Snakebites kill up to 94,000 people worldwide every year, with the highest number of deaths in South Asia and sub-Saharan Africa.
The main obstacle to saving lives is the global availability of antivenom. Until fairly recently, the gold standard has been a targeted antivenom that works against a specific species of snake. But that means doctors must know exactly which snake out of around 600 possible species did the deed, and that makes individual antivenoms costly to stock.
In Africa, the most effective treatment has been a multipurpose antivenom that works against a variety of vipers and cobras found on the continent. But according to current reports, stockpiles of this antivenom are expected to run out in June 2016. The main supplier, a French pharmaceutical company, halted production because the antivenom was no longer profitable.
Now, scientists in Thailand have found a way to make a single antivenom that works against 18 species of snake found in Asia and Africa. The team maintains that their version will be more affordable and more widely useful, helping to bring antivenom to the resource-strapped regions that need it most.
Kavi Ratanabanangkoon, of the Chulabhorn Research Institute in Bangkok, already had plenty of firsthand experience with snake dangers.
“I have 15 dogs at my place. Sadly, five of them were killed by cobras,” he says. “Once in a while, a 1.5-metre cobra shows up in my garden. The problem is not too far away.”
To find a more universal antivenom, Ratanabanangkoon and his colleagues collected 12 venom samples from six species of Asian snakes, including four cobras and two kraits.
Some of the snakes, like the Malayan krait, were not easy to get, he adds. The team had to spread the word that they would pay a hundred dollars for a wild serpent. Once caught, a snake farm run by the Thai Red Cross cared for and milked the snakes on the team’s behalf.
In a commonly used procedure for making antivenom, the scientists injected nonlethal amounts of the venoms into horses and harvested the antibodies they produced.
But in a twist, the team first filtered out only the most lethal venom proteins for nine of the 12 samples. (For the other three, they didn’t have enough venom to filter.)
The theory was that using just the most important proteins would allow the horses to produce an effective antivenom even though they were injected with a potent brew of multiple toxins.
When the researchers gave the resulting serum to mice that had been injected with snake venom, all the rodents recovered, the scientists report this month in PLOS Neglected Tropical Diseases. Even better, the antivenom worked not only against the six species of snakes used in the study, but also against venoms from 12 related species.
Ratanabanangkoon was particularly surprised that their antivenom rescued mice from four African snakes from Egypt and Cameroon, perhaps because the snakes were also in the cobra family and presumably have similar toxins.
The team is hopeful that the method can eventually produce a multipurpose antivenom against all snakes in the cobra family found in Asia and Africa.
The number of antibodies generated in the experiment—a sign of the serum’s effectiveness—is respectable but not amazing compared to other antivenom efforts, says Leslie Boyer, director of the VIPER Institute at the University of Arizona. She also notes that the study is small, and that the researchers didn’t directly compare their results with more traditional single-species antivenoms.
But she says the study is a good proof-of-principle and an example of using less sexy and perhaps more practical approaches than the high-tech solution of trying to make synthetic antivenom.
“I like it, and from everything that I’ve heard, Asia is so desperately in need of ways to treat snakebites for rarer snakes in smaller countries. That would be a tremendous improvement in public health,” says Boyer, who adds that she hopes the Thai team gets more funding to do a larger controlled experiment. From there, the team would need to move on to trials in humans.
If their multipurpose antivenom does eventually hit the market, the team stresses that they intend to make it affordable and easily accessible.
“The process is so simple, and we do not patent it,” says Ratanabanangkoon.