LD50 Score for The Faint-Banded Sea Snake, Hydrophis Belcheri

Guenter Leitenbauer wrote:

Wolfgang I always thought that Naja nivea is one of the cobras with the most potent venom besides Naja philippinensis. Am I wrong?

Not wrong, just taking LD50s too seriously. You can get 5-10 x differences between venoms of different populationsof the same species, and 5-10 times differences between individuals of a single population.

As an example, there is a paper on variation in venom activity of Argentinian Bothrops alternatus in the current issue of Toxicon. The LD50 of different venom pools to mice varied from 35-174 micrograms per mouse, and the LD50 of individual snakes from one population from 44-116 micrograms.

Those differences are alreday greater than the differences between N. naja and N. nivea in BGF's LD50 tables. It all depends on what particular individual snakes and what populations donated the venom being used in the tests.

Also, it is important to remember that toxicity is not an absolute measure - it will vary depending on what you want to kill. Sydney funnel-web spider venom is highly toxic to humans, but of low toxicity to rabbits. So arguing about which snake species is more lethal (?to humans) because one has a 2 x lower LD50 than the other for white mice is a complete waste of time.

Wolfgang Wüster wrote:

'So arguing about which snake species is more lethal (?to humans) because one has a 2 x lower LD50 than the other for white mice is a complete waste of time'.

I don't know about that... There has to be some method of determining the toxicity of venomous snakes, although I agree that one shouldn't take these LD50 scales too seriously in view of the many factors to be considered that are involved in Human envenomations and the uncertainties of venom composition within individual snakes species. Heatwole discusses some of the variables of sea snake venom as it relates to Humans in Chapter 10(Sea Snakes and Humans)including some brief remarks on Toxicity, Dose Delivered, Human Lethal Dose, Fang Length, Aggressiveness(of the snakes- not the Humans...), etc. In my view, some useful generalizations can be inferred from LD50 scales. Sincerely, Jon Davidson .

Generalities are about all that can be expected from LD50 charts, since venom effects in humans vary so greatly. Some populations of a given species may have a neurotoxic component, while other populations may lack a significant neurotoxic component but may have a strong hemotoxic element. As Wolfgang has pointed out, some venoms are exceptionally toxic for humans, an example of this could be Echis carinatus, a bite which is difficult to treat, and has secondary effects of great clinical significance appearing days after the patient appears to have been improving.

What has, perhaps, the most meaning, is how likely it may be, if someone is bitten, the chance of surviving the accident-and surviving without disability- with, or without treatment. Many people have survived bites but have suffered loss of limb, and some people have died months after the accident despite having had quality medical care. Of course, many people are bitten in rural areas where medical care may be hours, or days, away. This contributes to the high number of fatalities given for species such as Bitis arietans, the Puff Adder, or Daboia russelli, Russells' Viper.

Notechis scutatus, the Australian Mainland Tiger Snake, has an extremely potent venom, but accidents in the wild are uncommon with most bites occurring to people collecting or handling the snake in captivity, and access to antivenin is typically available within a reasonable period of time. Recovery with medical care would be expected, while a bite from Bitis gabonica, the Gaboon Viper, a snake with a relatively weak venom compared to Notechis scutatus (LD50, 12.5 vs. LD50, 0.214, http://www.venomdoc.com/LD50/LD50men.html) could result in death weeks or months later due to renal failure.

Some species have a very high percentage of deaths even with antivenin therapy, Bungarus caeruleus, the Indian Krait comes to mind as one such species, although this may be due to untimely medical treatment. In addressing the question of which species pose the most danger to people who are bitten, perhaps the best approach would be along these lines, that is, percentage of deaths following timely, competant, medical interaction.

Oxyuranus microlepidotus, is regarded as the most venomous snake in the world (Pers. Com) of Dr. Bryan Grieg Fry et,al. venomdoc .

http://www.kingsnake.com/toxinology/venomdoc/Scientific_publications_files/2005_BGF_Oxyuranus_natriuretic_toxin.pdf

Thank you all, for your participation in this subject, regarding the age old question of the Dept.,of toxinology in snakes.

Sincerely,

Albert.


Addtl. for those interested the article is numbered 25# on the reasearch dept. of venomdoc.

Wolfgang, I agree of course. This artificial LD50 hype from Mr M. is a tedious waste of time. What i meant was:

It is hard to believe in the relevance of these LD50 when those imply that Naja naja is more venomous than Naja nivea.

