Snakebite test correctly IDs attackers in Nepal

DNA from swab of bite site can diagnose serpentine culprit


ONCE BITTEN  Forensic tests of bite marks might reveal the guilty snake species — such as this cobra — in cases where patients aren't sure what attacked them, offering a bit of clarity that can speed treatment.

H. Krisp/Wikimedia Commons (CC BY 3.0)

NEW ORLEANS — Swabbing for traces of snake DNA around bite marks on people can reveal the guilty serpent, a use of forensics that could change how people in regions beset by snakebites identify the culprits, a study in Nepal finds.

Snake identification can be lifesaving if it guides use of antivenom accurately, said François Chappuis, a tropical medicine doctor at Geneva University Hospital, who reported the findings November 4 at a meeting of the American Society of Tropical Medicine and Hygiene. But the current snake identification method in South Asia relies on patients’ recall or symptoms, he says.

His team used polymerase chain reaction to amplify and identify DNA from snake fluids left near bite marks in 194 patients. Armed with this forensic evidence, the researchers found that 87 of the snakes that had bitten people were venomous, including 42 cobras (Naja naja) and 22 common kraits (Bungarus caeruleus).

With 21 people who had arrived at clinics with the venomous snake that had bitten them, the scientists were able to double-check their work and found that their test correctly identified every snake. Researchers conducted each DNA test before seeing the snake.

Chappuis said the value of PCR might show up in future tests that would be more practical in the field. His team is planning to test diagnostics that use blood samples from victims to reveal the snake species — within 20 minutes in a best-case scenario. PCR would validate those results. 

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