Envenoming and poisoning by animals: the most neglected of all human diseases
During a career largely devoted to research on neglected tropical diseases, I have encountered the greatest difficulty in persuading scientific colleagues, fellow physicians, international organisations such as the World Health Organization and funding bodies, of the importance and unmet challenge presented by envenoming and poisoning by animals. To admit an interest in this subject has sometimes provoked facetious remarks and inappropriate humour. In some circles I have been branded as merely an entertainer or as a purveyor of esoteric diseases, perhaps colourful and exotic, but scarcely a worthy subject for academic endeavour. However, the accumulation of sound epidemiological data over the past few decades has begun to quantify the burden of human suffering attributable to conditions such as snake bite, scorpion stings, hymenoptera sting allergy and ciguatera fish poisoning. These diseases have proved to be important causes of morbidity and/or mortality in many tropical developing countries, targeting vulnerable and impoverished populations including young children. Even in Western countries that have a sparse toxifauna, envenoming by exotic animals kept (often illegally) as pets and poisoning from eating imported tropical reef fish, are an increasing challenge for inexperienced poisons centres and toxicologists.
I am unrepentant in my passion for these long-ignored diseases. In trying to understand the reasons for their neglect by medical science, one might speculate that an innate primordial fear of snakes and other venomous animals has led to denial or humorous dismissal of the public health problems that they cause. Other more obvious, better publicised and fashionable illnesses have been prioritised to the detriment of support for animal toxin diseases. Below are some examples that should prompt their urgent reconsideration and reprioritisation.
Snake bites in South Asia
Any claim that a disease is unjustly neglected must be built on reliable quantitative evidence that it causes substantial mortality or morbidity. Until recently, community-based data (independent of the notorious underreporting inherent in hospital returns) were available for only a few focal areas of Africa and Asia. For many years, estimates of the burden of snake bite nationally and globally have been calculated by extrapolations within and between countries, resulting in outrageous inaccuracies. However, direct national estimates based on well designed community surveys have now been published. They show annual snake bite mortalities of approximately 6,000 in Bangladesh (Rahman et al. 2010) and 45,900 (95% CI 40,900–50,900) in India (Mohapatra et al. 2011). The figure for India is 30-fold higher than has been declared in official hospital returns published on the Government of India’s web-site (Government of India, Central Bureau of Health Intelligence 2008).
Scorpion stings
Frequent scorpion stings with fatalities especially in children have been reported from North and South Africa, The Middle East, North-Western India, Mexico and South America. A recent review suggested an annual global incidence of more than 1.2 million stings causing more than 3, 250 fatalities (case fatality 0.27%) (Chippaux and Goyffon 2008).
Hymenoptera sting anaphylaxis
Acquired Type 1, IgE-mediated hypersensitivity to the venoms of Hymenoptera (bees, wasps, yellow jackets, hornets, ants) is a common public health problem in most parts of the world. In many countries, stings by Hymenoptera are the commonest cause of anaphylaxis in adults. The incidence of systemic reactions to stings is estimated to be 0.8–5 %, and of severe local reactions 19 %, while the prevalence of hypersensitisation, indicated by the presence of venom specific IgE, detected by skin tests or RAST, may be as high as 25 % of the population. Deaths from Hymenoptera sting anaphylaxis are often unsuspected, undetected and consequently underreported, but this condition kills at least 200 people each year in Europe alone (Müller 2010).
Ciguatera fish poisoning
Ciguatoxins derived from Gambierdiscus dinoflagellates and accumulated in tropical reef fish are the commonest cause of seafood poisoning in Pacific and Caribbean archipelagos, where more than 50% of island populations may be affected. Exposure to ciguatoxins has become globalised as a result of increasing appetites for exotic fish and demands by immigrant populations in Western countries. Endemic ciguatera poisoning has also extended its known geographical limits, to the Eastern Atlantic, Western Gulf of Mexico, Eastern Mediterranean and elsewhere. Estimates of the annual global incidence of ciguatera poisoning range from 25,000 to 500,000 (Dickey and Plakas 2010). Disease recognition is made difficult by the lack of widely available rapid diagnostic assays and ignorance of the distinctive clinical syndrome.
The need for better information and training in Clinical Toxinology
All these examples of the increasing perception of the burden of diseases attributable to animal venoms and poisons should encourage attempts to improve understanding, prevention and treatment - the realm of clinical toxinology. Free, online availability of Junghanss and Bodio’s new “VAPAGuide” will make an important contribution to this strategy. It is being launched at a very opportune moment, when there is increasing demand for up-to-date information on all aspects of clinical toxinology by a new generation of medical professionals which has largely abandoned consulting hard copy books and journals in libraries, in favour of rapidly accessible electronic resources. Built on the pioneering design, many original features and impressively broad database of the 1996 publication “Notfall-Handbuch Gifftiere”, the VAPAGuide will reach a much wider audience. The German word “Gift” does not distinguish between injected “venom” and ingested “poison”, but the language of Goethe, Schiller and Rilke is no less beautiful, powerful and expressive than the language of Milton, Shakespeare and Shelley. However, English is now much more widely understood, making it the appropriate vehicle for the VAPAGuide.
I welcome this new enterprise with great enthusiasm. It greatly expands the information that is readily available to toxinologists, toxicologists, poisons centre consultants, medical practitioners, zoologists and interested lay people, including explorers, travellers, tourists, wilderness enthusiasts and field workers. A challenge will be to keep it updated, abreast of emerging new information in a rapidly expanding field of medical science. I am confident that this is well within the proven capabilities of the VAPAGuide team.
David A. Warrell
Emeritus Professor of Tropical Medicine
University of Oxford, UK
May 2011