Snakebite envenoming

Primary reference(s)

WHO, 2013. Snakebite Envenoming. World Health Organization (WHO). Accessed 15 February 2025.

Annotations

Key relevant UN convention / multilateral treaty

Not identified.

Drivers

Snakebite envenoming is a potentially life-threatening disease caused by toxins in the bite of a venomous snake. Envenoming can also be caused by having venom sprayed into the eyes by certain species of snakes that have the ability to spit venom as a defence measure (WHO, no date).

Inadequate past efforts to control snakebite envenoming have produced fragmented, inaccurate epidemiological data. Many victims do not attend health centres or hospitals and instead rely on traditional treatments. However, available data show that 4.5-5.4 million people get bitten by snakes annually. Of this, 1.8-2.7 million develop clinical illness and 81,000 to 138,000 die from complications (WHO, no date).

High-risk groups include rural agricultural workers, herders, fishermen, hunters, working children, people living in poorly constructed houses and those with limited access to education and healthcare. Morbidity and mortality occur most frequently among young people and children suffer higher case fatality. Furthermore, women experience increased barriers to accessing medical care in some cultures and pregnant women are extremely vulnerable (WHO, no date).

An ongoing crisis restricting access to safe, effective antivenom treatment in many regions, particularly sub-Saharan Africa, is one factor that contributes to the predisposition to seek help through traditional medicine (WHO, no date).

Impacts

Bites by venomous snakes can cause acute medical emergencies involving severe paralysis that may prevent breathing, cause bleeding disorders that can lead to fatal haemorrhage, cause irreversible kidney failure and severe local tissue destruction that can cause permanent disability and limb amputation. Children may suffer more severe effects and can experience the effects more quickly than adults due to their smaller body mass (WHO, 2023). 

Multi-hazard context

Envenoming affects women, children and farmers in poor rural communities in low- and middle-income countries. The highest burden occurs in countries where health systems are weakest and medical resources are sparse (WHO, 2023). An increased incidence of snakebite envenoming may be associated with the following natural hazards (floods, earthquakes, volcanic activity, typhoons, hurricanes and cyclones, landslides, tsunami events), the extractive industry (mining, forestry), and land use (agricultural activity like rice, sugar cane, oil palm, copra, rubber, tea, coffee, banana plantations and other agribusiness involving manual labour) (WHO, 2023).

Risk Management

In contrast to many other serious health conditions, a highly effective treatment exists for envenoming. Most deaths and serious consequences of snake bites are entirely preventable by making safe and effective antivenoms more widely available and accessible. High-quality snake antivenoms are the only effective treatment to prevent or reverse most of the venomous effects of snake bites (WHO, 2019). Issues include: 

• A significant challenge in manufacturing antivenoms is the preparation of the correct immunogens (snake venoms). At present very few countries have the capacity to produce snake venoms of adequate quality for antivenom manufacture, and many manufacturers rely on common commercial sources. These may not properly reflect the geographical variation that occurs in the venoms of some widespread species. In addition, lack of regulatory capacity for the control of antivenoms in countries with significant snake bite problems results in an inability to assess the quality and appropriateness of the antivenoms (WHO, 2023).
• A combination of factors has led to the present crisis. Poor data on the number and type of snake bites have led to difficulty in estimating needs, and deficient distribution policies have further contributed to manufacturers reducing or stopping production or increasing the prices of antivenoms. Weak regulation and the marketing of inappropriate or poor quality antivenoms have also resulted in a loss of confidence in some of the available antivenoms by clinicians, health managers, and patients, which has further eroded demand (WHO, 2023).
• Snake antivenom immunoglobulins (antivenoms) are the only specific treatment for envenoming by snakebites. Antivenoms can prevent or reverse most of the snakebite envenoming effects and play a crucial role in minimising mortality and morbidity. These preparations are included in the WHO List of Essential Medicines and should be part of any primary health care package where snakebites occur. Currently, there is an urgent need to ensure the availability of safe, effective and affordable antivenoms, particularly to people in developing countries, and to improve the regulatory control over the manufacture, import and sale of antivenoms (WHO, 2018).  

The WHO has taken steps to raise the awareness of health authorities and policymakers on this issue. In December 2015, a programme to evaluate the potential safety and effectiveness of current antivenom products intended for use in sub-Saharan Africa was launched by the WHO. The results of this detailed technical and laboratory assessment will provide procurement agencies with informed guidance on which antivenoms best suit their needs. Following a request by several United Nations member states, the WHO formally listed snakebite envenoming as the highest priority neglected tropical disease in June 2017 (WHO, 2023). 

Regional engagement by the WHO has taken place and various resources are now available. 

• The guidelines for the Prevention and Clinical Management of Snakebite in Africa were developed by the WHO Regional Office of Africa with contributions from technical experts. They are meant to assist health workers to improve medical care for snakebite victims. The guidelines discuss snakes, snake venoms and snakebites and their consequences with emphasis on the medically important snakes, namely those causing serious envenoming. The volume contains over a hundred snake photographs, clinical signs of envenoming and the consequences. The guidelines also feature various annexes and in particular the geographical distribution of African venomous snakes, as well as their classification, habitats and clinical toxinology (WHO, 2010).
• The incidence of snakebite mortality is particularly high in South-East Asia. Rational use of snake anti-venom can substantially reduce mortality and morbidity due to snakebites. These guidelines are a revised and updated version of the Regional Guidelines for the Management of Snakebites published by the WHO Regional Office in South-East Asia in 2011 and updated in 2016. These guidelines aim to promote the rational management of snakebite cases in various health facilities where trained health functionaries and quality snake antivenom are available (WHO, 2013). 

A Snakebite Envenoming Working Group established that same year was tasked with informing the development of a strategic WHO road map on snakebites. This strategy focuses on a 50% reduction in mortality and disability caused by snakebite envenoming by 2030. This aim will be achieved through four key objectives: empower and engage communities; ensure safe, effective treatment; strengthen health systems; and increase partnerships, coordination and resources (WHO, 2023). 

Monitoring

Under-reporting of snake bite incidence and mortality is common, examples include reports from Nepal, India and Sri Lanka:

• In Nepal, for example, where 90% of the population lives in rural areas, the Ministry of Health reported 480 snake bites resulting in 22 deaths for the year 2000 yet figures for the same year collected in a community-based study of one region (eastern Nepal) detailed 4078 bites and 396 deaths (Sharma et al., 2004).
• A very large community-level study of snakebite deaths in India gave a direct estimate of 45,900 (99% CI: 40,900-50,900) deaths in 2005, which is over 30 times higher than the Government of India's official figure (Mohapatra et al., 2011). Revised estimates based on verbal autopsies and other data now suggest that as many as 1.2 million Indians died from snakebite envenoming between 2000-2019 (an average of 58,000/year) (Suraweera et al., 2020).
• A comparison of hospital-registered deaths in one district of Sri Lanka to data from the Registrar-General's office on deaths demonstrated that 62.5% of deaths from snakebite envenoming were not reported in hospital data (Fox et al., 2006).