Commercial antivenom largely ineffective: IISc study

For over a century, anyone bitten by a poisonous snake could take comfort from the belief that a cure in the form of antivenom was available as long as the victim reaches a hospital in time.

Now, a new study by Bengaluru-based scientists from the Indian Institute of Science (IISc), has determined that this commercially available antivenom may be largely ineffective against a variety of snakes.

Major private hospitals and government health centres in India stock “polyvalent” antivenom, which is generally used to treat victims of bites produced by the so-called “big four” snakes - the spectacled cobra, the common krait, the Russell’s viper and the saw-scaled viper. However, a conglomeration of researchers has discovered that this treatment is ineffective against bites inflicted by other, less understood species of snakes.

Kartik Sunagar, an Assistant Professor at IISc’s Centre for Ecological Sciences and senior author of the study published in the journal PLOS Neglected Tropical Disease, said it was folly to continue to use the “big four” antivenom to routinely treat bites from all snakes, considering that India is home to many other species of venomous snakes that have the potential to inflict deadlier, even more fatal bites.

“India is the snakebite capital of the world. About 60 of the 270 species of Indian snakes are considered medically important,” Sunagar said.

To better understand the consequences of using “polyvalent antivenom” to treat all snakebites, researchers conducted a two-stage study. In the first part, they characterised the venoms of major neglected, yet medically important, Indian snakes by their composition, pharmacological activities, and potencies.

These snakes included the Sochurek’s viper, the Sind krait, the banded krait, and two populations of monocled Cobras, as well as their closest “big four”’ relatives (saw-scaled viper, common krait and spectacled cobra).

The results revealed dramatic differences in venom compositions of these snakes. Strikingly, venom composition was also found to differ between geographically separated populations of the same species.

“For instance, stark variation was observed in the venoms of two populations of the same monocled cobra species from West Bengal and Arunachal Pradesh. The former was found to be highly neurotoxic (targeting the nervous system) while the latter was rich in cytotoxins (targeting cells and tissues),” Sunagar said.

‘Startling Results’

In the second part of the study, the research team evaluated how effective commercially marketed Indian antivenoms are in treating snakebites from the neglected species. The results were startling.

The researchers found that the antivenoms were highly inefficient in overcoming the effects of toxins, with one of the antivenoms being completely ineffective against the Arunachal Pradesh monocled cobra. Surprisingly, this widely marketed commercial antivenom even failed to neutralise the venom of one of the ‘big four’ snakes from North India – the common krait.

IISc scientists collaborated with the Gerry Martin Project, which is involved in snake conservation, and the Madras Crocodile Bank Trust and Centre for Herpetology to carry out this study.

Sind Krait found to be most toxic Indian snake

The study found that the venom of the Sind krait from western India is over 40 times more potent than that of the spectacled cobra, making it the most toxic Indian snake. The study also determined that standard polyvalent antivenom was ineffective against venom from this snake.