The black-necked spitting cobra lives mainly in sub-Saharan Africa.
Luca Boldrini (CC BY-SA)
A commonly used blood-thinning drug could prevent hundreds of thousands of people bitten by cobras from having to have limbs amputated.
Snakebites kill 138,000 people each year, mostly in sub-Saharan Africa, South Asia and Southeast Asia, and a further 400,000 suffer complications such as tissue death and subsequent amputations.
Focusing on complications from cobra bites, Tian Du and his team from the University of Sydney in Australia found that cobra venom targets a molecule called heparan sulfate that coats the surfaces of cells at the bite site, and a natural substance called heparin produced by certain immune cells.
The researchers then exposed human skin and blood cells to the venom of two African cobra species: the red cobra (Naja Parida And the Black-necked Spitting Cobra (Naja NigricolisAdding heparin, a commonly administered blood-thinning drug, prevented the toxin from killing the cells.
Similar studies in mice also reduced the risk of tissue death, in which heparin “was able to almost completely prevent localized damage at the bite site,” says Greg Neely, another member of the research team at the University of Sydney.
Scientists believe that while the treatment may be effective against bites from many different types of cobras, it probably won’t work on other species, unless their venom uses a similar chemical pathway to destroy cells.
Unlike existing antitoxins, heparin is stable at room temperature, which could make it easier to access when quick treatment is needed, which could be done via an auto-injector such as an EpiPen, Du said.
Another advantage of heparin is that existing antivenoms don’t prevent necrosis, Du says, but Jeff Isbister of the University of Newcastle in Australia says that’s probably because antivenoms aren’t commonly available so soon after a snakebite.
“The paper didn’t compare it to antivenom, because that’s probably just as effective,” Isbister says. The mice were given heparin immediately, which may have helped, he says. “But would heparin still work after an hour, four hours or 24 hours it takes to get from remote areas of Tanzania to someone who’s been bitten by a cobra?”
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