in the shadows of bedrooms and apartments and dwellings across the world could be a huge forensic trove of full autosomal DNA profile of the humans on which they feed, according to a new study in the journal Forensic Science International.

“These results reveal that identification of multiple human hosts is possible from a single bed bug,” write the authors. “Hence, bed bugs can serve as physical evidence in temporal and spatial predictions to match suspects and/or victims to specific locations in criminal investigations.”

The team took the bed bugs (Cimex lectularius), separated into three containers. One was fed female human blood, one male human blood, and the third mixed male and female blood.

The engorged male bedbugs were collected and placed into Eppendorf tubes, which were then filled with ethanol at 12-hour spaced intervals, according to the study.

The ethanol was removed, the bed bug was cleaned, and then universal buffer was added, and a clean probe “vigorously homogenized” the critter.

The resulting fluid was blotted and an FTA blood card was then left to dry. The DNA was amplified, quantified and processed on the AmpFlSTR Identifiler, Quantifiler Duo Kit, and the ABI 7500 Real-Time PCR System, all Thermo Fisher Scientific products.

The bed bugs generally feasted on three to four microliters of human blood – a total which dropped to one to two microliters 60 hours after the meal.

“Interestingly, the average total human DNA recovered from a bed bug fed on human female blood is 3.4 to 5.5 times higher than human DNA recovered from bed bugs fed on human male and pooled blood,” according to the paper’s findings.

Accordingly, complete autosomal STR profiles of females were sequenced at 96 hours. The male and mixed blood samples were completely concordant up to 72 hours, conversely.

“This study demonstrates for the first time that the use of forensic biology and entomology methods enable identification of human blood sources from bed bugs,” the results state. “It is also evident that single-source as well as multiple human hosts can be positively genotyped up to 72 hours (post-blood meal).

“We recommend that crime scene technicians collect multiple blood fed bed bugs form the crime scene to maximize the recovery of human blood and human-specific DNA and increase the chances of generating complete DNA profiles from bed bugs,” they add.

Previous research has, of course, shown that mitochondrial DNA can be extracted and typed from blood feeding insects like crab louses and blue bottle fly maggots. Nuclear DNA research on the blood meals of mosquitoes, lice and maggots have also been conducted.

But bed bugs cannot fly – and stay especially close to their host. The latest study is the first of its kind with full STR profiles, and which could have huge forensic implications in the right kinds of cases, write the scientists, from North Carolina State University and Fayetteville State University.

“Although a small fraction of a bed bug population can walk relatively long distance, most remain near the host,” write the scientists. “This makes bed bugs useful for validating the location of a suspect or a victim in legal and/or forensic investigations.”

Bed bugs are making their resurgence, in large part, due to the discontinued use of the pesticide DDT over the last several decades. It was the use of that poison which had effectively eradicated them in some parts of the world after World War II.

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