Indian Snakebite Panorama: The Mohapatra study

Snakebite Mortality in India: A Nationally Representative Mortality Survey

Citation: Mohapatra B, Warrell DA, Suraweera W, Bhatia P, Dhingra N, et al. (2011) Snakebite Mortality in India: A Nationally Representative Mortality Survey. 

PLoS Negl Trop Dis 5(4): e1018. doi:10.1371/journal.pntd.0001018 

Published April 12, 2011 

https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3075236/pdf/pntd.0001018.pdf

This is an Open Access article.

This study changed the face, created a kind of "new paradigm" on the believes about snakebite related deaths in India.  It is a very rigorous study on snakebite mortality. 

Abstract Background: India has long been thought to have more snakebites than any other country. However, inadequate hospital based reporting has resulted in estimates of total annual snakebite mortality ranging widely from about 1,300 to 50,000. We calculated direct estimates of snakebite mortality from a national mortality survey. 

Methods and Findings: We conducted a nationally representative study of 123,000 deaths from 6,671 randomly selected areas in 2001–03. Full-time, non-medical field workers interviewed living respondents about all deaths. The underlying causes were independently coded by two of 130 trained physicians. Discrepancies were resolved by anonymous reconciliation or, failing that, by adjudication. A total of 562 deaths (0.47% of total deaths) were assigned to snakebites. 

Snakebite deaths:

• occurred mostly in rural areas (97%), 
• were more common in males (59%) than females (41%), and 
• peaked at ages 15–29 years (25%) 
• and during the monsoon months of June to September. 

This proportion represents about 45,900 annual snakebite deaths nationally (99% CI 40,900 to 50,900) or an annual age-standardised rate of 4.1/100,000 (99% CI 3.6– 4.5), with higher rates in rural areas (5.4/100,000; 99% CI 4.8–6.0), and with the highest state rate in Andhra Pradesh (6.2).

Annual snakebite deaths were greatest in the states of Uttar Pradesh (8,700), Andhra Pradesh (5,200), and Bihar (4,500). 

Conclusions: Snakebite remains an underestimated cause of accidental death in modern India. Because a large proportion of global totals of snakebites arise from India, global snakebite totals might also be underestimated. Community education, appropriate training of medical staff and better distribution of anti-venom, especially to the 13 states with the highest prevalence, could reduce snakebite deaths in India. 

The Registrar General of India (RGI) organizes the Sample Registration System (SRS), which monitors all births and deaths in a nationally representative selection of 1.1 million homes throughout all 28 states and seven union territories of India. The number or births and deaths are registered every six months but not the cause of death. What the author's did was to train 800 people that visited each SRS area every six months and recorded a written narrative (in the local language) for each death from families or other reliable informants as well as standard questions about the death. These field reports, or ‘verbal autopsies’, were emailed randomly (based on the language of the narrative) to at least two of 130 collaborating physicians trained in disease coding. 

The data were statistically analyzed and undergone several quality control procedures. 

The data obtained between 2001 and 2003 were applied to the population estimates of the United Nation for India for 2005. According to the author's it doesn't introduce a significant bias to the results. 

RESULTS

DEMOGRAPHICAL DATA

• A total of 562 of the 122,848 deaths from the 1.1 million homes national survey( 0.47% weighted by sampling probability or 0.46% unweighted) were from snakebites. 
• Almost all snakebite deaths (544 or 97%) were in rural areas
• More men (330, 59%) than women (232, 41%) died from snakebites (overall ratio of 1.4 to 1).
• The proportion of all deaths from snakebites was highest at ages 5–14 years
• Only 23% (127/562) of the deaths occurred in a hospital or other healthcare facility. 
• Expressed as national totals, snakebites caused 45,900 deaths in India in 2005 (99% CI 40,900 to 50,900).
• The age-standardised death rate per 100,000 population per year was 4.1 (99% CI 3.6– 4.5) nationally and was 5.4 (99% CI 4.8–6.0) in rural areas.

RISK FACTORS AND SEASONALITY

• Per religion, the risks of snakebite deaths were significantly increased among Hindus.
• Farmers/laborers were the most affected. 
• Deaths occurring outside home
• The monsoon months of June to September show a high number of deaths. 
• Gender and education were not significantly associated with risk of snakebite death

STATE MORTALITY PATTERNS

Annual age-standardised mortality rates per 100,000 from snakebite varied between states, from 3.0 (Maharashtra) to 6.2 (Andhra Pradesh) in the 13 states with highest prevalence (average 4.5) compared to 1.8 in the rest of the country. 

