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Swainsonine: It’s Locoweed, not Heroin

Crazed sheep die ‘like heroin addicts’

Sheep by MiqsPix via Flickr (CC BY 2.0)

Sheep by MiqsPix via Flickr (CC BY 2.0)

That’s the catchy headline of a recent article about mass sheep poisonings, and the full article can be read here. It’s meant to entice the headline reader to click through to read the article. I get it. Journalism, however you want to define it, is a business. And businesses such as these need readers. The problem with this headline is that it has nothing to do with heroin – despite the quote from the rancher that led to the headline – and the fact is the sheep did not die a heroin overdose-like death. So even though we are talking about sheep, it can give uninformed readers impressions about those that do succumb to heroin addiction with quotes such as “bashing their heads open ‘like heroin addicts’.”

Heroin addicts look like you or me, in all shapes, sizes, colors, ages and genders. While I am not an expert in drug addiction – I’m an expert on the death side of things – I can guarantee you heroin addicts aren’t bashing their heads open. People that die due to heroin, or other opiate/opioid, intoxication primarily do so via respiratory depression and pulmonary edema (1). It can be a quick death, or a slow, lingering one. The tolerance to respiratory depression is much slower to develop than tolerance to the euphoric effects, thus experienced users are usually more at risk of overdose. Either way, the victim is usually unconscious and unaware of their dire situation.

Darling Pea by David Lochlin via Flickr (CC BY 2.0)

Darling Pea by David Lochlin via Flickr (CC BY 2.0)

But I do want to talk about this story, as it highlights another of Nature’s Poisons, and a serious issue for ranchers. Following a brushfire in the Warrumbungle National Park located in New South Wales, Australia, the poisonous “darling pea” took over and led to the death of 800 sheep. The darling pea, Swainsona galegifolia, belongs to the Fabaceae family, which is commonly known as the legume, or bean, family. If you think about all of the different peas and beans in society, you can see how important it is to the economy and diet of billions of people.



But that’s not the darling pea. The darling pea is vicious and has a negative economic and dietary impact. All of this is due to a simple chemical made by the darling pea: swainsonine. I say it’s simple, and it is if you’re a plant, but if you’re a synthetic organic chemist in a lab you’re looking at 12-15 steps and multiple chiral centers to contend with – it’s a challenge, but so much fun (2, 3). Swainsonine inhibits glycoside hydrolases – enzymes that hydrolyse (break apart by adding water) glycosidic (sugar) bonds. Easy, huh? And you thought biochemistry was hard. These enzymes are important because they break down complex carbohydrates into simple sugars. Inhibition of this enzyme leads to the build up of carbohydrates in the cell, resulting in cell death.  Additionally, the hydrolases breakdown glycoproteins into – you guessed it – proteins and sugar. An accumulation of glycoproteins interferes with cellular communication in the nervous system, which gives rise to the clinical symptoms of swainsonine poisoning (4).

Many symptoms of swainsonine poisoning resemble those of chronic alcohol intoxication, which if you want to get technical is also a poisoning. The symptoms include: sluggish gait, depression, weight loss, a staring gaze, and general uncoordination (4). [In the United States, any swainsonine containing plant is called “locoweed”, which clues you in to its actions.]  The effects on the nervous system is permanent, and the animals never fully recover. If chronically poisoned, livestock may experience infertility, abortion, cardiovascular disease, and death (4). But it’s not just the darling pea grazer that is affected. Pregnant livestock that are poisoned will give birth to babies with skeletal deformities. So not only is the current generation affected, but the next as well.

It is easy to see, now, how drastic this is to the affected Australian sheep ranchers. They lost over 800 sheep, and with decreased libido in the males, possible abortions in the females, and birth defects if they do deliver, the effects will be seen for years, with a huge economic impact. The totality and severity of the situation doesn’t need an inaccurate and misleading headline, just a straightforward and honest one. The sheep deserve it.

Thanks to John Robertson of The Poison Garden for bringing this article to my attention.

*** Homepage featured image of darling pea by David Lochlin via Flickr (CC BY 2.0) ***

1. White, Jason M., and Rodney J. Irvine. “Mechanisms of Fatal Opioid Overdose.”Addiction 94.7 (1999): 961-72.
2. Wardrop, Duncan J., and Edward G. Bowen. “Nitrenium Ion-Mediated Alkene Bis-Cyclofunctionalization: Total Synthesis of (−)-Swainsonine.” Organic Letters 13.9 (2011): 2376-379.
3. Louvel, Julien, Fabrice Chemla, Emmanuel Demont, Franck Ferreira, and Alejandro Pérez-Luna. “Synthesis of (−)-Swainsonine and (−)-8–Swainsonine by the Addition of Allenylmetals to Chiral α,β-Alkoxy Sulfinylimines.” Organic Letters 13.24 (2011): 6452-455.
4. Cook, Daniel, Michaelh. Ralphs, Kevind. Welch, and Bryanl. Stegelmeier. “Locoweed Poisoning in Livestock.” Rangelands 31.1 (2009): 16-21. 

3 thoughts on “Swainsonine: It’s Locoweed, not Heroin

  1. Pingback: The Sheepening | Weetje van de Dag

  2. Pingback: There’s More Than One Way to Kill a Fish | Nature's Poisons

  3. Pingback: Of Djenkol Beans and Djenkolism: The Southeast Asian Delicacy that Poisons | Nature's Poisons

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