Rapid tests could take the sting out of snakebites

Knowing which snake bit a person could save their life Copyright: DA Warrell

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Tests that show quickly whether someone has been injected with venom following a snakebite could help save lives and money by allowing healthcare workers to give the right antivenom rapidly and only to those who need it, according to researchers.

Several such tests for deadly snake species are now in development, the American Society of Tropical Medicine and Hygiene’s annual meeting heard this week (4–8 December).

There are 100,000 deaths from snakebites each year, according to WHO estimates, but there could be many more that go unrecorded.

A recent study in PLoS Neglected Tropical Diseases has found that there are 46,000 snakebite fatalities a year in India, much more than the official figure of 2,000.

Swift identification of the venom of certain species, such as the krait, could save lives because it contains a neurotoxin that irreversibly destroys nerve endings. Normally, doctors wait for symptoms before choosing an antivenom, but for a krait bite victim this could mean paralysis or death.

But, as up to 90 per cent of snakebites are non-venomous or from snakes that do not inject venom, a rapid diagnostic kit could help identify whether someone needs antivenom. This could not only cut risks from adverse reactions to antivenom, but also cut waste — antidotes are expensive, at around US$70 a dose.

"The diagnostic tests will help physicians to make faster and more reliable judgements on whether or not to give antivenom and which antivenom to give to their patients," Ulrich Kuch, head of the Emerging and Neglected Tropical Diseases Unit at the Biodiversity and Climate Research Centre in Germany and the leader of the research to develop the tests, told SciDev.Net.

The tests use a blood dipstick test similar to that used for pregnancy tests or the rapid diagnosis of malaria. Kuch is developing the tests with a German biotechnology company, Miprolab.

A specific antivenom to match a species can be essential. "If someone is bitten by a cobra, you need to give an antivenom for cobra to cure that person," Kuch said.

A prototype to detect venom from Russell’s viper will be trialled next year in Myanmar (Burma), where the snake is the 12th most common cause of death. It was developed through research collaboration between researchers in Myanmar and Germany. An aim is to allow the government of Myanmar to make the tests under an open-source agreement, for roll-outs in the region. A test for krait bites for use in South Asia is in pre-clinical stages.

"These tests can be modified for a species simply by changing the antibodies that detect different snake antigens. There is a great opportunity to make test kits for different regions," Kuch told SciDev.Net.

David Warrell, emeritus professor of tropical medicine at the University of Oxford, told SciDev.Net there are also ‘broad-spectrum’ antivenoms that cover species in an area. But he added: "Knowledge of a particular species could help predict the course of envenoming, reducing the risk of complications".

Warrell said he was concerned about the cost of tests. "For clinical use in a developing country, price is critical," he said, but added that "there is an opportunity to make them simple and less expensive".

Kuch said tests would cost no more than the standard rapid diagnostic test for malaria, about 40 cents (US) each.

Link to study in PLoS Neglected Tropical Diseases [644kB]

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