In search of a cure

Snakebite could very well be India’s most neglected tropical ‘disease’, says Romulus Whitaker.

June 30, 2012 05:01 pm | Updated 05:01 pm IST

Not enough to go around: Venom being extracted to make the antivenom serum. Photo: M. Karunakaran

Not enough to go around: Venom being extracted to make the antivenom serum. Photo: M. Karunakaran

India has one of the highest rates of death from snakebite in the world. There are four species of snakes (of the nearly 300 different species in India) primarily responsible for deaths. The “Big Four” are the cobra (we have four species), krait (we have eight species), saw-scaled viper (two subspecies) and Russell’s viper. All of these species are widely distributed throughout most of the country although areas like the far Northeast, the Himalayan region and the Andaman and Nicobar have very different snake fauna

The first national survey of the causes of death (the Million Death Study, undertaken in 2001-03 by the Registrar General of India and the Centre for Global Health Research) gave an estimate of 46,000 annual deaths by snakebite in the country. The number of persons permanently maimed by snakebite is not recorded, but it will be significant. Meanwhile, incongruously, the Government of India’s Central Bureau of Health Intelligence reports an annual average of only 1,350 deaths each year for the period 2004 to 2009. This mammoth statistical disparity has severe implications and urgently needs to be addressed.

Laborious process

Antivenom against snakebite is made by injecting gradually increasing doses of purified venom (at present only from the “Big Four”) into healthy horses which build up a high immunity. A quantity of their blood is removed, spun down in centrifuges to remove the serum and the blood cells reconstituted in saline and reinfused into the horses. The serum is purified, tested and freeze-dried (lyophilised) into what is marketed as antivenom by half a dozen pharmaceutical companies in the country.

The venom for producing antivenom is mostly sourced from the Irula Snake-catchers Industrial Cooperative Society located on the premises of the Madras Crocodile Bank on Chennai’s East Coast Road. And herein lies one of the problems. Clinicians in other parts of the country are reporting that the antivenom they are using is ineffectual in counteracting the effects of a venomous bite. Toxinologists, both here and abroad, have found that venom of the same species of snake may differ considerably from region to region which means that the antivenom produced from venom collected by the Irulas in a single district in Tamil Nadu may not be effective in neutralising the venom from the same species of snake from Rajasthan or West Bengal for example.

Professor David Warrell, a world authority on snakebite and co-author of the aspect of the Million Death Study titled “Snakebite Mortality in India”, in a recent editorial in the National Medical Journal of India (Vol.24:6, 2011) states:

“Snakebite accounts for three per cent of all deaths in children of the age of 5-14 years. Ninety-seven per cent of the victims of snake bite die in rural areas, 77 per cent of them outside health facilities, presumably because they chose traditional therapy from tantriks, vaidyas and ojhas. Uttar Pradesh had the highest number of deaths (8700/year) and Andhra Pradesh the highest incidence of mortality due to snake bite (6.2/100000 population/year). These figures should prompt the Ministry of Health to reassess its priorities in the context of snake bite and deploy resources where they are most needed.”

Inaccurate statistics

Professor Warrell goes on to point out the dramatic fact that there is one snakebite death for every two deaths by HIV/AIDS in India! Snakebite is not a “reportable disease” and most victims die outside the hospital. Clearly, statistics from Government hospitals are providing only a fraction of actual mortality figures from snakebite. For example, the government of West Bengal has been paying Rs.1 lakh compensation to families of persons killed by snakebite. In 2011/2012 the total paid was Rs.4,11,00,000, indicating a minimum of 411 reported snakebite deaths a year for that state alone.

While there are few adequate studies on adverse reaction to antivenom in India, statistics from Sri Lanka (where Indian antivenom is widely used) indicate early allergic reactions occurring in 43 to 81 per cent of recipients of Indian antivenom. It is also pointed out that the current antivenom potency requirements (set by Indian Government regulators in the 1950s) of 0.45 to 0.6 mg/ml are woefully inadequate given the venom yields of most of the species responsible for envenoming. India has the cheapest antivenom in the world (averaging Rs.500 per vial), but thanks to its low potency, treatment can actually be very expensive. For example, venom yields for cobras are in the range of 58 to 742 mg which translates to a need for 13 to 165 vials of antivenom (each vial is 10 ml), which would translate to a treatment cost of Rs.6,500 to Rs.82,500!

Since snakebite is a rural problem, primarily affecting India’s farmers, rural labourers and their families, it would make sense for antivenom and associated treatment to be available at Primary Health Centres and other rural medical facilities. However it has been seen that there is no adequate stocking of antivenom at these rural dispensaries and though there are exceptions, training in snake identification and snakebite treatment is woefully inadequate.

Way forward

There are several possible actions that need to be taken to tackle this huge health issue. Firstly, the present production of antivenom, estimated to be close to two million vials per annum, needs to be increased so that adequate supplies are stocked at rural dispensaries around the country and particularly in known snakebite prone areas. Teaching people about snakes, their habits, how to avoid them is of paramount importance. In addition, studies on the efficacy of Indian antivenoms and their improvement, geographic variations in venoms of the same species, species responsible for serious snakebite other than the Big Four are all important measures to come to terms with for what is now recognised as one of rural India’s major and sorely neglected health issues.

The Million Death Study puts it in a nutshell: “Snakebite remains an underestimated cause of accidental death in modern India. 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.”

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