Screen test

If you get bitten seriously by a snake the best thing is to get the antivenom into you as quickly as possible," says Professor Alan Harvey, at the University of Strathclyde in Glasgow. In Nigeria, where the untreated bite of fairly common snakes such as the cobra (Naja) or the Echis and Bitis vipers can be fatal, speed is crucial.

Although antidotes for these three severe types of snakebite do exist, they are generally prepared by immunisation of horses. The animals produce antibodies against the venoms, which can be collected from their serum. The resulting concoctions are not particularly stable and need to be stored in a fridge, which is not always practical in a developing country. They also usually have to be injected intravenously, posing an added worry in areas with a high incidence of HIV/AIDS.

Moreover, these antidotes can only be administered in hospitals, which tend to be a long way from the rural populations most at risk from snakebite. "If it takes you two days to get the hospital you could be seriously ill or dead," says Professor Harvey, "but if you can get back to the village and knock on the door of the local healer, at least you take an antidote fairly soon after the bite."

But do the plant remedies used by these local healers actually work? Two years ago, Professor Harvey’s colleague, Professor Isaac Asuzu at the University of Nigeria in Enugu State, Nigeria, was awarded a Wellcome Trust Travelling Fellowship to analyse some of these traditional remedies scientifically. "The healers he interviewed seemed genuinely interested in what he was doing," explains Professor Harvey, "and gave him plant samples and information, albeit divulged under conditions of secrecy. They also expressed interest in getting feedback regarding his results."

Indeed, the main aim of the research is to identify which remedies work, to help the local healers select their treatments with greater accuracy. In addition, if remedies found to be successful contain some relatively simple chemicals that can be purified easily, the healers might also be given guidelines enabling them to make these preparations themselves.

Professor Asuzu brought samples from around ten plants to the University of Strathclyde in Glasgow, where the extracts were simplified to localize the chemical constituents responsible for the activity. "To start off with we make quite a crude extract, pretty much as the native healers would do, perhaps by making a herbal tea, straining it, and then looking at what’s in the solution," explains Professor Harvey.

Purified extracts were then tested on tissue cultures treated with the three dangerous Nigerian snake venoms (from the Naja, Echis and Bitis snakes), obtained from the Liverpool School of Tropical Medicine. "Four out of the ten look quite promising in terms of preventing or reversing some of the toxic effects of the snakebite," says Professor Harvey. They really did seem to have a beneficial effect, even when they were added after the venom had started to work."

Analytical techniques are now being used to isolate the molecules causing the activity with more precision. "We’re a couple of steps away from the final scientific answer, which is having a chemical structure that has a defined activity that we can understand," says Professor Harvey.

The next step, under a new three-year Wellcome Trust grant, will be to see whether the most concentrated or pure active ingredients will work in a live animal – whether it will reverse the effects of the venom in mice, for example. The new grant will enable Professor Asuzu to set up a tissue culture laboratory in his own department at the University of Nigeria. "The hope is that by the end of the period of the grant he’ll have quite a robust and self-contained lab," says Professor Harvey. "Then for the final stage chemical analysis of the structure of the active molecules, he’ll work with some of my colleagues here in Glasgow."

Under the new grant, Professor Asuzu also aims to look at additional plant remedies. So far, he has only talked to a handful of healers – a small drop in an ocean of traditional knowledge.

See also

• Spot the difference: Article describing research on the taxonomy of pit vipers through DNA analysis
• Going ballistic: Article describing the use of DNA immunisation to create cheap effective antivenoms

External links

• Strathclyde Institute for Drug Research: Research of Professor Alan Harvey at the University of Strathclyde