How Land Transformation and Migration Could Impact the Public Health Crisis Caused by Venomous Snakes


The World Health Organization (WHO) considers snakebite envenoming–the potentially life-threatening disease caused by toxins from a venomous snake–a Neglected Tropical Disease.

Globally around 5.4 million people are bitten by venomous snakes every year, with snakebites killing between 81,000 and 138,000 people each year–more than dengue and rabies combined. An additional 400,000 of those bitten survive with an amputation or permanent disability, and these reports are likely a gross underestimate. 

Most of the snakebite victims are rural agricultural workers with few resources, living in middle- to low-income tropical countries. Due to its high prevalence and severe under-recognition, international agencies such as the WHO, the Global Snakebite Initiative, and Doctors Without Borders are working to raise awareness and develop solutions for the millions of people impacted by snakebite envenoming.

To best address this crisis, policymakers and public health authorities should consider using a comprehensive systems-based approach, such as a One Health approach, where human, animal, and ecosystem health perspectives are integrated, can be used by policymakers and public health practitioners to design long-term solutions and mitigate the burden of snakebite envenoming. One Health can help to ensure the health and well-being of people, animals, and the environment. Some USAID activities apply a One Health approach, including Africa RISING, an agroforestry initiative, and Health, Ecosystems, and Agriculture for Resilient, Thriving Societies (HEARTH), a multisectoral program that aims to conserve high-biodiversity landscapes and improve community well-being.

The burden of snakebites is predicted to worsen with climate change, population growth, and land-use change. Natural disasters such as hurricanes and floods are linked to higher rates of snakebites following the event–as snakes are swept from their nests or out of their home ranges by flooding or habitat disturbances, they often seek shelter in or near human dwellings. These weather events may also increase stress levels in snakes, rendering them more likely to strike.

The changing climate is altering the distribution and abundance of certain species, especially cold-blooded animals such as snakes. Herpetologists in Costa Rica and Mozambique, for instance, are reporting the presence of venomous species at higher elevations than in past decades.

Forced human migration is also considered a risk factor for snakebite. In tropical migration routes such as the Darien gap linking Colombia and Panama, snakebites are among the many dangers that migrants face. When fleeing violence, migrants are often forced to hide in brushy areas where snakes hide. While on the move or in camps, people have little to no access to healthcare. Migrant workers are also vulnerable to poor labor conditions, working barefoot or at night, when snakes are most active. 

Land use change and urbanization are making snakebites more prevalent. With the loss of native habitat and prey, some snake species seek refuge and sustenance in urban areas, where rats and pigeons are easy to find. This increased human-snake interface raises the risk for envenomations. 

Habitat destruction for agriculture may also increase the public health risk of snakebites. Monocultures support few species compared to balanced ecosystems, but there are often a couple of species that thrive and overpopulate single crop plantations. The ensuing insect and rodent pest infestations attract hungry snakes in search of prey. Across the Americas and Africa, researchers have found that monocultures of African oil palm and pineapple augment the densities of certain snake species compared to natural habitats. Many workers suffer bites on their hands and legs while working on plantations.

Even with the gold-standard of treatment, antivenom, victims are often left with permanent disabilities. With the burden and costs of snakebite envenomation growing, it is important to understand and mitigate the converging risk factors. One Health provides a framework to facilitate collaboration across sectors to synergize technical expertise and resources to prevent bites before they happen. 

For instance, landscape ecologists and biologists who understand snake behavior and climate impacts provide critical insights about where risk of human-snake interactions may increase and how to best avoid being bitten. Public health and governance officials assist communities to strengthen health services, message opportunities to change risky behaviors, and prevent underlying drivers of migration and inequalities, particularly for the most vulnerable people. Climate-smart, sustainable agriculture, such as silvopastoral systems, provide habitat for a healthy mix of biodiversity that prevents overabundance of rodent pests that attract snakes. 

Two herpetologists at the Instituto Clodomiro Picado in San Jose, Costa Rica extracting venom from a bothrops asper.

Jazmín Sánchez Arias and Greivin Corrales, herpetologists at the Instituto Clodomiro Picado in San Jose, Costa Rica extracting venom from a bothrops asper. Photo Credit: Chloe Vasquez

One Health interventions have worked for mitigating similar issues. In Egypt, more diverse ecosystems have supported mongoose populations that control snake infestations. Meta analyses from around the world suggest that agroforestry successfully reduces plagues compared to monoculture plantations.

After antivenom dispersion, ecological and health education campaigns, and an environmentalist revolution, Costa Rica’s snakebite trend has plummeted over the past half-century, from a mortality rate matching modern lung cancer (about 2.6 deaths due to snakebite per 100,000 Costa Ricans), to 1-2 per 5 million inhabitants. In Nepal, USAID supports raising public awareness on the risks and prevention measures stemming from natural disasters, including snakebites.

USAID is well positioned to capitalize on its broad technical expertise to provide effective and integrated One Health solutions to prevent snakebite envenomation and other Neglected Tropical Diseases.

ABOUT THE AUTHOR: Chloe Vasquez is a Virtual Student Federal Service intern with USAID. She studies Economics, Political Science and Global Health at Macalester college, and conducts research on snakebite in Mexico.