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



## Dark241993 (Aug 24, 2009)

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


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## jsloan (Aug 24, 2009)

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 ...


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## Widowman10 (Aug 24, 2009)

jsloan said:


> 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 ...


i believe that is the LD50 iirc...



Dark241993 said:


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


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.


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## Moltar (Aug 24, 2009)

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.


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## Venom (Aug 24, 2009)

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.


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## Widowman10 (Aug 24, 2009)

Venom said:


> Figure on 5% for our three native "black" widows: L. mactans, L. variolus, and L. hesperus--the southern, northern, and western widow spiders, respectively.


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.



Venom said:


> Allergic reactions are also a real possibility, and there are documented deaths from this.


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). 



Venom said:


> 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.


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.


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## Venom (Aug 24, 2009)

Widowman10 said:


> 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.


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. 





> 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).


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 ):

http://www.telegraph.co.uk/expat/41...ert-after-two-die-from-black-widow-bites.html

http://www.bmj.com/cgi/content/full/333/7562/278-a

( 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, 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.


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.


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## Widowman10 (Aug 24, 2009)

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.


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## Venom (Aug 24, 2009)

FYI...120 KDa = 120,000 atomic mass units = 491 Plutonium atoms.


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## toolrick (Aug 25, 2009)

You missed in that comparison Phoneutria Sp., which venom it's more potent than widow and Atrax.

Ricardo


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## Venom (Aug 25, 2009)

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.


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## SNiDE (Aug 25, 2009)

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?


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## Widowman10 (Aug 25, 2009)

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.


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## jsloan (Aug 25, 2009)

Widowman10 said:


> 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.


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


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## Widowman10 (Aug 25, 2009)

jsloan said:


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


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...


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## Widowman10 (Aug 25, 2009)

> Like all Latrodectus species, L. geometricus has a medically significant neurotoxic venom. Dr. G.B. Edwards, a University of Florida arachnologist *claims that brown widow venom is twice as potent as the black widow venom*, but is usually confined to the bite area and surrounding tissue, as opposed to the Black Widow.


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



> Results: The mouse LD50 values for L. hesperus and L. mactans venoms were *0.64 mg/kg and 0.26 mg/kg, respectively.*


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



> Actual or alleged envenomations are attributed to the various local widow species, *which differ significantly in toxicity*, aggressiveness, and ecology (Finlayson, 1956; Maretic, 1971; 1978; 1983; 1987; McCrone, 1964; McCrone and Netzloff, 1965; Müller et al., 1989; Müller et al., 1992; Shulov, 1940; Shulov and Weissman, 1959).


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



> the *LD50 values of L. tredecimguttatus (ESV) were (0.16±0.03) mg/kg*


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


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## toolrick (Aug 25, 2009)

@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".

Ricardo


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## jsloan (Aug 25, 2009)

Widowman10 said:


> from: http://www.cirrusimage.com/spider_brown_widow.htm
> 
> from: http://www.informahealthcare.com/doi/abs/10.1081/CLT-100103826
> 
> ...


Thanks for the links.  Some good stuff there (except for the first one, though, which doesn't list any sources).


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## SNiDE (Aug 25, 2009)

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

Reactions: Like 1


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## Widowman10 (Aug 25, 2009)

jsloan said:


> Thanks for the links.  Some good stuff there (except for the first one, though, which doesn't list any sources).


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.


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## Venom (Aug 25, 2009)

toolrick said:


> @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.
> 
> ...


Thanks Toolrick!

But, that isn't in mg/ kg...hence, it would require math to convert to standard units, which I just hadn't done.


Widowman...were those subcutaneous LD50's? I'll have to look at those links when I have more time ( bed time now.) Thank you for those though.

-Venom.


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## Tim Benzedrine (Aug 25, 2009)

LD-50, Kilograms, Blah, blah, blah! All you need to know about the black widow is right here.

[YOUTUBE]EfTX6dw3pRI[/YOUTUBE]

Very probably not the first time this was posted and probably not the last.



_Slithers back to the Watering Hole_


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## Widowman10 (Aug 26, 2009)

Venom said:


> Widowman...were those subcutaneous LD50's? I'll have to look at those links when I have more time ( bed time now.) Thank you for those though.
> 
> -Venom.


no, they were the ESV values. subcutneous values were a little higher (as expected).


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## Widowman10 (Nov 2, 2010)

*bump for info*

thought i'd bump this up with some info i stumbled across the other day while reading some research papers. this is old, and not thorough by any means, but still can be useful. at least this is some hard evidence and not just speculation. JSloan, not sure if you've come across this, but you might find it interesting, who knows. anyway:



> The bites of Latrodectus geometricus are less toxic than those of L. mactans. Finlayson determined the minimum lethal dose of geometricus for mice (weighing 18G), guinea-pigs (weighing 350G), and rabbits (weighing 1,600G).
> 
> *Mouse-------------* geo: 0.6mg ________ mac: .05mg
> *Guinea-pig---------* geo: 2.0mg ________ mac: .50mg
> *Rabbit-------------* geo: 12.0mg ________ mac: 3.0mg


so i guess these are like "LD100" values  but whatever

(taken from Latrodectism in South Africa by F. Zumpt)


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## jsloan (Nov 5, 2010)

No, I hadn't seen that.  Thanks!


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## Venom (Nov 5, 2010)

Again, thank you Widowman. Good stuff! :clap:


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