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Measuring Venom Toxicity

There are many ways of measuring venom toxicity, looking at either whole venom, or specific venom components or activities.

The LD50

The Lethal Dose 50% (LD50) is that dose of a substance that will kill, on average, 50% (half) of all the test animals.

The usual animal used is the mouse. The type of animal used can affect the toxicity (LD50 level); some types of animals are far more susceptible to a particular toxin than others. An example is funnel web spider venom. Most test animals are almost immune to this venom, yet humans and day old mice can die following injection of the venom (in the case of humans, this is accidental injection of venom, through a bite from a live spider). LD50 tests obviously cannot be performed using humans, so we must always guess if the LD50 dose for the test animal truely reflects likely toxicity in humans.

The route of injection of the toxin varies; it may be into a vein (IV), into a muscle (IM), into the abdomen (IP) or into the skin (SC). The route of injection can make a big difference to the toxicity (LD50 level), because for some toxins, injection into the blood is much more potent than injection into muscle or skin. Most bites are into the skin, so approximate SC injection.

Specific Toxicity Tests

There is an increasing range of tests available to determine particular types of toxicity. Some involve live animals, but most involve test tube type systems. Using this variety of test systems, it is possible to look for toxin activity affecting blood clotting, blood vessel injury, skin injury, blood cell destruction, kidney damage, heart muscle damage, voluntary muscle damage, neurotoxicity of many types and a variety of other toxin activities.

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