A new weapon in the fight against crime has been uncovered by a Japanese team of forensic scientists.
Researchers have discovered that DNA found in blood sucked out of a human by a mosquito can be identified up to two days later.
The finding could enable investigators to use this new form of evidence to solve murders and other serious crimes.
Researchers at Nagoya University in Japan have discovered that DNA found in blood sucked out of a human by a mosquito can be identified up to two days later. Scientists asked seven volunteers to let mosquitoes bite them. They then allowed the mosquitoes to digest the blood for varying lengths of time.Using a technique called polymerase chain reaction (PCR) they then examined the results.They found that 48 hours was the maximum length of time after which this was possible.After three days, the blood completely broke down. The finding could one day enable investigators to use this new form of evidence to solve murders and other serious crimes.
Researchers at Nagoya University in Japan made the discovery after asking seven volunteers to let mosquitoes bite them.
Until now, it had not been known how long human blood drawn by the creatures would retain an identifiable DNA profile.
The team allowed the mosquitoes to digest the blood for varying lengths of time, before attempting to extract the human DNA.
Using a technique called polymerase chain reaction (PCR), a standard tool in forensics for amplifying a tiny DNA fragment up to thousands of times, they then examined the results.
‘Ours is the first study to systematically apply modern DNA profiling techniques to the challenging forensic analysis of mosquito blood meal’, said lead scientist Toshimichi Yamamoto in a written statement.
‘We hope this will help crime scene investigators collect reliable evidence that could be used to guide investigations and support convictions.
‘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.
‘In the future, it might provide evidence that can be used to convict offenders.’
The researchers found that they could accurately match the minuscule blood traces to the volunteers who had offered themselves up as a meal, even after two days of digestion in a mosquito’s stomach.
But they found that 48 hours was the maximum length of time after which this was possible.
After three days, the blood completely broke down.
The experiments were performed with two species, Culex pipiens pallens and Aedes albopictus, both found throughout much of the tropical and sub-tropical world.
Most mosquitoes do not travel beyond a radius of a few hundred metres.
Depending on the species, they have lifespans ranging from a few days to a couple months.
Females, the ones that bite, generally live far longer than males.
The full findings of the study were published in the journal PLOS One.
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