Too many parameters with snakebites as some pointed out. And we technicians say: "You can fit any curve, even a micky mouse, with enough parameters."

good book that. each time i flick through it i wish we were allowed to keep these local beasties legally.

Jack , Nigel Sowter has the perfect set up for them too,

Concerning LD50 values derived from laboratory mice:

When for those snakes for which there is sufficient info in the form of human bite cases, the clinical reports are compared with the results of LD50 studies, there is typically a correlation, although by no means a perfect. For instance, by and large, bites by many of the notorious elapids are more often life-threatening than bites by viperids, and grossly, elapid venoms are further up on the LD50 lists (equivalent to lower values = higher toxicity; see Brian's homepage for info). However, having said this, it is also very clear that there are very notable exceptions. The reasons for this are manifold. Firstly, LD50 values are only as good as the research lab that performed them and in particular, as the collectors that collected the snakes and pooled the venom (misidentifications and mixtures are thought to be not uncommon). Then there are the handling and storage of the venom, and the injection into mice of different sources and through different routes not always performed by routined staff, etc. All this of course forces us to take all LD50 values with a grain of salt. Lastly, even if the values are determined in a reasonably standardized and relyable way, there are of course great differences in the venom toxcity to different species from different genera or even order of test animals. This has long been known and is documented in many publications. One good recent example is a paper from Steven Aird and colleagues on the LD50s of venoms from the genus Micrurus. Here the differences in toxicity (measured by one and the same lab) varied easily 10-fold or more between the different test animals with, no wonder, the 'natural' prey animals being the most vulnerable. In the end, we are confronted with several interesting cases suggesting that some venoms are much more toxic to humans than to lab mice. For example, the LD50s of the whole venom from the bushmasters as determined in lab mice is so high indeed (low toxicitiy) that many of them should never cause any serious health problems given the amount of venom they produce, yet many fatalities are on record. It just seems that humans often react to Lachesis venom with life-threatening circulatory collaps. So here, LD50 values are misleading. Likewise, the subcutaneous LD50 of the venom from the Clarence river snake (Tropidechis carinatus; short fangs) has been determined in mice as approx. 1,2 mg/kg. Given the small amount of venom that can be milked from these snakes (typically just a few milligrams), Tropidechis would hardly qualify for a highly dangerous species. However, fatalities are on record, and the snake is considered un par, in terms of toxicity, with the tigersnakes. Indian kraits show a much lower toxicity to mice than taipans, yet the case fatality rates in humans are essentially the same. Several other examples exist.

So in the end: Yes, LD50 values are useful to some extent, but they certainly cannot be linearly extrapolated to provide info on the effect of venoms to humans of a given body weight. What is really needed is a more complete report and careful evaluation of human bite cases.

Klaus, you have excellent writing skills and show an exceptional form in the delivery of your message.
i almost feel bad about bringing this subject (LD50) up , perhaps it should have been an PM but to whom ? no body talks about anything an even less heated topics as these.

Here The United States Of America and perhaps every where some Herpetoculturist and Herpetologist are very educated and perhaps a little off center there are PHD's who drive trucks , Cuban doctors who work at the Ritz Carlton (Key Biscayne, Miami ) as banquet waiters at one thousand dollars per night, and fifty year old reptile enthusiast's who listen to rap music all day JZ, lil Wayne, etc.

So yes maybe the topic was off center i apologize if any one was offended , yet there is one circumstance you left out, thats rapid evolution of venoms in hemotoxic / neuro toxic snakes in particular a Crotalus group of the Southwestern United States.

A North American member of Venomland , curator and PHD has been conducting a study on the rapid evolution of venom (5 years time) insitu on certain Rock Rattlesnakes of this hemisphere and has deducted that the reversal of hemotoxicities to high neurotoxcities is due to habitat destruction and forcing these specimens to adapt and find prey that is not in their natural diet.

The rates of neurotoxicity is so high that it may change the LD 50 score standing of all previously discussed specimens.

Thanks for the reply i have no further comment on this subject until the author decides to make his discovery public.

Regards ,

Albert.

(obs.) i agree with your complete statement.

Albert, no reason to apologize! Glad you brought this topic up. In our field there is a lot of misunderstanding out there, but in the end, my guess is as good or bad as that of anyone else. And who knows what future research will reveal.

Best,

Klaus