The blood sucking bite of the vampire bat is being harnessed for medicine.

A substance secreted by the bat to keep blood flowing shows promise in treating stroke.

Scientists in Australia say animal tests show it can dissolve blood clots in the brain.

This is fascinating research and holds great potential The Stroke Association

Clinical trials on human patients are being carried out in Europe, Asia and Australia.

The enzyme was originally extracted from the saliva of the vampire bat.

It is known as Desmodus rotundus salivary plasminogen activator, or DSPA, after the bat's scientific name.

"When the vampire bat bites its victim, it secretes this powerful clot-dissolving (fibrinolytic) substance so that the victim's blood will keep flowing, allowing the bat to feed," said co-researcher Robert Metcalf from the Monash University Department of Medicine in Victoria.

Clot buster

The substance is similar to tissue plasminogen activator, a clot-busting drug used to treat heart attack or stroke patients in some countries.

The drug can dissolve blood clots, which cause most heart attacks and strokes.

A bat version of the clot-busting drug could have added advantages.

Tests on mice suggest it might be safe to use up to nine hours after the onset of a stroke because there is a lower risk of brain damage.

Tissue plasminogen activator is administered to human patients up to three hours after the onset of stroke.

It cannot be used after this time because there is a risk of brain damage.

The study was carried out by injecting the bat substance and the conventional treatment into the brains of mice and tracking the survival of brain cells.

DPSA may be safe for longer, according to the animal tests, which are reported in the journal Stroke: Journal of the American Heart Association.

'Great potential'

However further research is needed, said Larry Goldstein, chairperson of the American Stroke Association Advisory Committee.

"It needs to be understood that this study is limited to mice without stroke and focused only on toxicity," he said.

"Whether this approach will prove either safe or efficacious in improving stroke outcomes requires further testing."

The comment was echoed by the UK research charity, The Stroke Association.

Director Eoin Redahan told BBC News Online: "This is fascinating research and holds great potential.

"About 80% of all strokes in the UK are caused by blood clots and so the bat saliva could be very important."