Local climate can be used to predict the venom characteristics of a deadly snake that is widespread in India, helping clinicians to provide targeted therapies for snake bite victims, according to a study publishing April 10 in the open-access journal PLOS Neglected Tropical Diseases by Kartik Sunagar and colleagues at the Indian Institute of Science.
Russell's viper (Daboia russelii) is found across the Indian subcontinent and is responsible for over 40% of snake bite-related deaths in India each year. Its venom is extremely variable, and snake bites cause different symptoms in different regions of India. The toxic effects of snake venom are caused by the concentrations of different enzymes, which can be influenced by many factors, including prey availability and climate. However, the factors driving variation in Russell's viper venom are unknown.
To investigate, researchers analyzed venom samples from 115 snakes collected in 34 locations across India. They tested the activity of venom toxins, including enzymes that break down proteins, phospholipids and amino acids. Next, they used historical climate data to understand the relationship between venom composition and the local climate where the snakes were caught. They found that temperature and rainfall partly explained regional variation in snake venom composition. Protease activity showed the closest relationship to climate variables, whereas the activity of animo acid oxidases was unaffected by climate. Snakes in drier regions of India tended to have higher protease activity. The researchers used this data to create a map of expected venom types across Russell's viper's range in India, which could be used to predict the clinical symptoms of snake bites in different regions.
The venom maps developed in this study could help clinicians select the most appropriate treatment for patients with snake bites, or to develop targeted therapies such as toxin-specific antibodies, the authors say.
Author Kartik Sunagar adds: "Russell's viper is arguably the clinically most important snake species in the world. It kills and maims more people than any other snake species. As a result, it is important to precisely unravel the composition, activity, and potency of Russell's viper venoms and understand the role of biotic and abiotic factors in shaping them. Recent studies from our lab have shed light on the influence of biotic factors, such as developmental shifts in diet, on Russell's viper venom composition and toxicity. However, the effects of abiotic or environmental factors remained unstudied. Here, we highlight, for the first time, the role of climatic conditions, such as temperature, humidity and rainfall, in driving the biochemical functions of Russell's viper venoms."
