This question is prompted by an incident recounted in the book Jaguar: One Man's Strugle to Establish the World's First Jaguar Preserve by Alan Rabinowitz.

The author, with several assistants, was attempting to capture and collar a jaguar in the jungles of Belize in the mid-1980s, when one of his assistants was bitten right above the ankle by a fer-de-lance. They had left the anti-venin in their truck because they thought they would be hiking in only a short way, so it was more than 45 minutes after the bite before another man arrived, running, with the anti-venin. The pain had moved into the victim's thigh, and was intense.

Although the situation was critical, the antivenin [could not be administered] immediately. It was made with horse serum, and a person first had to be tested for a possible allergic reaction to the serum. Failure to do so could cause death from the serum alone.

The test took 15 minutes, so it was an hour before the antivenin was administered. By this time, the victim's calf was swelling and he had started bleeding from the tongue. It took another 4 hours to get him to their camp, where a plane was waiting to evacuate him to a hospital in Belize City. Despite more antivenin, the victim died. This was in the mid=1980s, and the hospital was not state-of-the-art.

Question: Given the time already elapsed, and the remoteness of the area, might it have been advisable to administer the antivenin as soon as it arrived, dispensing with the allergy test? My reasoning is: If the victim was allergic, the antivenin could not be administered, and the victim would die. If the victim was allergic, he might die from the reaction. But the antivenin might save him.

I know second-guessing is easy to do and hard to get right. I am asking for a knowledgable critique (not an opinion based criticism) of the reasoning. And: What has changed in the past 40 years in treatment of venomous snake bite? Are anti-venins still made with horse serum?

Additional Information, based on reading further in the book: The hospital, despite lacking a working antivenin intravenous drip, apparently stabilized the patient with further antivenin injections, keeping him awake (although they later sedated him), draining the fluid buildup, and giving him blood and glucose. However, his wife arrived, checked him out of the hospital and turned him over to a rural "snake doctor" (they were indigenous Mayans); the victim died a day or two after this.

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    More likely to have an epi pen with them now than 40 years ago. It is also conceivable that the victim knows they are allergic to certain things, so asking them may reveal knowledge. But, hours from help, you make the best decision you can come up with and proceed from there.
    – Jon Custer
    Commented Feb 6 at 13:37
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    If you are in a situation where you are remote and have anti-venin for a specific snake you should already know when to administer it, and what the contraindications are. The same applies to ANY medication you have while in a remote setting. With wilderness medicine your first-aid kit should only contain items which you have the proper knowledge of their use.
    – noah
    Commented Feb 6 at 18:55
  • I'm not knowledgeable about the use of anti-venin, but can speak to administering specialized medications more broadly in a USA wilderness context. Trained medical professionals open themselves up to liability if they administer medication outside their scope of practice. First doing the allergen test might be a required part of the scope of practice for anti-venin at the time. In which case, even if doing so would be well intentioned, many medical professionals will not operate outside their scope.
    – noah
    Commented Feb 6 at 18:59
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    After some googling around, I find that the death rate (untreated) of a fer-de-lance bite is somewhere in the region of 6-10%. I'll add more from a fairly recent journal article below.
    – Jon Custer
    Commented Feb 6 at 19:04

1 Answer 1


As noted by @bob1 in the comments, the snake in question was likely Bothrops asper in the OP's incident, not Bothrops lanceolatus that the journal article here is about. But I'll keep this bit, and add more below.

A 2010 article in the journal Toxins, here linked through NIH focuses on data from Martinique where there are some 20-30 bites a year. In the conclusion they state (I've bolded a few relevant bits):

Bothrops lanceolatus, notoriously named “Fer-de-Lance”, is the only endemic snake in Martinique. It is responsible of about 20-30 declared bites per year. Envenomation generally leads to swelling and pain, while occasionally, systemic signs and/or coagulopathy may appear. Severe multifocal vascular thromboses may result in life-threatening symptoms leading to permanent disabilities or death. An equine monovalent antivenom serum (Bothrofav®) was shown to be safe and effective for the treatment of B. lanceolatus bites when used within 6 hours. However, in recent cases, thrombotic stroke occurred despite antivenom early administration, questioning the necessity to obtain an improved antivenom.

