World’s Deadliest Neglected Disease: Snakebite Slithers Under the Radar

The world’s deadliest “neglected tropical disease” isn’t infectious, it’s venomous.

In 2019, about 65,000 people are estimated to have died from snakebites, with 81% of these deaths occurring in India, where snakebite is estimated to cause more severe health problems than HIV, breast cancer, or even malaria. Snakebite sequelae vary, depending on whether the bite is from a neurotoxic snake or a hemotoxic snake, with each causing distinct short-term and long-term effects.

While snakebite has laid low, it hasn’t been able to entirely avoid the spotlight. The World Health Organization declared snakebite a Category A neglected tropical disease in 2017, and it received the documentary treatment with “Minutes to Die.”

Nicholas Roberts, MPH, of the Institute for Health Metrics and Evaluation (IHME) in Seattle, presented modeling estimates on snakebite at the 2020 American Society of Tropical Medicine & Hygiene virtual meeting, including data from IHME’s Global Burden of Disease study.

Though it may not be nearly as well-known as IHME’s COVID-19 modeling, the Global Burden of Disease study was an equally massive undertaking: quantifying disease burden from 359 causes of disease and injury, and 87 risk factors, in 204 countries and territories from 1990-2019 by age and sex.

And in 2019, Roberts reported that snakebite was estimated to result in 65,000 deaths and 3 million years of life lost. Researchers then focused their attention on India, as 80.5% of deaths occurred there.

They zeroed in on the “big four” Indian snakes, which are estimated to account for 90% of deaths in India: cobra, krait, Russell’s viper, and saw-scaled viper.

While all these snakes can cause death or serious injury, they do so in different ways. Cobras and kraits are neurotoxic snakes, while both vipers are hemotoxic snakes. And based on a systematic review of epidemiological literature in India, neurotoxic snakes had about double the case-fatality rate of hemotoxic snakes (8.8% vs 4.2%, respectively).

Symptoms of each snakebite were different, with blood clotting disorders estimated to occur in 40%-90% of hemotoxic snake bites, while neurotoxic snake bites were more likely to cause respiratory failure, paralysis, and vision problems, Roberts said.

In India, 3.0 million disability-adjusted life years can be attributed to snakebite, though that number has decreased over time since 1990. Roberts noted snakebite ranks fourth among injuries in India, behind road injuries, self-harm, and falls.

Even if you survive a snakebite, it can have long-term health effects, such as chronic kidney disease (CKD), skin necrosis, and amputation. Not surprisingly, amputation caused the greatest number of years lived with disability.

But of the estimated proportion of acute kidney injury caused by snakebite, Roberts said while most get better, 15% go on to stage 4 CKD.

Frustratingly, much of the long-term sequelae of snakebite are preventable, as anti-venom exists for all the “big four” snakes, he added.

“If [anti-venom] was more accessible, those deaths and severe outcomes could be prevented,” Roberts said.