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Scientists seek to take the sting out of killer jellyfish

Box jellyfish venom can be extremely deadly.

Box jellyfish venom can be extremely deadly.

The toxin-filled tentacles of box jellyfish have been stinging beach-swimmers along the coast of northern Australia for decades. Now, scientists have described how their potentially lethal venom attacks cells and can stop the heart.

The team have also discovered that a specific form of zinc can slow the venom's damaging effect in mice.

"For over 60 years researchers have sought to understand the horrifying speed and potency of the venom of the Australian box jellyfish, arguably the most venomous animal in the world," said Angel Yanagihara, the study's lead researcher from the University of Hawaii.

Scientists have struggled to extract pure venom samples to study, but Dr Yanagihara was able to isolate levels of the toxin similar to those ejected from the animal in the wild.

When the toxin was mixed with both human red blood cells in test tubes, and injected into mice, the venom quickly punctured the cells, which caused a spike in potassium ions leaching into the blood's plasma.

"When that happens to a massive number of red blood cells, the amount of potassium [in the plasma] can reach lethal limits," she said.

Too much potassium in the blood interrupts the delicate balance of ions surrounding the heart's muscle cells, and can cause the cells, and the entire heart, to stop beating.

Dr Yanagihara believes it is this surge of potassium into the blood that makes box jellyfish venom so lethal.

When a group of mice were injected with a benign zinc compound, zinc gluconate, after envenomation they survived twice as long as non-treated mice.

"The administration of zinc either in the test-tube to human blood or in mice prohibits and delays onset of the rise in potassium," said Dr Yanagihara, whose findings are published in the journal PLoS One.

As a rise in potassium did not cause permanent damage to the heart, zinc treatment could give doctors time to give a patient cardiac support and administer drugs to remove excess potassium, she said.

Dr Yanagihara is now measuring the venom's toxicity, and the efficacy of zinc gluconate, in piglets.

The director of the Australian Venom Research Unit at the University of Melbourne, Ken Winkel, said the study was valuable because it demonstrated zinc gluconate could block the effects of the venom in mice, but it did not conclusively show how box jellyfish venom killed mice or humans.

Previous studies have found a high dose of the venom kills mice by destroying their heart tissue, but Professor Yanagihara's study did not investigate this.

While the study found mice released high levels of potassium after envenomation, such levels had not been observed in stung patients, he said.

There was a role for drugs and antivenom, but they were of limited use to a person who was in cardiac arrest on the beach, Dr Winkel said.

"Prevention of stings is the utmost importance," he said.

Box jellyfish can be found in the shallow coastal waters of Western Australia, the Northern Territory and northern Queensland. They are most prevalent during the wet season, but can be encountered on those coastlines year-round.

The animals' territory appears to be expanding as oceans warm and ocean currents change.

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