Calling into Question the Use of the “Big 4” for Snakebites in India

Newswise — For decades, the concept of the "Big 4" Snakes of Medical Importance has reflected the view that four species are responsible for Indian snakebite mortality. The recent recognition of a snake in India, previously considered harmless, as a species capable of causing life-threatening envenoming brings the value of the "Big 4" into question. A new study reviews the "Big 4" and is published in the latest issue of Wilderness and Environmental Medicine.

The World Health Organization (WHO) estimates that the annual mortality due to snakebite in India is approximately 50,000. Many factors contribute to this mortality rate in which there are also many questions related to the treatment of snakebite victims. A study in Kerala, India, established that out of 44 snakes killed and brought to two hospitals by snakebite victims from 2000 to 2004, nine were the hump-nosed pit viper. All nine were misidentified, however, by the treating physicians.

The recognition of new species of medical importance also has great significance in the field of snake antivenom design and manufacture. The current Indian snake antivenoms, produced by seven manufacturers, have remained unchanged for many decades. The antivenom producers have argued that their products cover all snakes of medical significance as defined by the "Big 4." It's been impossible, to date, to convince them to produce new antivenoms against the emerging species, the study said.

Treating the "Big 4" as a single and fixed entity by both the antivenom manufacturers and medical professionals is, therefore, giving rise to numerous erroneous assumptions that are negatively impacting patient care. Study researchers Ian Simpson and Robert Norris advocate the use of the WHO methodology for identifying snakes of medical significance:

-Class I—Commonly cause death or serious disability-Class II—Uncommonly cause bites but are recorded to cause serious effects (death or local necrosis)-Class III—Commonly cause bites but serious effects are very uncommon The WHO criteria for listing snakes of medical importance is a much more practical tool, the researchers said, as they allow for the possibility that other snakes may yet emerge as also being medically important.

"If there are species that are currently regarded as harmless, yet are causing morbidity and mortality, it is essential that this be established and that effective antivenoms are developed in order to reduce morbidity and save lives," said the study's researchers.

To read the entire study, click here: http://www.allenpress.com/pdf/weme_18_119_2_9.pdf

Wilderness and Environmental Medicine is a peer-reviewed quarterly medical journal published by the Wilderness Medical Society. For more information, visit http://www.wms.org.