Understanding venom differences from desert to rainforest

Living in India’s countryside, chances are you’ll hear of the Russell’s viper. This thick, brown, chain-patterned snake is responsible for more snakebite deaths and injuries in India than any other species. Every year, thousands of rural farmers and field workers suffer its bite, often with devastating consequences. But not all Russell’s viper bites are created equal. Depending on where you are in India, the venom can act very differently, sometimes attacking blood, sometimes destroying tissue, sometimes triggering life-threatening complications in organs. The same species, but a wildly varied bite. A new study by Navaneel Sarangi, Senji Laxme, and Kartik Sunagar from the Centre for Ecological Sciences at the Indian Institute of Science in Bangalore, explains that climate itself (temperature, rainfall, and seasonal shifts) plays a huge role in shaping the venom. Their work, published in [PLOS Neglected Tropical Diseases], uses predictive modelling to connect weather patterns with venom chemistry. The results could change how doctors treat snakebites across the subcontinent. ### Why venom isn’t the same everywhere? Snake venom is like a living chemistry set. It’s made of dozens of toxins from enzymes that break down tissues, to proteins that disrupt blood clotting, and even molecules that paralyze nerves. The mix isn’t fixed, though. Over time, snakes “tune” their venoms to local conditions to what prey they catch, what predators they face, and, as it turns out, the climate they live in. From the dry deserts of Rajasthan to the lush rainforests of Kerala, the Russell’s viper is spread almost everywhere in India. Farmers in Punjab, fishermen in Tamil Nadu, and tea-pickers in Assam all encounter this snake. But each experience with the bite isn't the same. Victims in the arid northwest may experience heavy bleeding, while those in wetter eastern states may suffer tissue damage or organ failure. For decades, scientists have known about these regional differences but didn’t fully understand why. This study provides one of the first clear answers: climate leaves its fingerprints on venom. The IISc team gathered venom from 115 Russell’s vipers across India, spanning more than 6,600 kilometers of geography. They then tested how active different venom enzymes were. They found three key venom enzymes. PLA₂ enzymes destroy cell membranes and cause tissue damage, Proteases chew through proteins and disrupt blood clotting, and LAAO enzymes damage tissues in subtler ways and can influence bleeding and inflammation. Next, the venom profiles, along with historical climate data from more than a century ago, like average rainfall, seasonal temperature swings, and annual precipitation, were compared. Using statistical models, the researchers checked how well climate variables predicted venom behavior. Finally, they used the models to create “venom maps” of India. These "venom maps" are predictive charts that show where different venom types are likely to occur, based purely on local climate. They found that **no single factor explains venom variation.** In fact, temperature alone or rainfall alone couldn’t account for venom variation. Instead, combinations of climate factors, like shifts in temperature between day and night, or patterns of seasonal rainfall, did. Also, **protease activity (blood-attacking toxins) was highest in dry northwestern India,** so bites in northwestern India are more likely to cause uncontrolled bleeding and blood clotting problems. They also discovered that **PLA₂ activity (tissue-damaging toxins) was higher in wetter regions, like eastern India and parts of the coasts,** meaning that victims in eastern India and parts of the coasts might see more swelling, tissue death, or organ complications. Finally, **LAAO activity was harder to predict.** Climate didn’t seem to shape this enzyme as strongly, suggesting other factors (like diet or genetics) may play bigger roles. Overall, it was found Russell’s viper venom “adapts” to its environment. A snake in the desert carries a different chemical arsenal than one in the rainforest. Right now, India relies on a single type of polyvalent antivenom to treat bites from the “big four” snakes: Russell’s viper, Indian cobra, common krait, and the saw-scaled viper. Because each venom is different, doctors often find that the same antivenom doesn’t work equally well everywhere. This new study points to a solution: region-specific therapies. Doctors in Rajasthan could keep treatments that target protease toxins, while hospitals in West Bengal stock therapies focused on PLA₂ toxins. By tailoring treatment to local venom “flavors,” survival rates could improve dramatically. The researchers even suggest their predictive venom maps could one day guide where to send certain antivenoms, cutting down on wasted doses and saving more lives. Beyond how to address things at the hospital, this study also gives insight into evolution. Snake venom is a dangerous, finely tuned adaptation, shaped by millions of years of environmental pressures. Climate change may also be quietly reshaping venom right now. If temperatures rise or rainfall patterns shift, will snakebites become more dangerous in some areas? Predictive models like these could help scientists see those risks coming. And in this context, the Russell’s viper plays a big role as one of India’s most feared snakes: Because of this study, it’s also becoming one of the most scientifically understood, and its predictive venom maps could transform how doctors prepare for snakebite emergencies, potentially saving thousands of lives each year. If you want to learn more, the original article titled "Significant Serpents: Predictive Modelling of Bioclimatic Venom Variation in Russell’s Viper" on [PLOS Neglected Tropical Diseases] at [https://doi.org/10.1371/journal.pntd.0012949](https://doi.org/10.1371/journal.pntd.0012949). [PLOS Neglected Tropical Diseases]: https://doi.org/10.1371/journal.pntd.0012949

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