Brown snake venom even more deadly with age

By Angela Heathcote May 19, 2017
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The venom of Australia’s deadliest snake attacks prey differently according to the age of the snake – with potential implications for the way we treat bites, a new study has found.

RESEARCHERS AT THE University of Queensland have discovered the venom of brown snakes becomes even more potent with age, with adult and baby snake venom containing different toxins to kill prey.

By studying the life cycle of Australia’s deadliest snake (Pseudonaja sp.), the scientists were able to confirm that the diet of young brown snakes (which eat small reptiles) compared to older snakes (which can eat larger mammals) has resulted in a variation of toxins within the snake’s venom.

They found that while the venom of younger brown snakes attacks the nervous system, the venom of older brown snakes coagulates the blood.

“Parallel to the specialisation for particular prey items, there was a specialisation for particular toxins,” explained molecular biologist Bryan Fry from UQ’s School of Biological Sciences’ Venom Evolution Laboratory.

“Baby brown snake venom is neurotoxic while adult venoms hit the blood coagulation,” added Bryan, who led the study.

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Around half of all human deaths by snake bite in Australia are caused by the venom of the brown snake. (Image: Stewart Macdonald)

Previously it was understood that the snakes’ venom killed prey by inducing catastrophic strokes, however the new research has revealed this function is far more complex.

After captive breeding young brown snakes and extracting venom from the parents, researchers discovered the presence of neurotoxins in baby brown snake venom cause their lizard prey to go limp and stop breathing.

Around half of all human deaths by snake bite in Australia are caused by the venom of the brown snake. Bryan explained that while the venom could not cause an instant stroke in humans as it does in smaller mammals, victims could still die from internal bleeding.

The findings could mean snake bite treatments may need to vary according to the age of the brown snake, said Bryan. “We are investigating how well the anti-venom works against the neurotoxic effects of the baby venom. The anti-venom is made to neutralise the blood effects of the adults. However, the adults still contain low levels of the neurotoxins so there is a chance the anti-venom may in fact cross-react,” he said.

However Professor Geoff Isbister – a venom expert from the University of Newcastle, who wasn’t involved in the study – said he thinks it’s an exaggeration to suggest the findings could impact our approach to treating brown snake bites.

“The study simply shows that there are differences in the effect of brown snake venoms on enzymes involved in the clotting pathway. Different species of brown snakes have different effects and these venom effects appear to change as the snakes mature,” he said.

Bryan added that until current brown snake antivenom is tested with baby snake venom, it’s important to consider the potential need for a “plan B treatment”.

The research was published in the journal Comparative Biochemistry and Physiology.