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Tarantula venom, and anaphylaxis

Discussion in 'Tarantula Questions & Discussions' started by Matabuey, Sep 16, 2016.

  1. Matabuey

    Matabuey Arachnosquire

    There is a lot of misinformation on these boards and other boards dedicated to tarantulas, with regards to their venom. I don’t particularly blame anyone, as often they’re just regurgitating what they’ve read elsewhere.

    As many of you have seen, I have had a lot to say on the subject. I’m no toxicologist, but I have spent a lot of time trying to digest information that is presented in papers relating to venomous animals on the whole – ever since I started keeping venomous snakes.

    There may be some people who haven’t read my previous comments, so I will be including them in this thread (sorry to those of you, whom have read parts of this before), as well as new information/facts relating to tarantula venom and anaphylaxis.

    Stromatopela calceatum: The most “toxic” Tarantula

    Often touted as the most dangerous/toxic Tarantula around, but is it?

    We simply do not know, from reading the many bite reports around on this forum and several others, to me it seems as if systemic effects from Stromatopelma are of no greater medical significance than those symptoms produced by Lampropelma, Poecilotheria, or Haplopelma, etc.

    I actually cannot find anything to support the notion that this tarantula is the most dangerous. The disposition of the animal has most likely contributed to this inflated perception. I would say it's actually completely incorrect to suggest it's the most dangerous, or "most potent tarantula" without adequate research.

    Often phrases such as “potent venom”, “highly toxic”, “incredibly dangerous”, “life threatening”, are wrongly used to describe this species. These phrases should be synonymous with animals that pose a serious and immediate risk to one’s life, not an animal with a mildly ‘toxic’ venom.

    Many of you have read Phillip Charpentier’s entry into Exothermae, regarding S.calceatum, if you have not, you can read it here: http://www.reptileforums.co.uk/forums/6087262-post9.html

    Part of his post, has potentially contributed to this notion that this is the most dangerous Tarantula around. This part in particular “I am sure that, without the immediate intervention of a primed and ready venom extraction kit, this young fellow might well have died” – categorically incorrect.

    Further to that his comment “Stromatopelma is the link between the relatively harmless mass of Theraphosids, and the few species that can be life-threatening to man.” – A view that is supported by… no one else or any data.

    The document linked below, categorically states just how ineffectual extraction kits are, and how they can actually worsen effects of the bite – from a world renowned expert on clinical envenomations. (His view is supported by pretty much any medic or toxicologist worth their mettle).


    The only means we have of determining how dangerous a venomous animal is, is by the rough approximation, LD.50 and known deaths.

    From: Venom of an aggressive African Theraphosidae (Scodra griseipes): milking the venom, a study of its toxicity and its characterization

    The LD.50 is around 8.1 mg/kg for a young female, and 9.5 mg/kg for an adult male.

    The max average yield from a young female is 18.7 mg - thus it is able to kill a 2.3kg human.

    The max yield obtained from a young female, was 46.6 mg - able to kill a 5.75kg human.

    The max average yield from an adult male 13.4 mg - able to kill a 1.4kg human.

    The max yield obtained from an adult male 49.6 mg - able to kill a 5.22 kg human.


    While this method is not the most accurate in every single scenario, however when looking at the majority of venomous animals and their LD.50’s – usually the ones with the lower number, have proven to be the most dangerous to humans (providing they have a large enough yield – obviously).

    You can compare Oxyuranus microlepidotus (inland taipan – 0.025 mg/kg sc) to Crotalus lepidus klauberi (banded rock rattlesnake, 23.95 mg/kg sc), or P. nigriventer (brazilian wandering spider = 0.13 mg/kg iv) to S.calceatum (Feather leg baboon – 8.1 mg/kg iv), and those with the lower LD.50 are considerably more dangerous.

