New Hotspot Maps Show Global Snakebite Vulnerability

New Hotspot Maps Show Global Snakebite Vulnerability
Photo Credit: Wikipedia Commons
What you need to know

Up to 92 million people are vulnerable to potentially fatal venomous snakebites, many in Southeast Asia and sub-Saharan countries.

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When thinking of global health problems, snakebites may not immediately come to mind. According to the World Health Organization (WHO), an estimated 2.7 million people are poisoned each year by venomous snakes, with fatalities ranging from around 81,000 to 138,000, and triple that suffering amputations or other permanent disability.

From the tropics to deserts, snakebite is a worldwide health concern, where availability and access to antivenom means life or death for vulnerable populations, including those in Taiwan living near bamboo pit viper, Chinese moccasin, and other commonly found poisonous snakes.

In a study recently published in The Lancet, and funded by the Bill & Melinda Gates Foundation, scientists produced maps of global snakebite hotspots. The study combines ranges of 278 snake species, availability and quality of health care, proximity to population centers, and snakebite and antivenom data, to map populations most at risk of snakebite. The results identify further data needed to help manage the global snakebite problem.

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Average travel time to nearest major city for populations living within snake ranges. The Lancet. CC BY 4.0

The hotspot maps are the first of their kind at a global level. According to the study, existing research focused on snakebite risk at national levels and did not include all medically important venomous snake species -- meaning, snakes identified by the WHO as venomous, widespread, and causing morbidity, disability, or mortality.

Local or national maps don’t adequately characterize snakebite risk globally, and due to inadequate estimates, possibly interfere with production and distribution of antivenom supplies to populations at risk.

Snakebite data for Taiwan is limited and often underestimated -- characteristics shared by global snakebite metrics.

The new global snakebite hotspot risk maps are the beginnings of synthesizing worldwide snake distributions with public health capabilities to identify populations most vulnerable to snakebite.

Hotspots as defined by the study are “people living in areas within the range of one or more medically important venomous snake species, and more than three hours away from major urban centers with Healthcare Access and Quality (HAQ) Index deciles of 1–3.”

The HAQ Index uses 32 causes of death -- such as tuberculosis, vaccine-preventable diseases, respiratory infections, etc.-- that should not occur when effective care is available. Each country has a HAQ Index based on a scale of 0-100, with zero the worst. Taiwan, for example, is in the ninth decile, meaning it’s in the 90th percentile, while the Central African Republic, for example, is in decile one.

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Aggregated second administrative level vulnerability to all species of medically important venomous snakes, as measured by the absolute number of people. The Lancet. CC BY 4.0

Despite having 15,775 people within range of medically important snakes, Taiwan is not a hotspot per the study criteria due to its vulnerable populations existing within three hours of major urban areas with a high HAQ Index.

For comparison, Ethiopia has a HAQ Index of one, with a vulnerable population count of 17,543,888. Indonesia, at HAQ Index three, has 14,827,781 vulnerable people.

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Expert opinion range (EOR) for Trimeresurus stejnegeri, commonly known as bamboo pit viper. The Lancet. CC BY 4.0

Independent of travel times, HAQ Index, and access to antivenom, Taiwan is still within the range of medically important snakes. In addition, snakebite data for Taiwan is limited and often underestimated -- characteristics shared by global snakebite metrics. According to a study published in the Journal of Acute Medicine, from 2005 to 2009, 4,647 snakebites were reported in Taiwan and included two documented deaths.

By identifying global populations vulnerable to snakebite, the new hotspot maps make progress toward guiding future research and treatment, prioritizing data collection, and deploying snakebite interventions.

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Editor: David Green