19 June 2009

Bitten by a mamba in the Dusi: What happens to the body?

What happens to your body when bitten by a mamba - or another snake - and why can it be lethal? Pic: Beeld

Dusi Canoe Marathon paddler Colin van Heerden appears to be recovering from a bite by a black mamba. What happens to your body when bitten by a mamba - or another snake - and why can it be lethal? Pic: Beeld

After two terrifying days involving a helicopter airlift, being put into a drug-induced coma and kept alive on ventilator, Dusi Canoe Marathon paddler Colin van Heerden appears to be recovering from a bite by a black mamba.

Van Heerden was bitten by the venomous snake while portaging a canoe with his paddling partner near the finish of the race.

Mamba's venom = neurotoxic
The snake that apparently bit Van Heerden belongs the mamba family, whose venom is neurotoxic. It paralyses the victim’s muscles by attacking the chemicals responsible for the operation of the nervous system.

It can be lethal when the intercostal muscles, helping the lungs to expand when you breath, are paralysed. It is very important to get a victim to a hospital and onto a ventilator as soon as possible to support his breathing.

The 4 types of snake venom in SA
“There are really four sorts on venomous snakes in Southern Africa, says Craig Smith, a spokesman for the Fitzimons Snake Park in Durban:

  • Neurotoxic: This venom attacks the neurochemicals transmitting neuro-signals from the nerves to the muscles. It leads to the paralysis of muscles, and breathing can become impaired. Snakes with neurotoxic venom include the black mamba, rinkhals, green mamba, and non-spitting cobras.
  • Cytotoxic venoms: This attacks the cell structure of the victim. “The venom causes necrosis, or the destruction of the tissue. It’s like a rotten banana - you might see a bite on the hand, which has a bit of swelling and a couple of black spots on it, but underneath, there’s tissue damage all the way up to the shoulder and even into the chest. It’s found in the large adders, such as puff adders and night adders.
  • Haemotoxic venom: This venom causes thinning of the blood, and can lead to excessive bleeding. “It can result in bleeding from the membranes such as the sinuses, ears, eyes and mouth. One drop of boomslang venom can kill 20 people – it’s super concentrated, but works very slowly.” The venom of the boomslang and the twig snake (also known as the vine snake or bird snake) – is haemotoxic.
  • Myotoxic venom, found in the yellow and black sea snakes. “Bites from sea snakes are fairly rare, as the snakes live in deep seas, but occasionally one will be washed into shallower waters if it’s sick, or by strong seas. “Myotoxic venom attacks the muscles, so the victim usually drowns. But if they make it to shore they usually survive,” Smith says.

Blind terror
Many people are terrified of snakes, but the truth is that snakes are generally timid and would rather flee than risk confrontation with humans. Despite our primordial terror of them, snakes also play a vital role in the food chain, controlling the rodent population.

Two types of antiserum
Most hospitals have two types of antiserum – one for boomslang venom and a broad-spectrum one for all other snake venom.

“Each person’s reaction to venom is different, just like individuals react differently to bee stings.

”Doctors usually treat these bites according to the symptoms: if the victim has trouble breathing they’ll be put in an oxygen tent, for instance. Doctors can usually identify the snake according to the victim’s symptoms and the geographic area where the bites took place. William Smook – Health24 writer



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