These Maps Show How Millions of People Are Vulnerable to Deadly Snakebites

"Snakebites are a global problem."

Flickr / Rushen!

For most people in the United States, venomous snakes rank pretty low on the list of things to worry about on a daily basis. But for millions of people around the world, especially those who live in tropical regions and in communities that are a long way away from cities, dying or becoming permanently disabled as a result of a venomous snake bite is a disturbingly real possibility. Nearly 93 million people worldwide are at high risk of dying from snake envenomation, according to a new study by an international team of tropical disease and public health experts. It’s an issue one of the study’s authors tells Inverse is “a global problem.”

The finding, presented in a paper published Thursday in the medical journal The Lancet, is based on global data that analyze how many people live near highly venomous snake habitats, how close these people live to adequate medical care, and whether there’s even an appropriate antivenom for the snakes that live near them. Based on the overlap of these three factors, the data revealed that Southeast Asia, the Congo Basin in Africa, and the Amazon Basin in South America are the regions in which people are at the highest risk.

The study's authors compiled data on the range of venomous snakes (A) and the snakes for which there is no appropriate antivenom (B).

Longbottom et al

To calculate the hazard of snake bites, the researchers used a model that’s typically used to examine neglected tropical diseases, which reflects a shift in the public health community’s thinking about venomous snakes. In June 2017, out of concern for the risk posed to the world’s most vulnerable communities, the World Health Organization classified snakebite envenomation as a Neglected Tropical Disease. This category includes the mammal-borne rabies virus and the insect-borne Chagas disease, as well as rarer diseases like leprosy.

This classification opened the door for governments and non-governmental organizations to direct money toward research and treatment efforts to help people who live with a higher risk of snakebites. It also motivated the study’s authors to highlight the current state of the global burden imposed by venomous snakebites.

“Unlike some of the other [neglected tropical diseases], snakebites are a global problem (many NTDs are, as the name suggests, truly tropical, or restricted to a continent),” David Pigott, D.Phil., an assistant professor of global health at the University of Washington and one of the study’s authors, tells Inverse. He notes that, despite the attention snakebites receive in places like Australia, treatment options there are sophisticated and readily available. But when we look at the places that bear the greatest public health burden, a clear picture of inequality emerges.

This map shows how far people living near venomous snakes have to travel to reach the nearest city, a factor that can be critical when seeking urgent medical care.

Longbottom et al

“There are many regions of the world where a concerted, coordinated, well-resourced effort to control the condition is lacking,” says Pigott. “The aim of these maps is to highlight these vulnerabilities — where are there snakes that could be harmful, and where do we most lack the resources to deal with them.” For this reason, Pigott and his co-authors included data on how long it takes people who live near snakes to reach the nearest city for medical care, as well as data on how well that medical care is distributed.

Despite the large quantities of data available on snakes’ ranges, healthcare access, and antivenom availability, other numbers are harder to nail down.

“They don’t have a figure showing actual mortality from snakebites,” Sam Sweet, Ph.D., a professor of ecology and evolution at the University of California, Santa Barbara who was not involved in the study, tells Inverse. This number could be helpful in better understanding the actual mortality risk posed by venomous snakes, but Pigott points out that much of this data is simply not available, highlighting the need for further, more granular study.

“While high-income countries have good reporting of snakebites (many high-income countries have vital registration that can pretty reliably document how many people die due to snake bites for instance), for many countries this is not the case,” he says. This is especially true for the areas of greatest risk identified in the study, which are disproportionately rural.

And since venoms can act quickly and degrade muscle and skin while a patient is awaiting treatment, even nonfatal bites can leave people permanently disabled. As the adage goes: Time is tissue. And numbers for these nonfatal cases are even less well-documented.

There is no antivenom available for the blue Malayan coral snake (Calliophis bivirgatus), a native of Southeast Asia. It's just one of the 118 such snakes around the world.

Wikimedia / LinasD

In addition to healthcare access, though, there are some major medical hurdles to conquer when it comes to treating snake bites. One of those, as measured in the second map in this article, is the availability of antivenoms to reverse snakebite envenomation. Out of 278 venomous snakes identified by the WHO, the study’s authors point out that antivenoms are only available for 119 of them.

“The quality of antivenoms and the availability of antivenoms is very spotty around the world. In some of the places where people are most at risk, antivenom is either not available or of questionable quality,” Steve Mackessy, Ph.D., a professor of biological sciences at the University of Northern Colorado who was not involved in the new study but who extensively studies venomous snakes, tells Inverse.

“Most people think of venoms as a poison, and they’re not. They’re very complex mixtures of a variety of complex compounds,” he says. For this reason, there’s very little crossover between antivenoms that can be used for different snakes. Sometimes different regional populations of the same species will even have different proteins in their venom, making an antivenom effective on certain snakebites in one area but ineffective elsewhere. Mackessy also points out that since antivenoms are biological products, they must be kept at facilities where the staff is trained to properly care for them and administer them, yet another obstacle to increasing the equitable distribution of healthcare for snakebites.

Pigott hopes that as a result of this study, NGOs and governments will hone in on the people who are most in need of greater access to improved antivenoms and the corresponding medical care.

“Because it’s in The Lancet, it’s at least visible to the medical community in general,” Mackessy points out. “I was happy to see the Gates Foundation funded this study, and if they could be convinced to provide antivenoms in some of these areas, I think that would really facilitate dealing with the problem.” He points out that, in some cases, treating a single venomous snakebite can cost hundreds of thousands of dollars.

“We hope to really provide some focus, and support, for a constructive discussion on where to focus resources for snakebites, whether supporting antivenom development and stocking, or increasing public awareness, and working to identify key at-risk groups, and the snakes responsible,” says Pigott. “As such this work is really a beginning rather than an endpoint.”

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