You cannot poison an opossum

As we established last week, biology is freaking crazy.

Here's more proof. For this, you don't even need to go to exotic Australia. The common American opossum produces a protein called Lethal Toxin-Neutralizing Factor (LTNF). This protein does pretty much what the name implies—seeking out potentially deadly poisons and neutralizing them. The benefit: Opossums are all-but immune to the venom of poisonous snakes. (Including the venom of snakes native to continents where the common American opossum does not live.) But it gets weirder, as Jason Bittel explains on the BittelMeThis blog:

So they took some rats and injected them with LTNF, then pumped them full of otherwise lethal doses of venom from Thailand cobras, Australian taipans, Brazilian rattlesnakes, scorpions and honeybees. But the rats just laughed in their faces.

“Dude,” said one scientist, “we have to kill these rats. Do you watch AMC’s Breaking Bad?” The other scientists nodded of course because everybody watches Breaking Bad. So next they tried to kill the rats with ricin, an extremely lethal poison made from castor beans. (How lethal? Just ask Georgi Markov, the real-life Bulgarian defector killed by a ricin umbrella gun. That’s right, I said ricin umbrella gun.)

Alas, the ricin was a no-go. The now-snooty rats danced Ring Around the Rosie.

“That’s it!” screeched the lead scientist. “It’s time to release the botulinum toxin. Surely this will conquer the awkward opossum’s super serum!” But after many maniacal laughs and a few bolts of lightning, the rats were still alive.

(The paper does not mention what became of the super rats. I can only assume they went on to write “The Secret of Nimh” while the evil scientists lost their rat-killing grant.)

Read the research paper

Read the rest of Jason Bittel's story on the strange and wonderful biology of opossums.

CORRECTION: This post originally referred to echidnas as marsupials. This is incorrect. They are monotremes. The editors apologize to any monotremes, marsupials, or zoologists who were offended.

Image: Jesus and the 12 Opossums, a Creative Commons Attribution Share-Alike (2.0) image from mollyeknox's photostream


  1. Why aren’t we trying to use this in humans instead of stupidly expensive rattlesnake anti-venoms that are so expensive we’re not necessarily having them in stock close enough to save lives from the bites.

      1.  I Am Not A Rat. Not everything that works in rats works in humans, due to humans not being rats. It’s one of those annoying things about the rat model ;)

    1. Given that 0.000027 percent of the US population is bitten annually, prevention seems like a waste of time.

      1. If LTNF turns out to be equally effective in humans, then that proportion will rise signficantly as we lose our fear of venomous snakes.

        1. It’s apparently extraordinarily difficult to get a rattlesnake to envenomate you. People poked at them, even stepped on them without a response. The only way to get a bite was to pick one up, and even then, you get dry bites.

          1.  I think it depends greatly on the disposition of the individual snake, some mellow and some “just a bit bitey” croc hunters words for the snake that is ravenously striking at everything.

    2. Science is methodical and is especially cautious (and bureaucratic) when it moves from the lab to the clinical setting.  One slow step at a time.

      1. I just noticed that the paper was written in 1999.  The process is even slower than I thought . . . we need an update on the research

        I can’t find the paper or the journal it was published in, nor much of anything else on the subject, in PubMed.

  2. i don’t watch breaking bad.  i have enough hobbies, and i hear meth takes up a lot of time and money.  can someone fill me in on the reference here?

      1. Could have been a reference to the bathtub/basement sequence from the first season (because the guy in the basement had seen their faces, and had to be killed).

    1. spoilers:  ricin is a major plot point in season 4. sidekick carries a ricin-spiked cigarette,and henchman swipes it from him,and they use the old reddit switcheroo to make him think that’s how a kid got poisoned, but it was really from a flowering plant. sidekick had the ricin, which they made from castor beans, as a plan to kill the big boss, but he either chickened out of never got a chance to use it. BB is the best show i’ve seen in years. Better than the guild, better than black books, can’t think of anything comparable. season 5 starts in 4 days.
      – arbitrary aardvark

    1. The last part of the article says no, but they can heal very quickly.  Meet the newest member of the X-Men.

    1. No, it was a gun. It used compressed air to shoot a metal pellet into his skin, not a needle to inject a liquid.

      1.  it had a needle at the tip of the umbrella that injected the pellet in to the back of Georgi Markov’s leg. It was designed so that the injection would look like someone just accidentally bumped in to him.

