Summary
Background Snakebite envenoming is a frequently overlooked cause of mortality and morbidity. Data for snake ecology and existing snakebite interventions are scarce, limiting accurate burden estimation initiatives. Low global awareness stunts new interventions, adequate health resources, and available health care. Therefore, we aimed to synthesise currently available data to identify the most vulnerable populations at risk of snakebite, and where additional data to manage this global problem are needed.
Methods We assembled a list of snake species using WHO guidelines. Where relevant, we obtained expert opinion range (EOR) maps from WHO or the Clinical Toxinology Resources. We also obtained occurrence data for each snake species from a variety of websites, such as VertNet and iNaturalist, using the spocc R package (version 0.7.0). We removed duplicate occurrence data and categorized snakes into three groups: group A (no available EOR map or species occurrence records), group B (EOR map but <5 species occurrence records), and group C (EOR map and ≥5 species occurrence records). For group C species, we did a multivariate environmental similarity analysis using the 2008 WHO EOR maps and newly available evidence. Using these data and the EOR maps, we produced contemporary range maps for medically important venomous snake species at a 5 × 5 km resolution. We subsequently triangulated these data with three health system metrics (antivenom availability, accessibility to urban centres, and the Healthcare Access and Quality [HAQ] Index) to identify the populations most vulnerable to snakebite morbidity and mortality.
Findings We provide a map showing the ranges of 278 snake species globally. Although about 6・85 billion people worldwide live within range of areas inhabited by snakes, about 146・70 million live within remote areas lacking quality health-care provisioning. Comparing opposite ends of the HAQ Index, 272・91 million individuals (65・25%) of the population within the lowest decile are at risk of exposure to any snake for which no effective therapy exists compared with 519・46 million individuals (27・79%) within the highest HAQ Index decile, showing a disproportionate coverage in reported antivenom availability. Antivenoms were available for 119 (43%) of 278 snake species evaluated by WHO, while globally 750・19 million (10・95%) of those living within snake ranges live more than 1 h from Population centres. In total, we identify about 92・66 million people living within these vulnerable geographies, including many sub-Saharan countries, Indonesia, and other parts of Southeast Asia.
Interpretation Identifying exact populations vulnerable to the most severe outcomes of snakebite envenoming at a sub national level is important for prioritizing new data collection and collation, reinforcing envenoming treatment, existing health-care systems, and deploying currently available and future interventions. These maps can guide future research efforts on snakebite envenoming from both ecological and public health perspectives and better target future estimates of the burden of this neglected tropical disease.
Funding Bill & Melinda Gates Foundation.
Copyright c 2018 The Author(s). Published by Elsevier Ltd. This is an Open Access article under the CC BY 4.0 license
www.thelancet.com Vol 392 August 25, 2018
Review of situation in Myanmar
Tha Hla Shwe, Rector (Retd), University of Medicine (2), Yangon
The preceding article by Longbottom et.al. (2018) identified the areas in the world which are highly vulnerable to snakebite envenoming. They described the vulnerability based upon the presence of poisonous snakes, antivenom availability for the prevailing snake species, accessibility to urban centers and Healthcare Access and Quality (HAQ) Index. They described HAQ as “The HAQ Index provides a metric for national levels of personal health-care access and quality, drawing from mortality rates from 32 causes that are amenable to health care.” Based upon HAQ Index score countries were split into ten equally sized groups (deciles), countries in the lowest decile with poor levels of health-care and the highest decile with availability of good health-care. Myanmar falls into the third decile group indicating that a large number of population were at risk of snakebite envenoming and the study estimated that over 2.5 million people were “living within the range of one or more medically important venomous snake species, for which no effective therapy exists, and with a travel time of more than three hours from urban centers with a population of 50,000 or more.”
This finding gave an impetus to undertake a literature review of snakebite situation in Myanmar as far as possible. Quite a number of publications on the topic existed and some of them were reviewed and they showed that snakebite has been recognized and accepted as a public health issue in the country for decades. The available literature dated back to 1970 where a postgraduate student in Preventive & Tropical Medicine submitted a dissertation on” Epidemiology of Snake Bite in Burma” to the Academic Board of the Institute of Medicine 1, Rangoon. This was followed by many studies – epidemiological as well as clinical studies, mainly with Russell’s viper bites, its effects and some clinical considerations. Starting from 2006 the Myanmar Ministry of Health identified snakebite as a priority national health problem in its National Health Plans 2006 – 2011.
A brief summary of the findings from the studies which may be useful for primary care doctors in the districts are presented as follows.
The main species of snakes identified were Russell’s viper, Rat Snake, Cobra, Checkered Keel back, Green Pit Viper, Sea Snake, and Mwe-Pa-Dote. Eighty to ninety percent of snakebites were from Russell’s viper (RV). At this moment anti-snake venom is available only for RV and Cobra..
Incidence (2014 data) – 127 bites/100,000 population in Yangon division, 69/100,000 in Mandalay, 62/100,000 in Magwe, more in men than in women.
Clinical Features of RV bite include: local swelling, local pain, Acute Kidney Injury – oliguria/anuria, heavy proteinuria with some patients needing renal replacement therapy (dialysis?), incoagulable blood, regional lymphadenopathy, abdominal pain, thrombocytopenia, panhypopituitarism, nausea/vomiting, shock.
Prognostic indicators in patients with snakebite include:
– Urine output less than 400 ml in first 24 hours
– Un-clotted blood
– Anti-Snake Venom given more than 2 hours after being bitten
– Bite-to-hospital time more than 2 hours
– Bites in the morning
All of these features are associated with higher case fatality.
Case fatalities ranges from 5.4% in Mandalay, 10% in Yangon and 19% in Magway Divisions (2015 data).
A study by Tin Maung Han et.al. (2009) reported that Low-dose Dopamine and High-dose Furosemide Regime is effective in reversing oliguria induced by viper bite.
Recommendations given include:
– To conduct nation-wide population based study.
– To give ASV within 2 hours after being bitten.
– To apply pressure bandaging and immobilization of affected part as first aid measure.
– Larger supply of ASV and expansion of medical care in rural areas.
– Production of ASV for other species in addition to RV should also be done.
– Community health education especially regarding appropriate first aid.
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Joshua Longbottom, Freya M Shearer, Maria Devine, Gabriel Alcoba, Francois Chappuis, Daniel J Weiss, Sarah E Ray, Nicolas Ray, David A Warrell, Rafael Ruiz de Castañeda, David J Williams, Simon I Hay, David M Pigott
