Venom code

Taking the wrong anti-venom could be dangerous too

Published: Monday 15 August 2005

Venom code

-- Most people react to snakes with fear. Yet, very few snakes are lethal or even poisonous. India, in fact, has only five known varieties of deadly snakes: cobra, krait, Russell's viper and saw-scaled viper, and the recently discovered hump-nosed pit viper. A small brown snake with markings in lighter/darker brown, the pit viper or chirutta inhabits deciduous and secondary forests across the western ghats, in Kerala, Tamil Nadu, Karnataka, Goa, Maharashtra and Andhra Pradesh.

Previously, it was believed to be harmless, but now Joseph K Joseph, Little Flower Hospital, Angamaly, Kerala and Ian D Simpson, a herpetologist in the World Health Organization's snakebite treatment group, has found its bite to be fatal. The pit viper's bite takes effect after twelve hours, what Simpson calls its 'Cinderella' gestation.

Every year, more than 50,000 people across the globe die as a result of snakebite. These vary in their effects. Neurotoxic bites paralyse the respiratory organs, leading to suffocation and then death. Cobra and krait bites are of this type. Viper bites are haemotoxic -- they destroy the clotting ability and the victim bleeds to death.

The serum route However, most snakebite deaths in India are preventable with anti-venoms. These are serums produced by injecting a small amount of the venom from a snake into a horse. Then, antibodies from the horse are extracted and purified. When these proteins are given to the patient, they hook on to the poison in the patient's body and trap it. However, anti-venoms are not easily available and are expensive too. Often, they do not work after being administered, as they need to pass through a cold chain to be effective.

Anti-venoms have other problems. Administering the right quantity is critical, as anti-venoms often have serious side effects on vital organs when unwanted protein enters the bloodstream. They can also cause anaphylactic reactions -- people allergic to horse protein may go into shock and even their respiratory systems may shut down. The other problem -- quite common in India -- is that impurities often get left behind in the anti-venom during the manufacturing process. These can end up causing unpleasant reactions.

Who-dun-it Identifying the snake is a prerequisite to finding the appropriate anti-venom. But to do this, doctors are usually forced to go by the patient's description or keep a bank of dead snakes for patients to look at and identify. As these methods are somewhat unreliable, the more common practice has been to use a polyvalent anti-venom -- a common vaccine that is effective against the venom of all the four big snakes.

Other countries use monovalent anti-venoms, specific to each snake. Using an identification technology called elisa (enzyme-linked immunosorbent assay), doctors test samples taken from the wound discharge to identify the snake type and check the quantity of poison that has entered the body. This helps decide the quantity of anti-venom to be administered.

elisa may be in India by the end of the year, thanks to a project funded by the Kudremukh Iron Ore Company Limited and guided by the universities of Oxford and Liverpool, uk. "Indian pharmaceutical companies can make anti-venoms and the stakes used for testing snakebites at a reasonable price," says Simpson, adding that elisa ensures proper treatment and patients don't need to go in for costly drugs.

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