Snakebite mortality in India: a nationally representative mortality survey

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 antivenom, especially to the 13 states with the highest prevalence, could reduce snakebite deaths in India.

Figure 1. Selected risk factors for snakebite mortality in India (study deaths 2001–03).

Odds ratio after adjusting for age, gender and states with a high prevalence of snakebite deaths (see definition in Table 2). Occupation ‘Other’ includes students and house wives.

Figure 2. Seasonality pattern of snakebite mortality and rainfall in states with high prevalence of snakebite deaths (2001–03).

Rainfall amount (mm) is cumulative daily rainfall for the past 24 hours measured by the India Meteorological Department , . Maximum and minimum temperatures are also measured daily and presented as monthly averages across the 13 snakebite high prevalence states. Pearson correlation coefficients between snakebite mortality and weather were: (i) rainfall; 0.93 (p<0.0001); (ii) minimum temperature: 0.80 (p = 0.0017); (iii) maximum temperature: 0.35 (p = 0.2585).

Figure 3. Estimated deaths and standardized death rates in states with high prevalence of snakebite deaths, 2005.

Death rates are standardised to 2005 UN population estimates for India . The vertical bars represent the state wise estimated deaths (in thousands). Total snakebite deaths for the 13 states with high-prevalence of snakebite death are 42,800 or 93% of the national total (these states have about 85% of the total estimated population of India). States where the snakebite death rate was below 3/100,000 or where populations are less than 10 million are not shown. The states with high-prevalence of snakebite deaths are: AP-Andhra Pradesh, BR-Bihar, CG-Chhattisgarh, GJ-Gujarat, JH-Jharkhand, KA-Karnataka, MP Madhya Pradesh, MH-Maharashtra, OR-Orissa, RJ- Rajasthan, TN-Tamil Nadu, UP-Uttar Pradesh, WB-West Bengal.