Sunday, 29 January 2012

Why is the land of snakes, so inept at dealing with snake bites? (via Herp Digest)

The number of people who died of snakebite in India was not known for decades. But there was no doubt thousands perished. This was, after all, the proverbial land of snakes. Finally, in April last year, a study estimated about a million people were bitten by snakes and approximately 46,000 died annually. These first reliable figures illustrate the enormity of the problem rural people face in this country. We also know more people are killed by snakes in India than any other country in the world.

Snakebite is a major occupational hazard in a country where farmers typically walk barefoot along field bunds. While we can exhort them to wear footwear, it will take years for this long-observed practice to change. People also tend to walk in the dark without a torch. For several decades, the price of disposable batteries was prohibitive for ordinary villagers, but the use of the new, affordable Chinese-made rechargeable torches may reduce the death toll. The other habit that puts rural people in harm's way is sleeping on the floor. When farm economy is floundering, advising them to sleep on bedsteads will only elicit blank, uncomprehending stares. If people get bitten and are rushed to the hospital, the lack of doctors, trained in treating snakebite, as well as the limited availability and effectiveness of antivenom serum, jeopardize their lives further.

The only way to save a person from a lethal venomous snakebite is the administration of antivenom serum, even though too many people rely on superstition and alternative forms of medicine. Indians have had a surefire way of surviving a lethal bite as early as the 1920s, when the Central Research Institute began producing this life-saving drug commercially. Yet, almost a century later, despite snakebite continuing to be a major public health crisis, the availability of antivenom serum in small towns and villages, where bites usually occur, is limited.

Six manufacturers produce a serum made from the venoms of the Big Four: cobra, common krait, Russell's viper and saw-scaled viper. Despite advances in antivenom production techniques, those of the Indian companies remain relatively unchanged since the 1950s. Several international publications have criticized Indian antivenoms for their impurity and for causing complicating side effects.

All the companies claim identical potency for their antivenom serums, which is astonishingly low. This means many more vials are needed to neutralize the harmful effects of a venomous snakebite. One study says a person needs an average of 51 vials to treat cobra and krait bite, while 32 vials are needed to treat Russell's viper bite. Another study quoted as much as 91 vials being used to neutralize cobra and krait bites. Such high doses of impure antivenom serum can potentially cause adverse reactions. In Sri Lanka, up to 87% of snakebite victims who were treated with Indian antivenom developed untoward side effects.

A standard clinical procedure to validate the claimed potency values has never been published. Inexplicably, prior to the mid-1950s, antivenom serums were much more potent than those currently available. It's not clear why the Indian authorities lowered the standards.

The low potency and high adverse reactions have raised doubts about the effectiveness of Indian antivenom serum. Venom is a protein-rich soup with numerous toxins, peptides and enzymes. What snakes eat determines the combination and proportion of these elements in their venom. In many species, the venom of young snakes, which eat small creatures like frogs, undergoes a transformation as they grow older and switch to eating larger animals like rodents. Where they live also appears to influence the kind of venom they produce, even within a species. For instance, the venom of Russell's vipers in south India is quite different from the north. So antivenom made with the venom of a southern viper may not work against the same species in other parts of the country.

Indian antivenom is produced for four snakes against the World Health Organization's (WHO) list of twelve high-priority species for South Asia. In short, we do not know what coverage the antivenom serum has. Does it neutralize the bites caused by the young of the same species, and is it as effective anywhere in the country. Does the serum made for the Big Four counteract the venom of any others? In the absence of these tests, physicians have no choice but to try and save the lives of their patients with the only tool they have.

In 2010, WHO recommended a set of standard procedures for the assessment and evaluation of antivenoms anywhere in the world. David Williams, a clinical toxinologist working with the Global Snakebite Initiative, says Indian antivenom has to be tested for effectiveness against the high-priority snake species. Only then can doctors be sure that the treatment they are providing their patients, which is often expensive and beyond poor people's means (between Rs. 450 and 500 a vial), is effective.

Williams further advises that once the lack of effectiveness of the available antivenom serum is established, if the problem cannot be fixed easily, then a new start has to be made to produce a broad-spectrum antidote for the entire region. Several manufacturers should be licensed to produce this life-saving drug. Antivenom should be distributed free or at heavily subsidized rates through the public health system. In Tanzania, people sought antivenom treatment much more readily when it was provided free, which indicates their reliance on traditional medicine and superstition is at least partly driven by cost considerations.

Indian health authorities must recognize snakebite for what it is: a neglected tropical disease that maims and kills tens of thousands of poor people. While the WHO acknowledged this fact in 2009, snakebite is yet to feature in any of the organization's programs. Besides the development of an effective antivenom serum and training doctors, a major awareness campaign needs to be launched to teach people to avoid being bitten by snakes, as well as the appropriate first-aid practices to follow in the event of a bite. India has to overcome poor governance, abysmal regulation of antivenom quality, and social inequity to arrest the unconscionable loss of lives to snakebite

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