Differences in snake venom raise questions about treatment

A bite from several of India's most poisonous snakes could be lethal even if a victim had access to the best anti-venom in the Indian market.

This is because researchers from the Indian Institute of Science (IISc) have found different populations of poisonous snakes have differences in their venom composition.

The discovery was made after the researchers studied the venom produced by India's "big four" (the spectacled cobra, the saw-scaled viper, the common krait and the Russell's viper) across six different geographical zones in the country, ranging from Rajasthan to Tamil Nadu. They found major differences in the venom composition, including disparate venom proteomic profiles, biochemical and pharmacological effects, and the associated potencies.

On top of this, the study also found "alarming differences in the efficacy of the marketed polyvalent anti-venoms in neutralising these venoms".

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Assistant Professor Kartik Sunagar of the IISc's Centre for Ecological Studies (CES), who is the corresponding author of the study, explained that the researchers used the increased venom binding of the Premium Serums anti-venom, in comparison to those manufactured by VINS, Bharat Serums and Haffkine, as the baseline for testing.

"The logic is that the Premium Serums anti-venom is the best in the market and if it did not work as expected, then none of the others would," Dr Sunagar explained.

So far as the spectacled cobra was concerned, researchers found that while the anti-venom worked as expected in Tamil Nadu and Karnataka, and better than expected in Andhra Pradesh and Maharashtra, its efficacy fell significantly in West Bengal, Madhya Pradesh and Punjab. The anti-venom failed to completely prevent venom-induced lethality by the desert population of spectacled cobras found in Rajasthan. In the case of Russell’s viper, the efficacy of the anti-venom was substandard in only Punjab.

Sunagar said that in vivo anti-venom neutralising experiments showed "the preclinical ineffectiveness of commercial anti-venom in neutralising the venoms of the North Indian populations of three of the 'big four' snakes."

This partly explains why people in India succumb to snake poison despite anti-venom being available. Annually, India suffers 58,000 fatalities and three times the number of morbidities to snakebites, most of which happen in rural agrarian communities. India's burden of snakebites is the highest in the world thanks to bites from two primary snakes, the spectacled cobra and Russell’s viper (Daboia russelii).

The study was published in the journal, PLOS Neglected Tropical Diseases.