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How potent is a Black Widow's venom????

Discussion in 'True Spiders & Other Arachnids' started by Dark241993, Aug 24, 2009.

  1. Dark241993

    Dark241993 Arachnosquire

    just wondering????? if there are any bite reports or first had accounts or w/e please share =D
  2. jsloan

    jsloan Arachnoangel Old Timer

    Drop for drop, on a dry weight basis, it's said to be about 15 times as potent as a rattlesnake's. Whatever that means ...
  3. Widowman10

    Widowman10 Arachno WIDOW Old Timer

    i believe that is the LD50 iirc...

    there's a few bite reports here, just gotta search a little. most people i've talked to with bites from these gals have not had very bad side effects at all. still wouldn't advise playing with them as i've read they can potentially be quite nasty.
  4. Moltar

    Moltar ArachnoGod

    My understanding is that a bite will cause a lot of pain and discomfort ranging from a couple of days to a week. Not really life threatening unless you're unhealthy already, elderly or a small child. Still it's nothing to mess around with. There is no necrotic effect (blistering, skin rotting nastiness like a recluse bite) just nasty neurotoxic effects like labored reathing, muscle pain, etc.

    You're not that likely to be bitten unless you're really hassling them. Their defensive behavior if disturbed in their web is usually to web the bejeezus out of the intruder. A bite is generally their last resort. Don't take it for granted though, an envenomation would definitely ruin your day.
  5. Venom

    Venom Arachnoprince Old Timer

    Latrodectus mactans ( southern black widow ) has an LD50 ( lethal dosage in 50% of test mice ) of 0.90 mg/ kg ( milligrams of toxin necessary to kill a 1 kilogram animal ).

    The lower the LD50 number, the HIGHER the toxicity--because it is requiring less toxin to be lethal. Here is a comparison of toxicities:

    Eastern diamondback rattlesnake: 14.6 mg/kg
    Gaboon viper 12.5 mg/kg
    Banded krait: 3.6 mg/kg
    King cobra 1.7 mg/kg
    Black widow 0.90 mg/kg
    Black mamba 0.32 mg/kg
    Sydney funnelweb 0.16mg/kg

    So, it's really pretty potent. Averaged across all demographics, the fatality rate for Latrodectus envenomation by the species of major importantce, is 4-6%, varying by species. Figure on 5% for our three native "black" widows: L. mactans, L. variolus, and L. hesperus--the southern, northern, and western widow spiders, respectively.

    As for effects, a Latro bite that actually carries venom--not a "dry" bite", will produce intense suffering for 24 - 48 hours, unless treated. Fatality is most likely in those of compromised or age-weakened cardiovascular, respiratory, neurological or muscular systems. There is also a risk for renal failure, and anaphylactic shock--both of which may be fatal.

    With antivenom, survival is 99% guaranteed. We have not had a fatality in this country since antivenom was introduced back in the 1980's. However, in places where antivenom is not readily available, deaths continue. Allergic reactions are also a real possibility, and there are documented deaths from this.

    Bottom line: don't mess with them. You'll probably be ok....but, they're mucho toxic and NOT fun. Oh..and a side note: a medical doctor will NOT give you antivenom unless your case is life-threatening. You'll get "supportive therapy," which means they will try to alleviate your suffering, but it's not going to be fun.
  6. Widowman10

    Widowman10 Arachno WIDOW Old Timer

    nice post on the LD50 values. always good information and comparison of values. i don't know about a 5% fatality rate though. of the many people i've known to be bit, i've never heard of one dying and statistically it should be 1 in 20. i know about elderly folks and whatnot, but you would think you would hear more often in news and media about deaths from a widow. i don't think it's quite that high.

    not saying you are wrong by any stretch, but do you have a link so i can check these out? i am very interested in this as i have studied some reactions to venom injection in college. also the possibility of allergic reactions to venom on a first-time envenomation. all bets are off on second-time envenomations as anything can happen, but i'm not so sure about an innate response to a first-time envenomation (which is invariably what most widow bites will be).

    yes, as you can only receive latro anti-venin once in your lifetime. which, unless truly life-threatening, would be pretty pointless. you will just have to ride out the pain.
  7. Venom

    Venom Arachnoprince Old Timer

    It isn't that high in the mainstream of the population--that, and the fantastic effectiveness of the anti-venin, is the reason you don't hear of many deaths ( in THIS country ) from latrodectism. The reason the official fatality rate stands at 5% is that this is the number you get, when you AVERAGE the fatality rateS ( plural!! ) of all demographics: averaging across children, tweens, young-mature, mature, elderly; as well as the 100% healthy, and the ( really much larger than you'd think ) portion of the population who bear some heightened vulnerability to the toxin. You might be surprised to know that if you even have hypertension--that is a heightened risk factor for death from latrodectism. Now...tell me you don't know someone with high blood pressure--honestly, I'm sure you probably can't. At least, it is a very prevalent condition, which seriously affects the body in conjunction with latrotoxin envenomation, directly affecting the kidneys in conjunction with the risk for rhabdomyalsis ( clogging of the kidneys via protein-spilling by ruptured muscle cells --caused by the violence of latrodectism's cramping ).

    Another common risk factor would be obesity, as the heart is already at an elevated work-load, trying to pump blood through a mass of adipose capillaries. Well, the cramping heightens blood pressure, AND puts an undue strain on the heart as it tries to compensate for the greatly increased rate of oxygen consumption ( just as if you were running a marathon: you cardiorespiratory system is being taxed ).