    However, I said usually for a reason. There are a few exceptions to this, such as Atrax robustus (Sydney funnel web), has a relatively low standard LD.50 value, but its clinical effect on humans is much greater than expected. Also when comparing Tropidechis carinatus (rough scaled snake) which has a low LD.50 in mice, compared to a snake with higher LD.50 in mice, Notechis scutatus (tiger snake). You would assume N.scutatus to be more medically significant, yet they’re almost as dangerous as one another when considering clinical effects in humans.

    Having said that, it can be shown from the countless envenomations from tarantulas, that humans do not react in an unexpected fashion. So it would be plausible to use LD.50 values as a reasonable approximation, for toxicity towards humans.

    iv: Intravenous sc: subcutaneous

    There are many wrong figures on these boards, such as people stating that some species have an LD.50 of 0.7mg/kg.

    But they must’ve skimmed over the part where they said they isolated a particular toxin. Which is completely different to an actual envenomation, as you’re not just injected with a particular toxin, you’re injected with the full cocktail, as well as the proteins, you have things such as inorganic ions and salts, free acids, glucose, nucleic acids, free amino acids, etc.

    For example, that 0.7mg/kg of a particular toxin, may ‘reside’ in 30 mg of the other constituents, so the actual LD.50 will be much higher.


    It goes without saying, the larger the yield, the more dangerous said animal will be to you – it’s one of the other factors to consider. If a Taipan could inject 2000mg, it would be more dangerous than one that could only inject 0.000001 mg.

    Tarantulas simply do not have the capability to produce enough venom to be life threatening in the majority of situations.

    A 6 month old child? Yes.

    A three year old? Highly unlikely, even 3 year olds are able to survive Latrodectus bites without needing antivenom. http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3200105/

    Venomous animals will rarely give their full yield in a defensive bite, which is another factor to consider. Venom is a highly precious substance that requires lot of resources for a venomous animal to produce. T’s can also dry bite, even Satan himself - S.calceatum.

    As an interesting side point. Yields can be affected by state of nutrition (not in the way you’d necessarily think at first), and moulting. Taking into consideration the opisthosoma/prosoma ratio, and time from moulting, some interesting things were found – with Coremiocnemis tropix.

    For example: “The present results demonstrate that a change in the long-term state of nutrition (as expressed in the o/p ratio) does not significantly affect the venom yield. However, towards very high and low o/p ratios, there seems to be an increase of spiders that do not yield any venom. This might be explained in two ways; badly-nourished spiders (with a very low o/p ratio) do not have sufficient energy resources for venom synthesis, whereas extremely well-nourished spiders (with a very high o/p ratio) have a decreased demand for venom, as they do not need to capture prey for some time.”

    Taken from this paper: http://www.ncbi.nlm.nih.gov/pmc/articles/PMC3086189/

    Yields from T’s are far too low to cause any real concern, many species haven’t been studied to obtain yields, but it’s fair to say this covers enough to give a rough idea. We aren’t going to have any tarantulas producing 100mg of venom.

    B.epicureanum 14.7 ± 2.6 mg

    P.regalis 8.7 ± 1.1 mg

    C.darlingi 4.0 ± 0.1 mg

    S.cal (f) 9.7 ± 9 mg

    (m) 6.7  ± 6.7 mg

    Pterinochilus sp 4mg


    To date there have been no deaths recorded for any tarantula species. Others will claim “They have killed, we just don’t know it yet” – which simply doesn’t hold any water. There are enough cases of envenomation, in captivity and in their natural habitat – yet, not a single person has a death to report.

    I could say the same for Boiga dendrophila, and label it a life-threatening species – incorrectly. In 99.9% of cases it will not kill, thus isn’t ‘worthy’ of the title “life-threatening”. What would we then call highly dangerous spiders or venomous snakes…’Extra life threatening’?

    It is all too easy to suggest they’ve killed without any supporting evidence.

    Even when Phillip went to Sierra Leone, no one had a death to speak of – it’s not something people forget. It is also a story people would pass down generation to generation, so the children know to be wary of these animals. 9 people were bitten in his short trip...for these plantation workers, being bitten would seem to be a relatively common occurrence.

