India’s snakebite regime found wanting

Antivenoms commercially available in India are inefficient in treating the effects of many snakebites, researchers say.

Writing in the journal PLOS Neglected Tropical Diseases, a team led by Kartik Sunagar from the Indian Institute of Science reports that while antivenoms remain the mainstay of snakebite therapy, studies in mice show they fail to neutralise the toxins of many venomous snakes.   

Each year, snakebites kill 46,000 people in India and disable 140,000 others. 

The states with the highest mortality are inhabited by the so-called Big Four of venomous snakes: the spectacled cobra, the common krait, Russell’s viper, and the saw-scaled viper. However, India has almost 300 snake species and around 60 of these are venomous.

Despite this, there are few species-specific antivenoms. Instead, the antivenoms designed for the Big Four are routinely used to treat bites from all snakes. 

To find out the implications of this, Sunagar and colleagues carried out a two-part study. 

In the first part they analysed the protein composition and toxicity profiles of the venoms of the major Indian snakes. They found they contain a wide range of toxins with profound compositional diversity between different snake species and even in a single species. Such diversity is due to the snakes’ dissimilar habitat and diet. 

In the second part, they tested in mice the effectiveness of commercial antivenoms in dealing with the different toxic effects, and found they often fell short of expectations.

For example, antivenoms designed to neutralise venom from the spectacled cobra from western Maharashtra state did so effectively, but were much less successful when used for venoms of monocled cobra from eastern and northeastern India, they report. 

The antivenoms were particularly ineffective against the venom from east Indian snakes. In one example, the researchers say, an antivenom completely failed to neutralise monocled cobra venom from northeast India, despite it being the least toxic among the cobra venoms tested. 

The researchers also report that Indian antivenom manufacturers don’t always stick to international production standards, which can lead to inefficient antivenoms being released.