New Delhi, Nov. 4: Scientists today announced a prototype forensic test that uses a single swab from fang marks of snakebites to identify the species of the snake and help bite victims receive appropriate anti-venom and treatment.
The new diagnostic tool ,aimed at quickly classifying bites as venomous or non-venomous, has emerged from a collaborative research effort between a doctor in Nepal and two scientists in Germany and Switzerland who share interests in snakebites.
Bites from venomous snakes are common in rural areas across South Asia, Southeast Asia, Africa and Latin America. A study published in the journal PLOS Neglected Diseases three years ago had estimated that about 46,000 people die from snakebites every year in India.
Public health experts believe most of these deaths occur primarily because the bite victims are unable to reach medical facilities in time or receive inappropriate treatment because the species of the snake remains unidentified and doctors have to treat them blindly.
“We just have to know which snake bit the victim to start the correct therapy,” Sanjib Sharma, an internal medicine specialist and research team member at the BP Koirala Institute of Health Sciences, Nepal, told The Telegraph.
The new test uses a swab stick to collect genetic material, or DNA, from the site of the fang marks made by the snakebite. The scientists expect that when a snake bites a person, it also transfers a bit of its own DNA to the victim — either cells, cellular debris, or its saliva.
“We always pick up lots of human DNA from the bite site, but we also hope to get traces of snake DNA,” Ulrich Kuch, the head of the department of tropical medicine and public health at the Health Sciences Centre, Goethe University, told this newspaper.
The test seeks to amplify the snake DNA, if present, and thus identify the species. A study of the test in Nepal found that among 194 DNA samples collected from bite sites, 42 were from the spectacled cobra and 22 from the common krait.
“This DNA test may hasten more effective bedside diagnostics for snakebite victims, giving them a better chance of survival and making a full recovery,” said Francois Chappuis, chief of the division of tropical medicine at Geneva University Hospitals, Switzerland, who led the study and presented the results today at the annual meeting of the American Society of Tropical Medicine and Hygiene.
The researchers plan to begin field trials of the diagnostic test in Nepal and Myanmar in March 2015. “This test will also be valuable to India and we are exploring the possibility of collaborating with Indian researchers for trials there,” Sharma said.
The effects of venom on the human body depends on the species as well as the amount of venom that the snake has injected into the victim. Bites from cobras and kraits, for instance, lead to different sets of complications. Patients may show up with similar symptoms such as nausea, headache, drowsiness and respiratory paralysis but, Sharma said, the treatment methodology would depend on the identity of the snake.
Although most snakebites are from non-venomous snakes, bite victims are typically kept in hospitals for at least 24 hours of observation when the identify of the snake species that bit them is unknown. The diagnostic test, if it is able to rule out a venomous snake, could avoid unnecessary observations.
The scientists caution that the diagnostic tool will not work if the amount of snake DNA at the bite site is too low. “Washing the site of the bite or applying traditional remedies like plant extracts may reduce the chances of recovering snake DNA,” Kuch said.
In the clinical study in Nepal, snake DNA could be extracted from only one in four bite wounds. In 21 cases, patients or those accompanying them brought the dead snake that had bitten them and the test provided independent confirmation of the species in each case.
