Wednesday, November 5, 2014

Snake bites

Bites from venomous snakes are common in many parts of the world and an especially serious unresolved health problem to millions of people living in South and Southeast Asia, as well as Africa and Latin America. Although there are no reliable numbers at the global scale, it has been estimated that at least 421,000 cases of venom snakebites with up to 94,000 deaths occur worldwide each year. However, experts warn that these figures may underestimate the real problem, which is believed to affect several million people bitten by venomous snakes annually and hundreds of thousands who die or survive disabled, suffering from amputation or deformed limbs as a result of unavailable or delayed treatment.

People bitten by snakes often do not seek treatment at a medical facility, and if they do, the vast majority don't take the snake with them although it is often killed. Of course they also can't identify the species that actually bit them. However, knowing the species of snake is critical to determining the best course of treatment. And even if the victims do everything right, the clinical personal does not necessarily has the expertise to identify the snake species.

At the current annual meeting of the American Society of Tropical Medicine and Hygiene in New Orleans a team of scientists from Nepal, Germany and Switzerland present a clinical study on the DNA-based species identification of snakes responsible for venomous bites in rural Nepal (Abstract #692, page 209).

Starting with a simple DNA swab taken from fang marks on people bitten by snakes, an international research team correctly identified the species of the biting snake 100 percent of the time in a first-of-its-kind clinical study.

This study used a combination of  morphological and molecular approaches (PCR-aided DNA sequencing from swabs of bite sites) to determine the relative contribution of  venomous and non-venomous species to the snakebite burden in southern Nepal. 

A 100% recovery rate is very impressive and shows the power of modern DNA-based ID systems. Based on these early results the research team is currently developing a rapid diagnostic "dip-stick" test that could be used to rule out certain common venomous snakes and help physicians more quickly to decide on the best course of treatment. Conversely, if for example, krait (Bungarus sp.) venom is detected, doctors could quickly give anti-venom instead of waiting for clinical signs poisoning, as is current practice. They would also accelerate the transfer of patients to referral hospitals with intensive care units able to ensure adequate respiratory support. Such a test would be easy to administer in rural healthcare settings with limited resources.

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