Baby Saw-Scaled Vipers Rewrite the Rules of Venom
One of the most fascinating aspects of studying venoms is that they are not static. They change with geography, diet, and even the age of the snake. In our study, my team and I uncovered a dramatic example of this in the Egyptian saw-scaled viper (Echis pyramidum pyramidum), one of the deadliest snakes in the world.
Saw-scaled vipers are responsible for countless deaths across Africa and Asia, primarily through a condition called venom-induced consumptive coagulopathy. Their venoms drive the body into catastrophic clotting, depleting clotting factors until victims are left unable to stop bleeding. What hadn’t been investigated until now was whether neonates and adults of the same species deploy their venoms in the same way.
Venoms that grow up with the snake
We compared venom from neonates—just one month old—to that of adults. Both venoms were procoagulant, but the difference in potency was striking. The neonate venom was over 600% more potent than the adult venom in clotting human plasma. Despite delivering smaller amounts of venom, a bite from a neonate could therefore be every bit as medically severe as one from an adult.
The underlying biochemistry also shifted. Neonate venom potently activated Factor VII and Factor X, with some effect on Factor XII. Adult venom, in contrast, barely touched Factor X, was weaker on Factor VII, and only comparable on Factor XII. This is the first time Factor VII and XII activation has been documented in any Echis venom.
Why this matters for treatment
These differences carry direct consequences for snakebite treatment. We tested five different antivenoms and saw a clear pattern: all were less effective against neonate venom. The South African SAVP-Echis antivenom performed the best, but even it neutralized adult venom more efficiently than neonate venom. Others—particularly those raised against West African Echis—barely worked at all.
This highlights a crucial point: most antivenoms are made using venoms from adult snakes. If neonate venoms have different toxins and greater potency, then patients bitten by young snakes may be at even higher risk of poor outcomes. Our results argue strongly that neonate venoms need to be incorporated into immunizing mixtures if we want antivenoms to provide full coverage.
Ecology driving evolution
The ecological story behind this is just as interesting. Juvenile and adult snakes often feed on very different prey. Young Echis take smaller, faster prey such as arthropods and amphibians, where rapid incapacitation is essential. Adults feed on larger mammals, and their venom reflects a slower, but still deadly, strategy. In other words, the venom evolves in step with the snake’s changing ecological niche.
A dynamic biochemical arsenal
This study underscores something I’ve emphasized for years: snake venoms are dynamic evolutionary tools, not fixed traits. They shift across geography, between species, and within an individual’s lifetime. For clinicians, this makes the challenge of developing effective treatments far greater than simply “matching the right species.” For evolutionary biologists, it shows again just how remarkable venoms are as adaptive traits.
Snakebite remains a neglected tropical disease, devastating rural communities across Africa and Asia. By understanding venom variability—including these age-related changes—we can design better antivenoms and, ultimately, save more lives.