Why is snake venom dangerous?

Radiolexicon: snake venom

Cologne, zoological garden, reptile house. It's warm and humid. Children run around, mothers push prams through the crowd. On the walls there are terrariums with lizards and spiders, frogs and snakes. Some students are standing in front of a glass box in which there is mostly green growth: no trace of animals. But they are there - and they are dangerous!

"This is the venomous snake section of the terrarium, you can easily see that, this facility is hermetically sealed, that is, in the unlikely event that an animal can escape, this facility is specially secured,"

which is a good thing - continues Thomas Ziegler from Cologne Zoo - because none of the snakes kept here are harmless.

"Here we also see a capital rattlesnake, Crotalus durissus, the dread rattlesnake, which is native to Central America. These rattlesnakes, like the native adder, like the vipers, are generally characterized by the fact that they have poisonous teeth that can be erected for a particularly long time Shut her mouth, she has to fold in her teeth, otherwise she would bite through her lower jaw. These rattlesnakes are known to have a haemotoxic poison, a poison that corrodes blood or tissue, which you can tell from the outside that it is a there is a dark discoloration of the bite site and there are blood blisters there and then the tissue is decomposed there. "

Anyone who hears this noise in the wild is in great danger! The dread rattlesnake bears its name for a reason. Nobody survives a bite without an antidote, sometimes death occurs after just a few minutes.

"All known ingredients of snake venom are by their chemical nature protein molecules, that is, large molecules, which we call proteins, ultimately have enzyme or fermentation activity which, for example, dissolve the tissue on the bite wound and thus spread the venom from the bite region transport into the body, they can also trigger digestive processes in the organism, for example by destroying cell membranes they cause the red blood cells to dissolve and the person is thus killed, "

says Stefan Herzig, Professor of Pharmacology at the University of Cologne. Zoologists have long speculated why certain snake poisons have a digestive function. Your answer: Often the victims of snakes are much bigger than they are. So it makes sense to initiate digestion outside the body - a method that, by the way, some spider species also use. Another phenomenon is interesting in this context: Many snakes have extremely strong poisons. The Australian inland taipan, for example, which a few milliliters is enough to kill its victim. In such cases, Herzig suspects, the snake compensates for non-existent fighting abilities with the super poison: What the muscles cannot do, the high-tech poison does!

Hearty: "A snake must bring its victim to a standstill as quickly and effectively as possible, whether through death or simple paralysis, because it does not keep up with the victim because it is not that fast, and this should be possible with a small amount of the Poison, and evolution has made sure that with the smallest possible amount of poison, the snake kills its victim. "

The digestive poisons only cover part of the horror spectrum. As a second variant, some types of snake use neurotoxins or nerve toxins.

Ziegler: "And there you sometimes don't see anything from the outside, except for the puncture or bite marks, you can see it in the bitten person by the fact that he can no longer move his eyelids, that he shows signs of paralysis or twitches, that saliva runs out and uncoordinated things happen . "

Cobras use this group of poisons, but also the feared African mambas. Some snake species - and this is particularly treacherous - could not, however, clearly decide on one or the other class of poison in the course of their development. Their poison therefore attacks both blood and tissue, but also affects the nerve tracts at the same time. Good for those who are bitten by false snakes in such cases, because the chances of survival are slightly higher.

Ziegler: "The snakes do not have their poisonous teeth in the front area, but they are relatively far back in the jaw, and so that there can be a poisonous effect when biting, this snake has to chew on the wound so that the back teeth can be used as a rule, an effect that is not so dangerous for humans, but there are also very dangerous animals. "

For example, African tree snakes, where the bite is usually fatal for humans - unless they are given an antidote or a serum. Because this is rarely available immediately, first aid must first be used. Stefan Herzig, pharmacologist at the University of Cologne:

"An initial measure in the extremities, legs or arms is to tie off the associated body parts to the point that the blood flow is blocked, but the blood flow is not yet completely cut off, so a pulse should still be present. This prevents the poison from flowing out too quickly and creates time for further detoxification measures. "

Under no circumstances should the bite wound be sucked out - even if this is part of the standard therapy in many films! Otherwise, the poison gets into the head area via micro-injuries. Cutting open the wound yourself - also a popular treatment method - is also not advisable: the wound becomes larger and only gives the poison further routes into the body. Incidentally, whether it is fatal or not depends on several factors.

Ziegler: "It depends on the constitution and on the organism, whether it is an adult human, and the snake can decide for itself how much poison it injects, because the snake also needs the poison to decompose the prey from the inside, And in this respect, such a poison bite for a snake is also a very high cost, it has to regenerate it and then cannot take in or digest any food for the next few days, and in this respect it will be careful with its poison, especially its resources good to deal with. "

If there is a bite, only one thing helps: a serum has to be found, and quickly.

Hearty: "For serums we need the so-called snake farms, which means that the snakes that are important for a certain region are kept, their poison is milked and small amounts are used to immunize animals, usually horses. These horses receive and in this way An immunological defense against the snake venom and serum is obtained from their blood, which is then effective against all snake species common in a certain region, let's say Central Europe. "

Snake sera are complex and expensive to produce. Scientists have long been looking for simpler methods of producing antidotes. Researchers at the Liverpool School of Tropical Medicine proposed a new procedure a year ago. Instead of the snake's original venom, they use some kind of artificial DNA. The genome represents the cross-section of the genetic information that is important for the venom production of a certain snake species - in this case the African sand-rattle otter. The researchers injected the artificial DNA into mice and were able to use the animals' blood to produce a snake serum that proved to be much more effective than conventional antidotes. But there is one point where the researchers are still standing still: the antidote must be injected in any case, treatment per os - i.e. as an orally administered tablet - is not possible.

Hearty: "Snake venom is administered parenterally, i.e. through an intramuscular injection, so the snake can afford to use substances as poison that are immediately destroyed when ingested through the digestive tract, are not absorbed in the first place, and cannot have any effect at all. "

The possibility of using highly poisonous snake venom in tiny doses as a therapeutic agent is always discussed. No drug based on snake venom is officially approved in Germany. However, some centers for naturopathic treatment offer appropriate therapies: Rheumatic complaints are treated with the poison of the cobra, rattlesnake and sand viper. Snake poisons are also said to help with chronic pain, migraines, neuralgia, chronic kidney infections, asthma, neurodermatitis as well as hay fever and other allergies.

Cologne Zoo is far from such applications. His goal is simpler: the visitors should enjoy the snake - and under no circumstances should they be bitten.

Ziegler: "The scene of the accident must be secured, appropriate measures must be taken, the person must be calmed down and put in a stable lateral position or in a shock position, then the antiserum that we have stored in several places must be obtained while the emergency vehicle is closed Help is coming. "