      2. Surely the quiddity of gunniness includes the penetration of a surface and the delivery of material into the target. Wheras syrinxiness includes only the delivery without necessary penetration (like a cake-icing syringe).

        Oh. Glue gun.


  3. Sorry, Maggie, but your echidna is a monotreme, not a marsupial!

    Some parts of the Internets have told me that the opossum is highly resistant to the rabies virus, possibly because its body temperature is lower than non-marsupial mammals, thus impeding the spread of the virus through the nervous system and giving its immune system more time to respond.  But this sounds rather hogwashy to me, and I can’t find convincing proof anywhere.

    You could totally make up for the monotreme/marsupial confusion by getting to the bottom of this!

  4. This is an enhancing that definitely needs to be available for my next genome upgrade. I hope one day it is going to be as common as vaccines are today. And before naysayers come, vaccines were mistrusted for a long time, and still today.

    1. welcome to the world of cheap and “safe” consumer goods.  what kind of shampoo and pharmaceuticals did you use in your previous parallel-universe/shipwreck-island?

  5. The sad part is that this paper is from 1999 and the author “patented” LTNF in 1996 :
    LPPS, BV., LIPPS, FW. Embodiments of natural and synthetic lethal toxin neutralizing factor and their utility as treatment for envenomation. US patent, 1996, 5, 576, 32. 

    So my guess is that this could have bee unavailable many year a go but they are still figuring out how to make money out of it. Or some pharmaceutical bought the patent and then figure out it could not make enough money and buried.  This is why patent on genes, peptides, etc makes no f@#!$g sense. 

    1. They could also be working on a clinical trial for it.
      Who knows, they might have found out in Phase I that small amounts kill people.

      Also, in order to test LTNF for its efficacy (in defeating poisons) they would have to have a study population that was getting bitten or subjected to venomous injections…
      I would love to read the Informed Consent Form on that one:
      “As a subject in this trial you will be randomly injected with snake venom…. or a placebo” and then LTNF to see if it works.
      Possible side effects include death.

      1. Especially tricky in the case of necrotizing venoms.

        The ones that float merrily through your bloodstream and then poleaxe some vital CNS or respiratory component are the ones that will kill you good and hard without treatment; but they are also the ones that can be best treated by a suitable antivenom also floating merrily through your bloodstream(and possibly mechanical ventilation until things work themselves out).

        The ones that hang around at the bite site, killing chunks of tissue, aren’t going to kill you except by secondary infection; but you’ll have quite a nasty little wound even with antivenom available.

  6. What I find fascinating is that there are two Opossum rescue/information organizations in the US: the National Opossum Society and the Opossum Society of the United States, both founded by Dr. Anita M. Henness. As far as I can tell, a schism formed over the correct diet for opossum rehabilitation.

    1.  yes im from oz an i believe our possums have migrated to nz to balance the influx of you guys here ;)
      just kidding!  but possum != opossum. i dont think the oz possum has the same toxin immunity. or if they do, its not widely known in oz

  7. Say I lived in an area where possum was eaten by folks, includin’ myself.  Could I go to church every Wed. and Sun., handle poisonous serpents, get bit and not be killed?  I’m partly joshin’ but partly posing a legitimate question.  No, I don’t eat possum.

    1. Digestion tends to screw up protein of all kind, that being its job. So does cooking, that being ITS job.

      So, no, highly highly unlikely.

      You are not what you eat, or you would be a basket of wheat and a cow (modify according to diet).

  8. Or go to church every Wed. or Sun.  Have been known to pickup a Copperhead every now and then,

  9. Try some Warsaw Pact grade binary nerve agent. I’m sure it’s been tried and since they still issue MOPP gear to the army I’m going to suppose it won’t stop the really nasty stuff from the 20th cen.

  10. Hmm…I wonder what  would happen if they were given large doses of Lithium.  I’ll bet that would bypass all the other toxin defences, or at least give them Akasthesia.