Total deaths were highest in Uttar Pradesh (8,700), Andhra Pradesh (5,200), and Bihar (4,500). The age and gender of snakebite deaths also varied by region, although these differences were not significant due to the small numbers of snakebite deaths in each state. Deaths at ages 5–14 years were prominent in the states of Jharkhand and Orissa, whereas deaths at older ages were prominent in Andhra Pradesh, Bihar, Madhya Pradesh, and Uttar Pradesh (data not shown). In Bihar, Madhya Pradesh, Maharashtra and Uttar Pradesh, female deaths exceeded male deaths

Colors represent prevalence SB deaths/100.000 habitants.
Bars represent the estimated total number of deaths in
thousands. States with SB death below 3/100.000 or with
population less than 10 millions are not shown.

DISCUSSION (I've selected some of the paragraphs):

Snakebite remains an important cause of accidental death in modern India, and its public health importance has been systematically underestimated. The estimated total of 45,900 (95% CI 40,900–50,900) national snakebite deaths in 2005 constitutes about 5% of all injury deaths and nearly 0.5% of all deaths in India. 

It is more than 30-fold higher than the number declared from official hospital returns. 

The underreporting of snake bite deaths has a number of possible causes. 

• Most importantly, it is well known that many patients are treated and die outside health facilities – especially in rural areas. Thus rural diseases, be they acute fever deaths from malaria and other infections or bites from snakes or mammals (rabies), are underestimated by routine hospital data. 
• The true burden of mortality from snakebite revealed by our study is similar in magnitude to that of some higher profile infectious diseases; for example, there is one snakebite death for every two AIDS deaths in India. 
• Very crudely, even if we halve the fatal/nonfatal bite ratio to 32, this would suggest at least 1.4 million non-fatal bites corresponding to the 45,000 fatal bites. The actual number of non-fatal bites in India may well be far higher
• Our study has limitations; notably the misclassification of snakebite deaths. However, snakebites are dramatic, distinctive and memorable events for the victim’s family and neighbors, making them more easily recognizable by verbal autopsy. We observed a reasonably high sensitivity and specificity when compared to re-sampled deaths. Confusion with arthropod bites and stings is unlikely because of the different circumstances, size and behavior of the causative animal and the course of envenoming. 
• Kraits (important agents of snakebite death in South Asia) may unobtrusively envenom sleeping victims, who may die after developing severe abdominal pain, descending paralysis, respiratory failure and convulsions. Such deaths might not be associated with snakebite at all.
• The marked geographic variation across states in our study is similar to that in a country-wide survey conducted during the period 1941–45, which identified Bengal, Bihar, Tamil Nadu, Uttar Pradesh, Madhya Pradesh, Maharashtra and Orissa as having the highest death rates from snakebite. Moreover, despite the obvious underestimates in hospitalized data, their geographical distribution of bites and deaths were similar to what we observed from household reports of deaths. The marked differences in snakebite mortality between states of India may be attributable to variations in human, snake and prey populations, and in local attitudes and health services. 
• The 13 states with the highest snakebite mortality are inhabited by the four most common deadly venomous snakes: Naja naja, Bungarus caeruleus, Echis carinatus and Daboia russelii. With the exception of E. carinatus, which favors open wasteland, these are widely distributed species of the plains and low hills where most Indians live. 
•  As found in an earlier study [33], the peak age group of snakebite deaths is 15–29 years (25% or 142/562). However, the relative risk of dying from snakebite versus another cause was greater at ages 5–14 years. The peak age range and gender associated with snakebite mortality varied between states, perhaps reflecting differences in the relative numbers of children and women involved in agricultural work. 
• The slight excess among Hindus may reflect more tolerance of snakes and greater use of traditional treatments. 
• Snakebites and snakebite fatalities peak during the monsoon season in India and worldwide , probably reflecting agricultural activity, flooding, increased snake activity, and abundance of their natural prey. 
• Only 23% of the snakebite deaths identified in our survey occurred in hospital, consistent with an earlier study from five states. This emphasizes three points: 

1. Hospital-based data reflect poorly the national burden of fatal snakebites; 
2. Inadequacy of current treatment of snakebite in India; and 
3. Vulnerability of snakebite victims outside hospital. 

PRACTICABLE SOLUTIONS INCLUDE:

• Strengthening surveillance to allow a more accurate perception of the magnitude of the problem, 
• Improving community education to reduce the incidence of snakebites and 
• Speed up the transfer of bitten patients to medical care, 
• Improving the training of medical staff at all levels of the health service (including implementation of the new WHO guidelines), and 
• Deployment of appropriate antivenoms and other interventional tools where they are needed in rural health facilities to decrease case fatality. In addition, 
• Phylogenetic and venom studies are needed to ensure appropriate design of antivenoms to cover the species responsible for serious envenoming

ॐ लोकाः समस्ताः सुखिनो भवन्तु ॥

Om Lokah Samasthah Sukhino Bhavantu

May all beings everywhere be happy and peaceful.