    In Cambodia, for example, children hunt tarantulas to eat – young children would almost certainly have been bitten by OW’s, but still there are no deaths to report.


    I recently spoke to Wolfgang Nentwing over a few brief emails, if you’re unaware who he is, he has been at the forefront with regards to spider venom for several decades now. He gave me his permission to share the details.

    He put it quite succinctly: “There is no lethal risk from tarantula spiders. A few genera among them (Poecilotheria) are more dangerous than others”.

    “Comparing Latrodectus with tarantulas? Latrodectus has a very potent venom, acting strongly on the membranes of nerve cells. Tarantulas have the “usual” simple spider venom cocktail, moreover, their venom is not so potent. Theraphosid bites are generally rather harmless.”

    “Latrotoxins (from widow spiders) are very large, the largest toxins among spiders (140 kDa = 1400 amino acids) and they construct pores into membranes. They are only known from Latrodectus and a few other theridiid spiders. All other neurotoxins in spiders are in the range of 5 to 15 kDa (50 – 150 amino acids), thus much smaller. They inhibit ion channels, usually a reversible action. These small toxins are known from mygalomorph spiders (tarantulas) and all other spiders.”

    This last quote, is more so to do with my points on anaphylaxis which will come later.

    Obviously, in very acute circumstances a tarantula may well kill someone, but they should not be labelled, potentially deadly, incredibly potent, highly dangerous, or any of these ridiculous phrases that are so often used.


    Tons of interest in this topic and speculation, some correct to a degree and others not so correct.

    So far there isn’t an actual case to study with regards to anaphylaxis and tarantula venom. Unlike venomous snakes or Latrodectus which have produced anaphylaxis – but there may well be a good reason for that.

    In general tarantula venoms consist of much smaller proteins, as outlined by Wolfgang, the neurotoxins are around 5 to 15 kDa (50 – 150 amino acids), compared with that found in Latrodectus which are as large as 140kDa (1400 amino acids), some proteins in venomous snakes can be as large as 350kda (3500 amino acids).

    A large percentage of T venoms contain proteins below 10 kDa (100 amino acids). Supported by various studies on T venom, there are some larger components, but they’re much less common (a couple of papers, but can link more):



    Anaphylaxis is already a rare event, whether it’s from venomous snakes or true spiders. But there are no cases in people who are bitten by tarantulas – more than once. Important to add here that, you cannot suffer anaphylaxis on your first exposure.

    When you hear of people suffering anaphylaxis from a Bee sting on their “first exposure”, they often were too young to remember the first time they were stung, or they have been stung by other vespids – which share some of the same common allergens.

    Why might that be, that we haven’t seen a case of anaphylaxis from Tarantulas, when there are so many keepers of these animals around the world?

    For a protein to elicit anaphylaxis it must meet several conditions. One of those conditions, is size of the protein.

    “An allergen must therefore contain at least two IgE binding sites (epitopes), each of which will be a minimum of approximately 15 amino acid residues long, in order that antibody binding can occur. This implies a lower size limit for protein allergens of approximately 30 amino acid residues (M.W. of approximately 3 kD).”

    Naturally it follows, the larger the amino acid, the more IgE binding sites are present, thus being much more immunogenic. Tarantulas also contain nucleic acid, which is a poor immunogen by itself.

    Taken from: http://toxsci.oxfordjournals.org/content/55/2/235.full

    Potent immunogens, are those over 100kDa, and those below 10kDa are said to be weak immunogens (T venom is mostly below 10kDa). (http://megaslides.com/doc/1395182/immunology) – page 52 states this, and you can bring up various papers on the internet that also state the same.

    Is it possible to suffer anaphylactic shock to tarantula venom?

    From the information we have, and our understanding of how anaphylaxis works – yes, it is possible.

