AsianScientist (July 19, 2017) – It is possible to identify the individual bitten by a mosquito based on DNA recovered from human blood in the belly of the mosquito, even two days after the person was bitten. These findings, by a team of forensic scientists at Nagoya University, have been published in PLOS ONE.
Blood from a mosquito’s last meal contains human DNA that can be matched to the person who was bitten. This could prove useful in helping the police identify individuals at a crime scene and may one day be used to convict offenders. But questions remain about how long it takes for a mosquito to digest human blood until the human DNA becomes unrecognizable.
In this study, researchers used the polymerase chain reaction, or PCR, to amplify short tandem repeats of human DNA found in the stomach of mosquitoes. The team then used the amplified samples to find out how much DNA is left after the mosquito feeds and who the DNA belongs to.
“We asked several volunteers to let mosquitoes bite them,” explained forensic scientist Yuuji Hiroshige. “After allowing the mosquitoes to digest the blood for a certain amount of time, we extracted the human DNA and used PCR techniques to amplify the sample for quantification and genotyping.”
By examining DNA in blood digested by two different species of mosquito over a range of times after feeding, the team was able to trace back blood samples to individual volunteers, even after the blood had been digested for two days in the gut of the mosquito. However, after more than three days, the DNA became unrecognizable.
“Ours is the first study to systematically apply modern DNA profiling techniques to the challenging forensic analysis of mosquito blood meal,” said group leader Dr. Toshimichi Yamamoto. “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.”
The article can be found at: Hiroshige et al. (2017) A Human Genotyping Trial to Estimate the Post-feeding Time from Mosquito Blood Meals.
Source: Nagoya University; Photo: Toshimichi Yamamoto.
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