Many venomous snakebites carry no venom at all, by the snake's choice
Venom is costly to make, so snakes ration it. A bite on something far too big to eat is often a dry bite with no venom injected, a habit called venom metering. Around 80 percent of sea snake bites are dry, against about 25 percent for pit vipers, and rattlesnakes can adjust how much they deliver.
Snakebite is a far bigger global problem than most people in wealthy countries realise. The World Health Organization estimates 4.5 to 5.4 million people are bitten each year, with 40 to 50 percent developing some illness and between 80,000 and 130,000 dying. In 2017 it added snakebite envenomation to its list of neglected tropical diseases, aiming to spur research and make antivenom easier to obtain. Bites cluster in rural Africa, Asia and Latin America, among farmers, hunters and fishers who step on or near a hidden snake.
The contrast with rich countries is stark. Americans suffer some seven to eight thousand venomous bites annually, roughly one person in every 40,000, yet only about five of them die. Up to 95 percent of American snakebite deaths are blamed on the western and eastern diamondback rattlesnakes, and in the US and Europe bites happen most often to people who keep snakes as pets. The notion that a rattlesnake always rattles a warning first is a comfortable fiction; frequently the bite is the first sign one is nearby.
Venoms differ widely between species, which is why antivenoms often have to be matched to particular snakes and why the species responsible frequently cannot be identified. Elapids such as cobras, kraits and mambas mainly carry nerve toxins that can impair speech and breathing, while most vipers disrupt blood clotting. Some dangerous bites barely hurt, including those of kraits and coral snakes. Snakes of the family Atractaspididae in Africa and the Middle East can swing a fang sideways and stab without opening their mouths.
Several folk remedies do more harm than good. Sucking out venom, cutting the wound or applying a tourniquet are not recommended; washing the bite and keeping the limb still are. Antivenom is effective at preventing death, though it often has side effects, can be expensive and does little for damage around the bite. Overwhelming fear is the most common first symptom of any bite, and many survivors later experience depression or post-traumatic stress.
Source: Snakebite
