Picture this: You’re a detective working on a murder. The scene is an empty hotel room with a dead body and not much else. There are no fingerprints, no footprints, no apparent traces of the culprit, no witnesses, no weapon. But then you have a eureka moment: That mosquito buzzing near your ear could be flying around with a sample of DNA.
Researchers from Nagoya University in Japan have demonstrated how human blood extracted from a mosquito's stomach could be used for DNA analysis up to 48 hours after it sucked blood. That means, in theory, a mosquito could be used by forensic scientists to profile a person at a crime scene. Of course, depending on the circumstances, this won't always catch the culprit as the mosquito could harbor the blood of a different nearby individual.
The study was published in the journal PLOS One.
In an experiment, they asked several volunteers to let mosquitos bite them. They then extracted the human DNA from the mosquito and used a polymerase chain reaction, or PCR, to multiply the single DNA fragment in order to amplify the size of the sample. By examining this DNA, they were able to successfully identify the individual volunteers. Their research examined DNA in the blood digested by two different species of mosquito over a range of times after feeding.
Their study demonstrated this in the Culex pipiens pallens and Aedes albopictus, two mosquito species found throughout the tropical and subtropical world. Unfortunately, time is of the essence. The researchers were able to do it up to 48 hours after the mosquito bit the volunteers. However, by day three, the mosquito had completely broken down the blood and digested it.
With a little more fine-tuning, the researchers hope to make the time estimate more accurate.
“Ours is the first study to systematically apply modern DNA profiling techniques to the challenging forensic analysis of mosquito blood meal,” research leader Toshimichi Yamamoto said in a statement. “We hope this will help crime scene investigators collect reliable evidence that could be used to guide investigations and support convictions. Although we need to take some steps to improve our methods and obtain more data, with more accurate quantification methods, we might be able to estimate the time after mosquitoes' blood feeding with even greater accuracy."
