Deaths from snakebites are on the rise, recent evidence showing that hundreds of thousands of individuals across the globe every year are dying as a result of encounters with cobras, vipers or kraits.
It's estimated a resurgence of snakebites in Africa and Asia could soon account for a quarter of a million deaths every year. In the past, deaths from snakebites have been poorly reported and the extent of the crisis underestimated.
However, doctors in India recently carried out a detailed survey and discovered around 46,000 people in the country were killed by snakebites every year. Official statistics suggested the figure was only 1000. Similarly in Bangladesh, a detailed survey revealed the annual snakebite death toll there was about 6000.
"These two sets of figures are significant, for they suggest the estimate made by a World Health Organisation-sponsored study that snakes kill around 100,000 people a year across the globe may be a serious underestimate," said Oxford University tropical medicine specialist Professor David Warrell. "We now know more than 50,000 men, women and children die in India and Bangladesh from snakebites each year, and that figure is coming from just two nations.
"We also know that countries such as the Democratic Republic of Congo have enormous numbers of venomous snakes but provide no reliable data of any kind about snakebite deaths within their borders. So I would say it's more likely 200,000 or possibly more deaths a year are caused by snakes across the globe."
In developing countries struggling to cope with HIV, malaria, tuberculosis and other diseases the problem of increasing snakebites is particularly unwelcome.
"Many nations have no real knowledge of how bad the problem is within their borders," added Warrell. This is backed by the United Nations, which has described snakebites as "a neglected threat to public health".
The death rate isn't the only problem. Many people survive bites but often at a terrible price. "Victims, who are often agricultural workers, lose legs or arms or fingers and can't hold down their jobs. Children's limbs become gangrenous after being bitten by snakes and have to be amputated. They are blighted for life as a result. Girls have their marriage prospects ruined. The price of surviving a snakebite is often terrible."
Lorenzo Savioli, a former director of WHO's department for the control of neglected tropical diseases, said: "Snakebites cause severe disability, bring misery to families and kill thousands. We need to act effectively to control the problem."
Dealing with snakebites will grow harder in the next few years, because existing stocks of the important anti-venom Fav-Afrique, made by UK-based Sanofi Pasteur, expire in June. The company stopped producing the anti-venom last year. "We're now facing a real crisis," said Gabriel Alcoba of Doctors Without Borders.
Pharmaceutical companies in South Africa, India, Mexico and Costa Rica are working on replacement anti-venoms, but these have yet to be tested or marketed and may take years to be ready for wide use.
Scientists say a handful of species are the main culprits for soaring snakebite deaths in the developing world. These include carpet vipers, spitting cobras and puff adders in Africa and spectacled cobras, common kraits, Russell's vipers and saw-scaled vipers in India and Southeast Asia. In most cases the creatures kill by injecting a toxin that either causes serious internal bleeding or paralysis.
When they bite their natural prey - rats or mice, for example - this kills them almost instantly. Larger humans can take much longer to succumb. But as veins and arteries leak, and serious internal bleeding takes place, death can come in days.
But these aren't necessarily the world's most venomous snakes. The black mamba's venom is more toxic than the carpet viper's, for example, but the mamba rarely comes into contact within humans. By contrast, the carpet viper is often found in fields and undergrowth.
"Farm workers stand on them or startle them and get bitten," said Warrell. "Obviously, anti-venom is a crucial part of any treatment. But just acknowledging the problem and its extent would be a major breakthrough. Simple preventive measures could be introduced. Providing [bare-footed] farm workers with boots would be an enormous help."
46,000 people in India die from snakebites annually.
6000 die of bites each year in Bangladesh.