    BUT considering that anaphylaxis is rare in venomous snakes or Latrodectus sp, which contain much more potent immunogenic constituents, and that tarantula venom is primarily made up of weak immunogenic constituents, it would be wise to assume that it is unlikely one would suffer anaphylaxis. A view that has been shared by other toxicologists/immunologists previously.

    End note:

    These animals deserve respect, because they can cause some systemic effects. But are they deadly? No. Are they highly venomous? No. Are they likely to kill a young child or an adult? No. Could they kill a 6 month old baby or a frail elderly person? Quite possibly. Could they kill a loved pet? Quite possibly.

    So just like you wouldn't let a Burmese python escape around your pets, or young family, it's wise to be prudent with any animal that is armed with venom.
    Last edited: Sep 16, 2016
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  2. Chris LXXIX

    Chris LXXIX ArachnoGod Active Member

    Avoid bites in the neck, you pundit. Avoid u_u

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  3. KezyGLA

    KezyGLA Arachnoking

    Great info. Some which I have read before. It does my head in when people say that certain species are 'very dangerous'. Most animals can be dangerous. It sometimes feels like fearmongering.
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  4. Estein

    Estein Arachnoknight

    Thank you so much for this collection of information. I will certainly be referencing this in the future!
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  5. Toxoderidae

    Toxoderidae Arachnoprince

    wonderful post.
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  6. Moonohol

    Moonohol Two Legged Freak

    Loved reading your previous posts, and I think it was a splendid idea to collect all of this info in to one place! Definitely deserving of a sticky.

    Oh and in regards to @14pokies comment... looks like it's too late now :rolleyes:
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  7. tnerd93

    tnerd93 Arachnopeon

    post like this, after a post with some of the info contained in this thread

    im not just making it up lol
  8. Poecimon

    Poecimon Arachnopeon

    Long time lurker here, frequent other forums, signing up to quite literally say thanks for this information and backing it up with solid sources.

    You're the only person ive seen across any forum that's actually put in some real effort to understand the situation, speak to professionals, and understand the science that is out there. Too many people are too lazy (me included) to spend their time looking into this, or they prefer to make their own opinion up based off folklore. Well done :)
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  9. KezyGLA

    KezyGLA Arachnoking

    Posts proving that things are unproven are beneficial to certain keepers. It beats the 'S cal. Or H mac bites you in the nuts you will have an aneurysm and croak'

    People who live in these areas are quite regulary bitten. Yet not a recorded death. Remember to not acquire Stromatopelma. It is satan in spider form and will eat you whole.
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  10. Amazing post, great information all around, I'll agree on the sticky.

    One thing I didn't notice you mention is bite placement, that's what I think of when I think of a fatal bite, not necessarily the power of the venom. I would be interested to see what that affects of being bitten on the neck near an airway, or in the chest, somewhere that swelling could cause a life threatening situation on a full grown adult. Not enough to try it myself though!

    However in that scenario it wouldn't technically be the venom that caused the death, but a mechanical issue in the respiratory system, which was caused by the venom, circle time!

    Anyway that's just my thought, sure the venom itself may not kill, but there is always the chance of that lucky bite
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  11. Jeff23

    Jeff23 Arachnolord Arachnosupporter

    Nice information.

    But any animal that puts you into the hospital is dangerous. While your odds of dying from spider venom may be lower, your odds of dying of a different illness acquired at the hospital are much higher.

    I like to avoid hospitals.
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  12. Matabuey

    Matabuey Arachnosquire

    There have been bites to the shoulder, or neck - both from S.cal, majority of effects were gone within 6 hours.

    If you're talking about mechanical damage to the trachea for example, sure that could be a dangerous situation. But it's an acute set of circumstances.

    Like @KezyGLA said, any animal can be seriously dangerous given the right set of circumstances, horses, dogs etc.

    I never said they weren't dangerous to a degree.

    But the majority of bites do not end up in hospital, few envenomations from tarantulas require a visit to the hospital. Just go look at the bite reports section, it will be a very small number that felt the need to go to hospital.