    High blood pressure, obesity. The risk factors for elevated fatality rate from latrodectism are MUCH more prevalent than you would think, if you believe that anyone of roughly ages 15 - 50 is "safe" and in the clear.

    But, in any case, you must understand that the 5% is an average. Certainly there are some groups who could be at probably 15% fatality, IF we had no antivenom. But we do, so even these persons are able to be saved by medical intervention. We don't see the effects of the 5% averaged rate in THIS country. Believe me, take away supportive therapy and antivenom intervention...and we'd be having deaths every year, like we used to only a few decades ago.

    Certainly. Here is a link to a pretty well-documented death from latrotoxin-induced anaphylaxis, that happened about 6 years ago in Croatia ( L. tredecimguttatus ):



    ( the first link has some info wrong...like the exact species involved. The second article is scholarly, but I can't access it without a membership. ) IN any case, it makes perfect sense that anaphylaxis should be possible from this syndrome, because it involves a 120 KDa protein, which is just enormous ( and therefore highly "visible" to the immune system. Being small and "invisible" is what keeps peptide-based tarantula venom from being an allergic risk. Widow venom is the COMPLETE opposite ).

    Yes, being protein-based again, the anti-venom is just as likely to CAUSE a serum reaction as it is to cure the first problem: the venom. So, a single use of the anti-toxin is all one can have without the risk of anaphylaxis outweighing the benefits of using it.
  8. Widowman10

    Widowman10 Arachno WIDOW Old Timer

    the averaged rates make sense if all other countries are taken into account. that still seems very high! any idea what the numbers for the US are? <1% i assume?

    i'll have to do some more research on the structure of latrotoxins. i know that T venom is very small (small peptides) and thus can escape from being 'seen' by the immune system-- which will not cause an allergic reaction. if it really is a massive structure, it could create problems unlike other venoms.
  9. Venom

    Venom Arachnoprince Old Timer

    FYI...120 KDa = 120,000 atomic mass units = 491 Plutonium atoms.
  10. You missed in that comparison Phoneutria Sp., which venom it's more potent than widow and Atrax.

  11. Venom

    Venom Arachnoprince Old Timer

    I don't have a convenient LD50 source for Phoneutria spp. . I admit I do need to find one. The data I saw was in really goofy units, and I didn't feel like doing the math.
  12. SNiDE

    SNiDE Arachnopeon

    Is there any reliable info regarding differences in venom between latrodectus species, or even subspecies, like m. mexicanus? Or is it all basically the same?
  13. Widowman10

    Widowman10 Arachno WIDOW Old Timer

    there might be data (i haven't seen it) between the different species, but there certainly is a difference. some have much more potent venom.
  14. jsloan

    jsloan Arachnoangel Old Timer

    If you haven't seen any data, why do you believe there's a difference?
  15. Widowman10

    Widowman10 Arachno WIDOW Old Timer

    haven't seen. heard. ;) but then again, this is just hearsay. plus, spiders from the same genus often have very different venoms. loxosceles, atrax, others. they vary even among genus. i could search around a little bit and find out.

    this is what i remember:

    geometricus has worse venom than native blacks- but they don't inject as much.

    tredecimguttatus has pretty bad venom

    bishopi i've never heard of anyone having any problems from

    i'll search around and see if i can find anything. probably not, but who knows... :D
  16. Widowman10

    Widowman10 Arachno WIDOW Old Timer

    from: http://www.cirrusimage.com/spider_brown_widow.htm

    from: http://www.informahealthcare.com/doi/abs/10.1081/CLT-100103826

    from: http://www.tolweb.org/Latrodectus/93274 (sources cited)

    (pretty high!)
    from: http://www.zoores.ac.cn/qikan/epaper/zhaiyao.asp?bsid=4779
  17. @Venom:

    An article taken from wikipedia, I do not know if it's 100% true or not; someone else might post on this as well.

    "P. nigriventer venom contains a potent neurotoxin, known as PhTx3, which acts as a broad-spectrum calcium channel blocker that inhibits glutamate release, calcium uptake and also glutamate uptake in neural synapses. At deadly concentrations, this neurotoxin causes loss of muscle control and breathing problems, resulting in paralysis and eventual asphyxiation. In addition, the venom causes intense pain and inflammation following an attack due to an excitatory effect the venom has on the serotonin 5-HT4 receptors of sensory nerves. This sensory nerve stimulation causes a release of neuropeptides such as substance P which triggers inflammation and pain. [4]

    Aside from causing intense pain, the venom of the spider can also cause priapism in humans. Erections resulting from the bite are uncomfortable, can last for many hours and can lead to impotence. A component of the venom (Tx2-6) is being studied for use in erectile dysfunction treatments.[5]

    The amount of Phoneutria nigriventer venom necessary to kill a 20 g mouse has been shown to be only 0.006 mg intravenously and 0.0134 mg subcutaneously as compared to 0.110 mg and 0.2 mg respectively for Latrodectus mactans (Black Widow).[6] This ranks Phoneutria venom among the most deadly found in spiders".

  18. jsloan

    jsloan Arachnoangel Old Timer

  19. SNiDE

    SNiDE Arachnopeon

    Surprising stuff thanks for the research! Worth noting there's alot of misconception about L. Tredecimguttatus bites in europe, most travel literature stating that it is only just medically significant and not as dangerous as other foreign latrodectus species
    • Like Like x 1
  20. Widowman10

    Widowman10 Arachno WIDOW Old Timer

    yeah, there were some good scientific sources in some, not in others ;)

    this was just a perfunctory search. i would like to see (if anyone has actually ever done it) an LD50 chart for many of the other common latros. i would put money down that no one has tested all 31-ish species of latros.