    1. What I’ve been thinking since I’ve heard this story: “How do you define poison?”  For example, if you gave them a giant dose of iron would they still survive?  If you fed them digitalis (fox glove) would their hearts not stop?  If you filled them with polonium would they still live (although rats are not a good test subject for testing radiation effects, they were found living in the dirt at several ground zeros in the Bikini atoll)

    1.  I was hoping SOMEBODY would recognize my paraphrasing of one of the funnier moments in Breaking Bad.  Probably only surpassed by “A robot?” or “Ohhhh…wire.”  Note all feature Jesse.

  11. I do wonder what it is with science that gets those literary juiced flowing. I keep bumping into colorful descriptions of events as far afield as rocket engines and rat poison…

  12. Of course you can poison an opossum.  Just give it a transfusion in which you replace all its blood with poison (or any other non-blood substance). Chances are it’ll die before all its blood is replaced. Not that I’m advocating this.

  13. Not to take anything away from opossums, but I think this research might be… well at the very least exaggerated. First, the author has something to sell, that should always be in the back of ones mind. Second, it seems that the author has a small peptide derived from this protein, which, if true, would be very easy to verify. The paper looks very fishy to me. I work on bacterial toxins at the moment, I can tell you that I would be ecstatic if I had something like this in my hands. My career would be done. I would be famous. And believe me, many companies/investors would be very happy. The reason I am suspicious, is mostly that these toxins are quite different from one another, so it is hard to imagine that a single agent would work perfectly against all of them. Now, if someone replicates this and see the same results, I will be more optimistic. Right now, it just looks like snake (oposssum?) oil to me. 

    1. Bast, that’s an excellent point that should be part of an UPDATE to Maggie’s post at the top.

      If this is accurate, it would be revolutionary.  Maybe the paper in question exaggerates.  We won’t know until we see if it’s been duplicated elsewhere.  What further work has been done here?

      It seems the author, Binie Ver Lipps, was an Indian woman who died in the US (Texas?) in 2010. There’s an online obituary here:

      Some of her books are here:–zzBinie+Ver+Lippsz200000zB6z5—html

  14. So if Possums have this super power, are they related to Mongooses (Mongeese? Mogoosi? WTF is plural of Mongoose?) 

    Aha! I knew Sonic the Hedgehog had super powers too. See

        1.  Ok, now you’ve done it…I can’t get the Herpestidae Psittaciformes hybrid out of my mind! “Side-order of cobra to go with your crackers sir?”

        2. Mongeese. Usage, “a mongaggle of Mongeese.”

          “What’s good for the mongoose is good for the mongander”?


  15. “exotic Australia”.
    Exotic? Really?
    We’re English-speaking, like you, yanno. We are a democracy, like you, yanno.
    And btw, why don’t your comments show up in Opera? Very poor form, IMO.

    1.  I think she just meant that the animals of Australia are exotic.  Australia is famous for having lots of very poisonous snakes and spiders, for example.  Many of Australia’s native species are unusually distant from other species in degree of relatedness because of the continent’s geologic isolation.  You can’t find anything like a kangaroo in Kansas.  The closest thing to a kangaroo in Kansas, actually, is an opossum–the only marsupial species left in North America.

    2. Yeah, from a flora and fauna perspective, y’all are about as exotic as it gets. Also from a poisonous/deadly creatures perspective. And you once lost a Prime Minister to the sea. Speaking as a landlocked North American, all of these things sound pretty exotic. 

  16. “The other scientists nodded of course because everybody watches Breaking Bad. ”
    Wrong–I don’t! 

  17. Well, unfortunately no-one’s going to read my comment among all the rest, but sadly, you CAN poison an opossum.

    I live next to a wooded area that is surrounded by auto garages. I encounter sick and dead opossum all the time. I have taken the sick ones to the wildlife rescue, and they try to nurse them back to health with Pedialyte. They say the opossum are drinking antifreeze-contaminated water from the pavement and ditches. It’s slow acting, and the healthy-looking opossum simply becomes lethargic, lays down and dies.

    On a similar note, please don’t try to control pests with poison. They are ALL slow-acting, and the animals suffer for days or weeks before they die. Additionally, other predators can eat them and become sick themselves. Pests can be trapped and relocated. If it’s illegal in your area, you may be able to hire someone with license to do it for you.

Comments are closed.