Brown snakes get more deadly with age

Discovery reveals baby brown snakes undergo venom transformation


A baby eastern brown snake with its stripes on display. Pic by  Stewart Macdonald.

A baby eastern brown snake with its stripes on display. Pic by Stewart Macdonald.

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Discovery reveals baby browns undergo venom transformation

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New research has revealed a stark difference between the venom of juvenile and adult brown snakes.

A previously unknown venom transformation was discovered when researchers at University of Queensland (UQ) decided to investigate how adult and juvenile brown snakes immobilise their prey.

The study, published in the journal of Comparative Biochemistry and Physiology showed the venom of young browns attacks the nervous system, while the venom of older snakes has dangerous effects on the circulatory system.

Babies have stripes, which they lose in maturity, becoming solid brown. The different colouration is an indicator of their different ecological niches.

Juvenile brown snakes eat lizards. Their venom attacks the nervous system, which can produce symptoms similar to the venom of a death adder.

Adult browns eat mammals. Their venom contains toxins that cause devastating interference with blood clotting, which immobilises rodent prey, causing them to have a stroke.

Even though the venom is diluted by the larger blood volume of a human and do not cause stroke, bite victims can still die from internal bleeding.

The study compared venom from snakes just out of the egg with that of their parents, but the time of transition was not pinpointed.

Lead researcher Associate Professor Bryan Fry, UQ School of Biological Sciences, said brown snake venom was shown to act upon the blood in a “much more complex way” than was previously known.

It was known that brown snakes, like taipans, convert a protein called prothrombin into thrombin, which causes blood clots, which lead to stroke.

“However, the speed of action could not be accounted for based on this action alone,” Dr Fry said.

“Our team discovered brown snakes are potent in activating Factor VII, another blood clotting enzyme, which is the missing element of brown snake envenomations.

“The feedback loop created by this enzyme would become a venomous vortex and dramatically accelerate the effects upon the blood.”

More work is needed to determine if juvenile brown snake bites produce different symptoms.

Further studies will be launched to determine what age the snakes are when their venom changes, and if the venom changes at the same time as the snakes loses its stripes.

The discovery also opens new avenues of investigation for snake bite treatment as well as for drug development, where snake venom can play a key role.

Brown snakes are Australia’s deadliest snake. They possess one of the fastest acting venoms in the world, with a 15 to 20 minute kill time.

But not only is it deadly, its symptoms are elusive.

“One minute, after a bite, you’ll be feeling alright. And then within five minutes, you can be dead,” Dr Fry said.

But as Dr Fry points out, “there is no snake bite problem in Australia”, at least not compared to most other countries.

Of the few hundred snake bites in Australia each year, there are typically 4 to 6 deaths.

In India, there are one million bites each year and about 100,000 deaths.

And even though juvenile browns venom is now known to differ from adult snakes, “that certainly doesn’t mean we are saying the babies aren't dangerous”, Dr Fry said.

“Any snake bite is potentially life threatening, so you should always go to hospital, and stay overnight.”

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