- Though the exact number of snake bites is unknown an estimated 5 million people are bitten each year with up to 2.5 million envenomings.
- At least 100 000 people die as a result of snake bites each year, and around three times as many amputations and other permanent disabilities are caused by snakebites annually.
- Bites by venomous snakes can cause paralysis that may prevent breathing; bleeding disorders that can lead to a fatal haemorrhage; irreversible kidney failure and tissue damage that can cause permanent disability and which may result in limb amputation.
- Agricultural workers and children are the most affected. Children often suffer more severe effects than adults, due to their smaller body mass.
Snake bite is a neglected public health issue in many tropical and subtropical countries. About 5 million snake bites occur each year, resulting in up to 2.5 million envenomings (poisoning from snake bites)1, at least 100 000 2,3 deaths and around three times as many amputations and other permanent disabilities.1 Most of these occur in Africa, Asia and Latin America.2 In Africa alone there are an estimated 1 million snake bites annually with about half needing treatment. This type of injury is often found among women, children and farmers in poor rural communities in low- and middle-income countries. It is mainly in countries where health systems are weakest and medical resources sparse.
Bites by venomous snakes can cause acute medical emergencies involving severe paralysis that may prevent breathing; bleeding disorders that can lead to fatal haemorrhage; irreversible kidney failure and severe local tissue destruction that can cause permanent disability and may result in limb amputation. Children suffer more severe effects than adults due to their smaller body mass.
In contrast to many other serious health conditions, a highly effective treatment exists. Most deaths and serious consequences from snake bites are entirely preventable by making antivenom more widely available. Snake antivenoms are the only effective treatment to prevent or reverse most of the venomous effects of snake bites. They are included in the WHO List of Essential Medicines and should be part of any primary health care package where snake bites occur.
Challenges producing antivenoms
A significant challenge in manufacturing of antivenoms is the preparation of the correct immunogens (snake venoms). At present very few countries produce snake venoms of adequate quality for antivenom manufacture. 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.
A combination of factors has led to the present crisis. Poor data on the number and type of snake bites, leading to difficulty estimating needs, combined with deficient distribution policies, have contributed to manufacturers stopping production or increasing the prices of antivenoms. Poor regulation and the marketing of inappropriate antivenoms, has led to a loss of confidence in the available antivenoms by clinicians, health managers and patients, which has further eroded demand.
Weak health systems and lack of data
Health systems in many countries where snake bites are common lack the infrastructure and resources to collect robust statistical data on the problem. Assessing the true impact is further complicated by the fact that cases reported to health ministries by clinics and hospitals are often only a small proportion of the actual burden because many victims never reach primary care facilities, and are therefore unreported. 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.4
Difficulty estimating need
The poor quantity and quality of data on snake bites is reflected in the poor availability of antivenoms. Poor data results in the under-estimation of antivenom needs by national health authorities leading to low demand for manufacturers to produce antivenom products, and the implementation of inappropriate procurement and medicines distribution strategies in countries.
Low production of antivenoms
Given low demand, several manufacturers have ceased production, and the price of some antivenoms has dramatically increased in the last 20 years, making treatment unaffordable for the majority of those who need it. Rising prices have further suppressed demand, to the extent that treatment has declined significantly or even disappeared in some areas. The entry into some markets of inappropriate, untested or even fake antivenom products has also undermined confidence in antivenom therapy generally. Antivenom supply failure is imminent in Africa and in some countries in Asia.
WHO has taken steps to raise the awareness of health authorities and policy makers on this issue. WHO urges regulators, producers, researchers, clinicians, national and regional health authorities, international and community organizations to work together to improve the availability of reliable epidemiological data on snake bites, the regulatory control of antivenoms and their distribution policies.
Two tools to help guide the development of appropriate antivenoms have been launched:
- WHO guidelines for the production, control and regulation of antivenoms: and
- an online database identifying the worldwide distribution of clinically relevant venomous snakes and their existing antivenoms.
The information will assist:
- public health officials in determining what antivenoms are needed in their country and in drafting relevant national public health policies;
- national medicines regulators in prioritizing antivenoms for registration and assessing safety, quality and efficacy of antivenoms to meet national public health needs;
- procurement agencies in selecting appropriate antivenoms for national treatment needs;
- antivenom manufacturers in developing plans for production and sale of appropriate antivenoms;
- clinicians and health care professionals in treating snakebites; and
- general population in knowing and being able to identify which venomous snakes live in their area.
1Rabies and envenomings: a neglected public health issue. Report of a consultative meeting, World Health Organization, Geneva, 10 January 2007, p14.
2 Chippaux JP. Bulletin of the World Health Organization, 1998, 76 (5), 515-524.
3 Kasturiratne A, Wickremasinghe AR, de Silva N, Gunawardena, NK, Pathmeswaran A, Premaratna R, Savioli L, Lalloo DG, de Silva HJ. The global burden of snake bite: a literature analysis and modelling based on regional estimates of envenoming and deaths, PLoS Medicine, November 2008, Vol. 5, Issue 11, e218.
4 Sharma SK. Snake bites and dog bites in Nepal: community based studies on snake bites and dog bites, Department of Medicine, B P Koirala Institute of Health Sciences, presentation made at the WHO first Consultative Meeting on Rabies and Envenomings, Geneva, 10 January 2007.
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