Antivenom of the tiger snake may not be as useful as previously believed

Aug 2 2004

The simple life of sea snakes has given them a unique bite which could have major medical implications, while the antivenom of the tiger snake may not be as useful as previously believed, an Australian study has found.

Deputy Director of the University of Melbourne’s Australian Venom Research Unit, Dr. Bryan Fry, said the study found big differences in the effectiveness of two different types of antivenom currently used for the treatment of sea snake bites.

Recently published in the journal Toxicon, the researchers from the University of Melbourne and Monash University tested the antivenoms of the sea snake and tiger snake against the venoms of a wide variety of sea snakes and sea kraits.

Dr. Fry says, “The sea snake antivenom worked brilliantly, but the tiger snake antivenom was clinically useless and could not neutralise the deadly sea snake venom. This has big implications because tiger snake antivenom is currently recommended for the treatment of sea snake bites if the sea snake antivenom is not available.”

“This means that a person given tiger snake antivenom to treat a bite might die or have severe long term damage when they probably would have survived if given sea snake antivenom.”

The only commercially available sea snake antivenom in the world is made by CSL in Melbourne, using a formula first developed almost half a century ago. It is made using the venom of a single species of sea snake – the beaked sea snake – chosen because it is responsible for 90% of deaths from sea snake bites.

Dr. Fry dived all over the Great Barrier Reef and in tropical waters off the coasts of Bali, Malaysia and the remote Ashmore Reef near West Timor to collect the venoms for the study, which was funded by the Australia & Pacific Science Foundation.

He found that the antivenom worked remarkably well against a wide range of venoms, not just from different varieties of sea snake, but also from venom of the very unrelated sea kraits.

“The true sea snakes are simple little Australian snakes that spent a day at the beach and never came home. The sea kraits however have a much murkier past and are a much older independent marine split from the land snakes,” Dr. Fry says.

It is highly unusual for the antivenom from a single species to be so effective across such a wide array of snakes and it has never been seen in the land snakes, even between closely related groups of snakes, he says.

“For example, the taipans and brown snakes are very closely related land snakes and have very similar venoms, but they have each specialised so much that they need different antivenoms. The taipan antivenom is not effective for treating brown snake bites and vice versa.”

“In contrast, the sea snakes have diversified into a myriad strange and wonderful forms but the venom seems to have stayed the same and is remarkably streamlined in comparison to the land snakes.”

Dr. Fry believes that the simplicity of the sea snake venom is most likely due to the simple life the sea snakes lead. He says that unlike land snakes which feed on many different animals, sea snakes feed on nothing but fish and eels.

Their venom is simple because their diet is simple, and this makes it easier when developing antivenom for treating against snake bites, he says.

“This very simplicity is why the antivenom works so well against all of the sea snakes even though it is made using the venom of only one of them.”