What Are Antivenoms, Why Are They Needed, Why Are They Scarce, and What's Being Done to Ensure That They Are Available to all Snakebite Victims?
Where are poisonous snakes located and what kind of threat do they pose?
Poisonous snakes are present in all but a few countries, but they are particularly concentrated in the tropical regions. In the U.S., many venomous snakes are found in the extreme south, from Florida to Southern California, but they are most abundant in the southwestern states.
In total, there are an estimated 600 different species of poisonous snakes in the world. More than 100,000 people die and more than 300,000 people lose a limb or are inflicted with another severe injury as a result of being bitten by a venomous snake.
Who is most likely to die or suffer severe injury due to a bite from a poisonous snake?
People, particularly those who work outdoors (e.g., farmers), in underdeveloped regions of the world (mainly in Africa and southern Asia) are most susceptible to injury or death from a snakebite, as such individuals are likely to reside in rural areas in which health care is lacking and medical facilities are deficient in resources. Women and children typically are more susceptible to death or injury caused by a snakebite than are men as they generally have a smaller body mass than do men.
What are antivenoms and why are they needed?
What are antivenoms? Antivenom consists of immunoglobulins that are naturally produced by a host animal, such as a horse, goat or rabbit, for example, whenever the host is exposed to venom. To obtain antivenom, scientists inject a small amount of venom into a host and then collect the antivenom immunoglobulins from the host’s blood. In many cases, the only way to effectively treat a human that has been bitten by a poisonous snake is to inject that person with antivenom. Failure to do so makes it increasingly likely that the venom will prove fatal or extremely harmful.
Why is antivenom not universally and abundantly available?
There are more than 600 snake species in the world. In general, each batch of antivenom is specific to venom from only one species of snake. That means that antivenom produced in a host that has been injected with, for example, rattlesnake venom, is useful for treating rattlesnake bite victims, but is useless for treating, for example, cobra or copperhead bite victims. In order to protect the world’s population against a bite from any species of snake, more than 600 “species” of antivenom therefore would need to be generated.
Companies are not interested in producing antivenoms, however, because they are not profitable products. This is true because they are expensive and difficult to generate and because many snakebite victims do not have the financial ability to bear the cost of treatment. Other groups therefore will need to step up to make sure that antivenoms are produced and made available to all snakebite victims.
What is the World Health Organization doing to increase the availability of antivenoms?
The World Health Organization (WHO) has publicly recognized the need for alternative means for generating anitvenoms and making these drugs readily available to snakebite victims worldwide, and the WHO is beginning to take steps toward achieving this goal. For example, the WHO has prioritized which species-specific antivenoms are most urgently needed. More specifically, the WHO has placed each species of poisonous snake into one of two categories. Category 1 snakes are those that are most widespread, greatest in number, and most likely to cause death or severe injury. The WHO considers production and distribution of antivenom from Category 1 snakes to be of highest medical importance.
Category 2 snakes, while still dangerous and capable of causing death or disability, are thought by the WHO to be of secondary medical importance for various reasons, including that these snakes are found in reduced numbers and in limited or remote locations, for example. This categorization effort is helpful because, until now, such data regarding poisonous snake distribution and level of threat has been sparse and difficult to interpret.
The WHO also has created an online database that describes the worldwide distribution of poisonous snakes and their available antivenoms. In the past, this information was not known, was hard to find or was ambiguous.
It is hoped by the WHO that these new resources will assist government health agencies, public health officials and health care professionals in various countries to formulate and carry out a plan for large-scale production of antivenoms that are most needed in their particular country. If the WHO is successful in reaching it’s goal, there won’t be anyone asking “what are antivenoms” or “why aren’t they available”.
S. Hutson, Antivenoms needed, say officials, but companies won’t bite, Nature Medicine, 16:615 (2010).
World Health Organization, Venomous snake distribution and species categories: https://apps.who.int/bloodproducts/snakeantivenoms/database/
World Health Organization, WHO highlights critical need for life-saving antivenoms: https://www.who.int/mediacentre/news/notes/2010/antivenoms_20100504/en/index.html