    They do not pose an immediate risk to ones life, nor do they cause unmanageable systemic effects. Different animals pose varying degrees of danger, and tarantulas are low down on that list.
    Last edited: Sep 18, 2016
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  13. Jeff23

    Jeff23 Arachnolord Arachnosupporter

    Sorry. I probably could have worded it better. I was not disagreeing with your comments. You are talking about direct consequences of a T bite. My comment was related to indirect consequences. This could be from a dog bite or even a non-animal injury. Hospitals in general are a risk that is higher than the reason you are there.
    Last edited: Sep 18, 2016
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  14. ratluvr76

    ratluvr76 Arachnodemon

    MOD NOTE: The information in this post is phenomenal. Good job on putting it together, great presentation. Thank you @Matabuey .
    I've stickied this thread and left it open for further discussion, please everyone be civil. :)

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  15. The Snark

    The Snark هرج و مرج مهندس Old Timer

    Just to mention something regarding anaphylaxis. A substance need not contain a toxin to cause it. In fact, it need not contain a harmful substance at all. Anaphylaxis is the body's immune system freaking out due to a foreign substance or it responding to a second dose which it improperly handles.

    The other thing about anaphylaxis is most people don't know or recognize many of the symptoms. Airway restriction is the most obvious but there are numerous others: (Grabbing a convenient list from a paramed site)
    • Abdominal pain
    • Feeling anxious
    • Chest discomfort or tightness
    • Diarrhea
    • Difficulty breathing, coughing, wheezing, or high-pitched breathing sounds
    • Difficulty swallowing
    • Dizziness or lightheadedness
    • Hives, itchiness, redness of the skin
    • Nasal congestion
    • Nausea or vomiting
    • Palpitations
    • Slurred speech
    • Swelling of the face, eyes, or tongue
    • Unconsciousness
    These are common symptoms but there are numerous others. Leg cramps for example. This can be extremely difficult to diagnose and even hemotoxicologists can miss them.
    Last edited: Sep 18, 2016
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  16. symbol

    symbol Arachnopeon Active Member

    So, something I've been wondering re: tarantula bites... What exactly can be done at a hospital to treat a bite? Apparently venom extraction kits aren't really helpful. Anaphylaxis is highly unlikely, so getting epinephrine or antihistamines or whatever isn't likely to be relevant. AFAIK they don't make tarantula antivenins. And even if they do, I doubt antivenins for non-native species would be commonly kept on hand in most hospitals. So, what exactly are you going to the hospital for?

    I guess if there was a lot of mechanical damage, dressing the wound and/or getting stitches might be necessary. But other than that, what are they likely to do for a tarantula bite at a hospital?
  17. sdsnybny

    sdsnybny Arachnogeek Arachnosupporter

    Treatment for the possible extreme cramping, pain management, heart issues, and swelling that occurs. Some of the bite reports paint an ugly picture of what goes on in a full on wet bite form some of the OW T"s
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  18. The Snark

    The Snark هرج و مرج مهندس Old Timer

    Unless a specific antidote of some form is available the rule of thumb is to treat symptomatically. That's a very broad answer as symptomatic treatment can range from a band aid to blood transfusions or even organ donor.
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  19. The Snark

    The Snark هرج و مرج مهندس Old Timer

    To clarify. A toxin enters the body. There are numerous actions that a hospital can take beyond immediate life saving trauma intervention. Monitoring blood chemistry and preventing or minimizing damage to the kidneys and liver is often first called on. There are hundreds of drugs that can be used to stabilize the patient and minimize the toxic effects; the kidneys can be flushed, aiding in removal of the toxin and preventive measures taken to protect the liver. The general plan is minimizing the toxic effects through symptomatic treatment and giving the body the best possible chance to reject and discharge to toxins. This is usually done even if a specific antidote is administered.
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  20. viper69

    viper69 ArachnoGod Old Timer

    @tnerd93 Don't be so pessimistic, here's the Sticky. ;)
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