Understanding LD50 values in Latrodectus sp.

[JaySteel]

Hi everyone. Having read through the excellent website of @Widowman10, I have a couple of questions regarding the venom of Latrodectus sp.

The LD50 values are quoted by Widowman10 as being:

Latrodectus geometricus = .43 mg/kg (IV) & .223 mg/kg (IP)

Latrodectus hesperus = .84 mg/kg (IV)

Latrodectus mactans = 1.39 mg/kg (IV) & .90 mg/kg (SC)

Latrodectus bishopi = 2.2 mg/kg (could be IP)

Latrodectus variolus = 1.8 mg/kg (IP)

Based on the figures above does Latrodectus geometricus have the most potent venom of the Northern American Latrodectus species, but because the yield of venom is considerably lower than other Latrodectus species the bite of Latrodectus geometricus is not usually medically significant to humans?

Which of the Northern American Latrodectus species is considered to be the most dangerous to humans, taking into account both the potency and yield of the venom? I've read conflicting answers to this question from varying online sources so I imagine opinion varies on this topic.

Thanks for your help.

 

[The Snark]

LD 50 is the exact amount of toxin delivered to produce the result of the death of 50% of the test animals. The results are called averaged absolute values. The only variables involved are the mechanism of dosage delivery; IP - Intraperitoneal, SC - Sub Cutinaceous, or IV - Intravenous. It does not take into account the amount yielded by individual spiders or species, the mechanism of delivery - chelicerae or any other attributes of the spider, conditions such as environmental factors or the species of animal bitten other than the control.

So yield from spider to spider or species to species is not a factor in the above LD 50 testing. Or, normally, all LD 50 tests.
Variations of the procedures require the tests to be labeled as non standard and explanations written up in the white paper. Variation testing can not be compared to the lab standard LD 50 test except as comparison reference. As example, environmental factors outside of a given norm, pre-existing conditions, gestation, zero G etc.

Note: Some of the terms I use may be archaic. It's been a few decades since I (dis)graced the labs.

 

[JaySteel]

The Snark - Thanks for your knowledgeable reply. Unfortunately it doesn't directly answer either of my questions though.

 

[The Snark]

Based on the figures above does Latrodectus geometricus have the most potent venom of the Northern American Latrodectus species,

Yes.

but because the yield of venom is considerably lower than other Latrodectus species the bite of Latrodectus geometricus is not usually medically significant to humans?

Yield not defined or cited in the above. Variables need assigning. Yield meaning what? Venom produced or venom delivered? Venom delivered can not be accurately measured.

Which of the Northern American Latrodectus species is considered to be the most dangerous to humans, taking into account both the potency and yield of the venom? I've read conflicting answers to this question from varying online sources so I imagine opinion varies on this topic.

No data. Again, unassigned variables. As you mentioned, conflicting answers due to lack of data: A. Population densities of humans to spiders. B Accuracy of data relies heavily upon unqualified sources - usually from medical professionals* determining the mechanism of injury was from a certain species of spider without doubt. (Most often this relies on guesswork) C. What data the medical professional bases their conclusions on is often partly from unqualified members of the general public. D. Actual amounts of venom delivered to a patient can not be accurately measured. E. Tendency of properly identified spiders to come into contact with humans. Also F. A study, if possible, of how common are dry bites and do these bites vary from species to species?
Thus the ambiguity "... opinion varies on this topic."

*Medical professionals who are also qualified entomologists are quite rare.

BTW The elephant in the room is not mentioned: "the bite of Latrodectus geometricus is not usually medically significant to humans?". Going by what data is available, which mostly comes from poison control surveys, extremely few Latrodectus bites from all species are medically significant. Both bites I have had (L Hesperus and suspected Hasselti) were regarded as trivial. Clean wound and observe for symptoms. If obvious symptoms develop (they didn't) go to an ER. Bring the spider with you if at all possible.(My suspected Hasselti was disposed of when a nurse picked it up with forceps and stuffed it in a sharps container. so much for letting science get in on things.)

 

[JaySteel]

Thanks again for your informative reply. I understand the difficulties in accurately drawing conclusions from what little data is available. It's generally accepted that bites from Latrodectus geometricus are not as dangerous to humans as most other Latrodectus species. If the potency / toxicity of Latrodectus geometricus venom is equal to, or greater than, that of other Latrodectus species then can we not safely conclude that the most logical explanation is that less venom is injected during a typical defensive bite from Latrodectus geometricus than from most other Latrodectus species?

