Wrong Antivenoms Are Costing Lives And Limbs

Saw-scaled vipers are probably responsible for many of the 100,000 annual deaths from snake bites. Tom Charlton

Snakebite is the most neglected of all under-resourced health challenges, according to the authors of a study of some of the most important antivenoms. As a result, enormous numbers of people are dying or suffering permanent disability from bites that could be treated with modest investments in manufacturing and distribution of antivenom.

Several studies estimate the number of annual snakebite deaths at up to 100,000, mostly in Africa and India. The figure hides the severe consequences for the much larger number who survive. Many lose limbs or have one or both kidneys cease functioning, with devastating effects on them and their families in largely agricultural economies.

Possibly the most frequent offenders are members of the Echis genus, which Dr Bryan Fry of the University of Queensland described to IFLScience as “the venomous equivalent of a landmine” for the way they hide in farmlands and their lethal ability to envenom their target. Better known as saw-scaled vipers, the genus has at least nine species. Antidotes exist and two are widely distributed, but their effectiveness against different Echis species had not been tested prior to a study now published in Toxicology Letters.

The paper reveals that the two most popular antivenoms, both of which were developed for use against Indian vipers, are not very effective at neutralizing the venom of most African snakes. Indeed, they don’t work all that well even against some closely related species to the original targets native to different parts of India.

With no antivenom at all, up to 20 percent of envenomation victims die, and inappropriate antivenoms only help a little. Yet Fry told IFLScience that two African antivenoms were effective against east and west African snakes respectively. Unfortunately, however, it is more expensive than the Indian alternatives, and therefore seldom stocked.

Fry and his co-authors argue that the problems are exacerbated by flaws in the World Health Organization’s standards for testing antivenom suitability. In some cases, antivenoms appeared somewhat effective on the standard test, but failed when the authors applied what they consider a methodology more closely replicating real-world conditions.

Distributing snake antivenoms in rural areas where medical facilities are few and far between is certainly a challenge, but Fry argues it still gives “better bang for buck” than almost any other tropical disease project. African and Indian venoms usually take long enough to kill their victim that many people make it to local hospitals, even with limited transportation options. However, this does little good when suitable antivenoms are unavailable. Subsidizing the appropriate antivenoms would not only save thousands of lives, but prevent many of the 1-5 million annual snake bite victims from having a limb amputated or kidneys fail, allowing them to keep earning a living.

The large eyes are one of the reasons saw-scaled vipers are "venomous equivalents of landmines," enabling them to see their targets well enough to reliably deliver deadly bites. Tom Charlton

 

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