Australian stinging trees contain ‘scorpion-like venom’

BRISBANE • Australia is notorious for its venomous spiders, snakes and sea creatures, but researchers have now identified “scorpion-like” toxins secreted by a tree that can cause excruciating pain for weeks.

Split-second contact with the dendrocnide tree, a rainforest nettle known by its indigenous name gympie-gympie, delivers a sting far more potent than similar plants found in the US or Europe.

The tree, which has broad oval- or heart-shaped leaves, is primarily found in rainforest areas of northeast Queensland, where it is notorious among hikers.

A team of Australian scientists said they now better understand why the gympie-gympie’s sting haunts those unlucky enough to brush up against its leaves.

Victims report an initial sting that “feels like fire at first, then subsides over hours to a pain reminiscent of having the affected body part caught in a slammed car door”, the University of Queens- land researchers said yesterday.

In the final, drawn-out stages, simply taking a shower can reignite the pain.

Though the gympie-gympie is covered in fine needle-like hairs similar to other nettles, previous testing for common irritants such as histamines came up empty.

Irina Vetter, an associate professor at the University of Queen- land’s Institute for Molecular Bioscience, said the research team discovered a new class of neurotoxin mini proteins, which they christened “gympietides”.

“Although they come from a plant, the gympietides are similar to spider and cone snail toxins in the way they fold into their 3D molecular structures and target the same pain receptors — this arguably makes the gympie- gympie tree a truly ‘venomous’ plant,” she said.

Australia is already infamous for its venomous fauna including snakes, box jellyfish, blue-ringed octopus and funnel-web spiders, although deaths in humans from bites or stings are rare.

Vetter said the long-lasting pain inflicted by the tree might be explained by the gympie-tides permanently altering the chemical makeup of the affected sensory neurons — not due to the fine hairs being stuck in the skin.

The scientists hope their research, published in the peer-reviewed journal Science Advances, will eventually help lead to better pain relief treatment for people who have been stung. — AFP