Bothrops asper is considered the most dangerous snake in Central America. (Image: Dogymho, Creative Commons Attribution 2.0 Generic license)

Can plants be used to treat snakebites?

Peter Giovannini and Melanie-Jayne Howes in Kew’s Natural Capital and Plant Health Department assess the scientific evidence supporting the local use of plants to treat snakebites.

Date: 
27 February 2017
Blog team: 
Author: 
Peter Giovannini & Melanie-Jayne Howes

 

A neglected public health issue

Worldwide, an estimated five million people are bitten by snakes each year. Of these, about 400,000 are left permanently injured and up to 100,000 die.

Although snakebite envenoming is a significant public health issue, particularly affecting people living in rural areas with scarce access to modern healthcare, it is considered a neglected disease because of the lack of attention from policy makers and health authorities. According to the World Health Organisation (WHO), the greatest percentage of snakebites occur in children and agricultural workers, thus the burden of the disease is considerable in terms of disability-adjusted life years and in terms of economic costs (WHO, 2007).

Regional estimates of envenomings due to snakebites (low estimate) (Image: Wikimedia commons based on data by Kasturiratne et al., 2008).

Local use of medicinal plants for snakebites

Several studies report the local use of a range of plant species to treat snakebites. These studies are frequently conducted in rural areas where access to anti-venom treatments is often limited, due to the cost and the necessity to keep the anti-venoms at low temperatures (usually referred to as the “cold chain”).

Considering the widespread use of medicinal plants as remedies for snakebites, and the need to understand the most useful of these species to help snakebite victims, it is important to assess the available evidence to understand the scientific basis for their use.

Medicinal plants to treat snakebites in Central America

Around 40 species of venomous snakes are known to exist in Central America: pit vipers (Viperidae), yellow-bellied sea snake, coral snakes (Elapidae) and colubrids (Colubridae). An estimated 5,500 snakebite cases are reported by health centres in Central America each year. Moreover, the population living in this region maintains a strong tradition in using medicinal plants, including ‘snakedoctors’ - traditional healers specialised in treating snakebites.

We recently conducted a study to determine which plant species are used to treat snakebites, by scrutinising numerous published studies on medicinal plants used in Central America, including Belize, Costa Rica, El Salvador, Guatemala, Honduras, Nicaragua and Panama. We compiled the results in a database, evaluating information on the chemistry and possible modes of action of the key plant species and their constituents, to gain new insights into the scientific evidence that might explain their use. For example, some plants may provide symptomatic relief for snakebites by reducing pain or inflammation, others might be used for their reputed sedative and anti-anxiety effects to target the panic and fear in victims, whilst others might have anti-venom properties or may be used to target the effects of snake venom on blood clotting or on nerve function.

Bothrops asper is considered the most dangerous snake in Central America. (Image: Dogymho, Creative Commons Attribution 2.0 Generic license)

More than 200 plant species used to treat snakebites in Central America

We found 208 species, spread across 74 plant families, used to treat snakebites in Central America. However, only nine of these species were reported independently in at least three studies; these were: Piper amalagoCissampelos pareiraAristolochia trilobataSansevieria hyacinthoidesScoparia dulcisStrychnos panamensisDorstenia contrajervaHamelia patens, and Simaba cedron.  

Cissampelos pareira, a widely used medicinal plant in Central and South America. (Image: L. Shyamal, licensed under the Creative Commons Attribution-Share Alike 3.0 Unported license).

We concluded that documenting the traditional uses of medicinal plants, such as those used against snakebites, not only assists with the preservation of traditional knowledge, but is also important to guide future studies on the chemical and biological activities of plant species to understand their current, traditional and potential uses. We also emphasise the importance of not only recording the plant species and their traditional uses, but also more specific details, including the plant part(s) used, the route(s) of administration, such as internal or external use, the method of their preparation and an indication of the dose.

In our study, we found that some evidence appears to provide a scientific explanation for the use of some plant species for snakebite in Central America. However, this evidence is limited and is based on laboratory studies only. More extensive investigation is needed, particularly to evaluate the efficacy and safety of these plant species in humans (clinical studies).

Biological mechanisms are poorly understood

Furthermore, additional research to investigate the scientific basis of snakebite remedies is needed, to provide a greater understanding of their biological mechanisms to aid the discovery of new compounds with biological activity. This research will also be useful to explore the possibility of developing low-cost treatments based on plant extracts and for identifying remedies that are potentially unsafe. For example, reserpine, a compound used as an antihypertensive medication was isolated for the first time from the root of the plant known as Indian snakeroot (Rauvolfia serpentina). In addition to the discovery of this new drug for high blood pressure, research on the compounds from Indian snakeroot led also to a better understanding of some of the ‘chemical messengers’ in the brain that are involved in the pathology of depression.

Our review of medicinal plants used to treat snakebites in Central America shows that many species are used across the region, suggesting a widespread use by people living in rural communities where anti-venoms are often not available, although more evidence for their efficacy and safety is needed. 

- Peter & Melanie-Jayne -


References

Giovannini, P. & Howes, M.-J.R. (2017). Medicinal plants used to treat snakebite in Central America: Review and assessment of scientific evidence. Journal of Ethnopharmacology 199: 240–256 DOI: 10.1016/j.jep.2017.02.011. Available online

Map:

Kasturiratne, A., Wickremasinghe, A. R., de Silva, N., Gunawardena, N. K., Pathmeswaran, A., Premaratna, R., Savioli, L., Lalloo, D. G. & de Silva, H. J. (2008). The global burden of snakebite: a literature analysis and modelling based on regional estimates of envenoming and deaths. PLoS Med DOI:10.1371/journal.pmed.0050218. Available online