 

[The Snark]

then can we not safely conclude that the most logical explanation is that less venom is injected during a typical defensive bite from Latrodectus geometricus than from most other Latrodectus species?

I'd contact Rick Vetter as he has lived and worked in Geo and Hesperus areas for decades. If anyone can steer you to data or advise on taking a survey it would be him.

 

[JaySteel]

OK, thanks.

 

[The Snark]

OK, thanks.

Something to think about. The top 3 people killing snakes are lethal for three different reasons. The krait for how powerful their venom is, the Saw Scale or Russells viper for packing a cocktail of both neuro and hemotoxins and the king cobra whose venom isn't even in the top 50 most potent. Instead, it delivers tremendous amounts of venom. Then mom nature throws a few wrenches more into the works. The krait is docile and can be handled with relative safety most of the time, except from dusk until around midnight. Vipers are vipers. Loaded guns with hair triggers 24/7. O Hannah wants nothing to do with humans and avoids them wherever possible. They cause deaths simply because human and their habitat cross paths so often.
Obviously venom potency is only one factor.

 

[darkness975]

Hi everyone. Having read through the excellent website of @Widowman10, I have a couple of questions regarding the venom of Latrodectus sp.

The LD50 values are quoted by Widowman10 as being:

Latrodectus geometricus = .43 mg/kg (IV) & .223 mg/kg (IP)

Latrodectus hesperus = .84 mg/kg (IV)

Latrodectus mactans = 1.39 mg/kg (IV) & .90 mg/kg (SC)

Latrodectus bishopi = 2.2 mg/kg (could be IP)

Latrodectus variolus = 1.8 mg/kg (IP)

Based on the figures above does Latrodectus geometricus have the most potent venom of the Northern American Latrodectus species, but because the yield of venom is considerably lower than other Latrodectus species the bite of Latrodectus geometricus is not usually medically significant to humans?

Which of the Northern American Latrodectus species is considered to be the most dangerous to humans, taking into account both the potency and yield of the venom? I've read conflicting answers to this question from varying online sources so I imagine opinion varies on this topic.

Thanks for your help.

Give this a watch.

 

[The Snark]

@darkness975 He had more of a reaction than most Latrodectus bites. An epidermal reaction is unusual. Systemic neurological reactions are rare. Both my bites were small mildly painful red dots that might have persisted for a while but I scrubbed them vigorously giving myself an irritated large area for several hours.

 

[darkness975]

@darkness975 He had more of a reaction than most Latrodectus bites. An epidermal reaction is unusual. Systemic neurological reactions are rare. Both my bites were small mildly painful red dots that might have persisted for a while but I scrubbed them vigorously giving myself an irritated large area for several hours.

Part of that is because he intentionally sustained a much longer bite than most.

 

[The Snark]

Part of that is because he intentionally sustained a much longer bite than most.

I confess to zooming through the video. Low tolerance level for deliberate stupidity. I'm curious as to your take on this apparent paradox??

My unscientific impression is Geo is the spider equivalent of a stripped down cheap economy model of a Latro. All about mass production and many of the quality functions missing or compromised.

(Off the topic, check this out: https://www.bbc.com/news/world-australia-63699884 )

 

[darkness975]

I confess to zooming through the video. Low tolerance level for deliberate stupidity. I'm curious as to your take on this apparent paradox??

My unscientific impression is Geo is the spider equivalent of a stripped down cheap economy model of a Latro. All about mass production and many of the quality functions missing or compromised.

(Off the topic, check this out: https://www.bbc.com/news/world-australia-63699884 )

For what it's worth the guy on that channel doesn't do the sensationalist crap for views. He parodies other youtubers (like coyote Peterson) that do. That's why the thumbnails and first minute are so weird but the actual meat is good.

He admits his reaction to the L. mactans or hesperus was more extreme because he sustained a significantly longer and more potent bite than most people would.

 

[The Snark]

I keep recalling a man in Australia that accidentally brought a Hasselti back to bed with him from the outhouse. Bitten multiple times he had to have antivenin administered repeatedly over the course of a year.
Or my bite which developed a wart like growth about 10 years after the bite. A pathologist did a section of it then guessed the neurons had been scrambled and passed along erroneous growth patterns on down through multiple cell replications.

On the whole, not a venom you want to play with.