Working out whether a snake has delivered venom with its bite may one day be determined by a simple blood test, new Australian research suggests.

The discovery could dramatically improve snakebite treatment in tropical rural areas, particularly in the developing world, where snakebite is a major health issue.

The work, previously published in Nature Scientific Reports, was presented this week at the Australian Society for Medical Research Annual Scientific Meeting in Sydney.

Senior author Dr Geoffrey Isbister, at the University of Newcastle's School of Medicine and Public Health, says the delivery of snakebite antivenom is often delayed until symptoms appear. This can sometimes be too late.

"The important thing is to be able to give the right patients antivenom early," says Isbister. "We need to identify in the first few hours if we've got envenomation."

"At the moment that is based on whether the patient feels a bit sick; but you also feel like that when you've just been confronted by a snake."

Isbister says once signs of paralysis and muscle damage begin to appear, it cannot be reversed by antivenom.

"Everyone thinks [antivenom] is this magic thing, but it doesn't reverse most things that have happened," he says.

"You've got to get the antivenom into the circulation early to bind to the snake toxins before they get to the muscles, before they get to the nerves and do the damage."

The scale of the snakebite problem is large with the World Health Organisation recognising it about four years ago as a tropical disease.

Isbister says there are one to two million cases of snake envenomation, with a potential fatality rate of 100,000 deaths worldwide.

Snakebite treatment is hampered by the availability of antivenom; high reaction rates to antivenom; and difficulties in diagnosing envenomation to allow early antivenom treatment.

Isbister says the development of a cheap diagnostic test for envenomation that can be done at the bedside is critical in addressing these issues.

Cheap detection tool

For this latest study his team, including Dr Margaret O'Leary at the University of Newcastle and Dr Kalana Maduwage from University of Peradeniya, Sri Lanka, focused on a common enzyme in snake venoms - phospholipase A2 (PLA2).

Using samples from confirmed snakebite patients in Sri Lanka and Australia they checked to see if PLA2 could be detected in the blood.

Pre-antivenom samples were collected from venomous bites from samples collected from Russell's viper, hump-nosed pit viper, Indian cobra, Indian krait and five red-bellied black snake were included in the study. These were compared with PLA2 levels in a group of un-envenomated patients.

Isbister says the levels of PLA2 were elevated in all those who had been bitten and injected with venom.

He says confirmation of envenomation means only patients who require antivenom will receive it.

"Even in a health clinic in Africa if you have antivenom then this test would help guide whether to give it rather than travelling eight hours to a hospital where it would be too late," he says.

Bringing it to the bedside

This can also have major financial implications even in developed countries such as Australia where antivenom is available at more than 90 per cent of hospitals, Isbister adds.

He says while thousands of cases of "snakebites" would appear at hospitals, only about five to 10 per cent would have envenomation.

"What comes into hospital is a suspected snakebite," he says adding this can range from being "attacked" by a stick, a bite by a non-venomous snake, to an attack from a venomous snake that didn't cause any effects.

Isbister warns against too much excitement as the analysis for this study involved expensive laboratory testing.

However, he says the "proof of concept" findings make it now feasible to begin research on development of a cheap testing kit.

"The actual test itself is not too complicated," he says, "it's working out a way you can do that simply at the bedside." http://www.abc.net.au/science/articles/2014/06/05/4018712.htm

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