Further, in a table on dosing of the antivenom they mention in a note

Potential allergic reaction should be considered in all patients.

In addition, as noted at A-Z Animals,

The death rate for people who do not receive anti-venom after they’re bitten by a fer-de-lance is about 7 to 9 percent. But even if you don’t die, the bite can cause such severe necrosis in a limb that you may need to get that limb amputated.

Taken all together, and considering my WFR training:

  1. I'm not qualified to provide antivenom to begin with. The section on snake bites in my WFR (Wilderness First Responder) training does not include antivenom. Perhaps I could be certified somehow if traveling to a specific area. If on an expedition with the antivenom there should be protocols for carrying and dispensing.
  2. The actual risk of death is fairly low, although the patient may well feel otherwise. The protocols likely would mean that trip members would have provided their possible allergic reaction to the antivenom before setting off.
  3. The note in the table on dosing indicates allergic reactions should be considered. Without delving deeper into the antivenom documentation I take that as a medical provider shall at least ask about the potential for a reaction. Any way, I know my training doesn't allow me to administer the antivenom.

But, yes, it seems the antivenom is still equine based, so allergic reactions are still an issue.

And, no, the time taken to determine an allergic reaction was not a limiting factor in the treatment, given the 6 hour treatment timeframe in the article. That determination added 15 minutes onto the 45 minutes, so the antivenom was given within 1 hour.

For Bothrops asper, there is an article by David L. Hardy, Sr. in Biotropica 26(2) 198-207 (1994) titled "Botrhops asper (Viperidae) Snakebite and Field Researchers in Middle America". The abstract starts:

The problem of pitviper bite in field researchers working in Middle America (Mexico to Panama) was studied using case histories of nine biologists and one project employee bitten during the period 1980 to 1991. All snakes involved were Bothrops asper. Based on local tissue and systemic effects, seven cases were severe, three with permanent disability. There were no fatalities. Although antivenom was administered intramuscularly as field treatment to seven victims and later intravenously as hospital treatment to nine as patients, its effect on outcome was uncertain. Nevertheless, intramuscular antivenom is recommended following an adult Bothrops asper bits when tere are signs of envenomation and travel time to a treatment facility is more than four hours.

A paper in Toxicon (https://doi.org/10.1016/j.toxicon.2009.07.001) from 2009 notes that of some 130,000 to 150,000 snakebites per year in Latin America there result some 2300 deaths.

I don't think there is much difference between the results for the two snakes.

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    Good answer. The snake in question wasn't actually the Fer de Lance (Bothrops lanceolatus), as the sanctuary is in Belize, it is a closely related snake B. asper, the only one found in the locality. The antivenin in that article is only available since 1993, so not the same one as administered, which means different efficacy - it is specific for B. lanceolatus too. B. asper might be treated with PoliVal-ICP, but I can't find any data on clinical efficacy.
    – bob1
    Commented Feb 6 at 20:44
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    @bob1 - oh dear, I may have to dig some more to see if there is better info. Thanks.
    – Jon Custer
    Commented Feb 6 at 21:00
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    It looks like various formulations of PoliVal have been made since the 1950s, so it'll be very hard to dig out anything relevant to the timeframe, and I can't see anything on Pubmed that gives any clinical data. The product sheets are all in Spanish, but the one for health professionals says this: In addition to immediate adverse reactions to serum application antivenom, in a high percentage of patients treated with this product Serum sickness occurs and appears between 7 and 14 days after the administration of the antivenom... Doesn't give figures on risk, so might not be the same antiserum
    – bob1
    Commented Feb 6 at 22:19
  • Interesting quote - IM is usually contraindicated in these snakes because of coagulopathies from the toxins in the bites. IM route is slow compared to IV and would only deliver a proportion of the antitoxin too. I wonder if this has changed in the past 20 years to only IV?
    – bob1
    Commented Feb 6 at 23:13
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    @bob1 - in the field you probably don’t have the resources to do an IV.
    – Jon Custer
    Commented Feb 6 at 23:48

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