| about BITES & VENOM |
| Invertebrate Venom |
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| Retired Professor of Anatomy, Ian Gibbins, has kindly shared his thoughts with us to help people learn: The proteins (or their peptide sub-components) in the toxins are nearly always the things that generate an allergic reaction, and those proteins are unique for each species. So if you are allergic to honey bee stings, you are not necessarily going to be allergic to a wasp or ant sting. The reactions people get to stings are due to a variety of effects of the components of the venoms. Part of the response is a generalised inflammatory response to a foreign protein = localised redness, swelling and possibly itchiness (as in a mosquito bite). This reaction is partly mediated by sensory nerves (the ones I spent half my life working on!), partly via histamine released from inflammatory cells in the skin (mast cells). If you are lucky, it ends there (or at least after an hour or so). If you are not, you may end up with a more complex on-going immune / inflammatory response which may result in local bleeding in the skin => the red wheals and blotches, or even small blisters, that surround bites / stings sometimes. This reaction may last a week or more, and runs the risk of becoming infected if the skin breaks (either by blistering or scratching). The excessive pain caused by many hermopteran stings (bees, wasps, ants) is due to specific peptide components of the venom that directly target ion channels or receptors on the endings of sensory nerves in the skin. This response is not directly related to the inflammatory response. If you get significant swelling around an insect bite or sting, that means that the inflammation has extended well beyond the bite zone and into the lymphatic system, usually as a result of your immune system over-responding (ie, a more or less allergic reaction). Opinion is divided over the best way to deal with that. Movement and exercise increases overall blood flow and will help drain lymphatic fluid away. But a compression bandage, if applied early, can help prevent the swelling from occurring in the first place. The other complicating factor is that you immune system can respond in two opposite ways to repeated stings / bites from the same species. The good adaptive way is that you become desensitised to the venom: the immune system just deals with it to effectively minimise or neutralise the effects. This is what happens to many people who move to the tropics: their initial (bad) responses to things like sandflies improves with time. The bad (maladaptive) way is that your immune system develops a super-sensitivity to the proteins in the venom => allergic, and possible anaphylactic reaction. Ian Gibbins | |||||||||
| Spider Wasp Venom |
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| Retired Professor of Anatomy, Ian Gibbins, has kindly shared his thoughts with us to help people learn: I've just looked up what is known about the venoms used by the wasps to paralyse the spiders. It turns out there's not a lot known, mainly because there hasn't been much work done... As is the case for many venoms, there actually is a cocktail of active ingredients. The one most likely to cause the paralysis is specfic for an ion channel in the nerves. It blocks this channel and thereby prevents the nerves from firing their electrical impulses that are required to activate the muscles etc. This action is not very different from that of puffer fish and blue-ring octopus toxins. In us, it causes local anaesthesia and paralysis, if you get enough of it... Wasp stings, especially from spider wasps, are notorious for being extremely painful. This is due to another suite of compounds in the venom whcih probably indirectly activate and then sensitise pain sensitive nerve fibres. I doubt anyone knows what these compounds do in the spider prey. The venoms also contain anti-bacterial compounds, which is a pretty handy thing to have if you plan on keeping your spider for a while... Ian Gibbins | |||||||||
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