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Pontifications on Poison

Being some ramblings on events associated with poisonous plants.

Saturday 8th October 2011

Australian newspapers have been reporting a growing death toll amongst horses recently relocated to a property in Kooralbyn, Queensland. Initial reports said that five horses had died but that tally has grown and, as I write, stands at seventeen with an eighteenth animal seriously ill and thought to be unlikely to survive.

So far, the Hendra virus that has already killed over twenty horses in Queensland, this year, has been eliminated as the cause and post mortem investigations are being undertaken to see if a toxin of some sort can be identified. Since the animals had not been on the property long it seems possible that either a toxic plant had been growing in the pasture but all possibilities are being explored include malicious intent.

Oenanthe crocata, hemlock water dropwort

Oenanthe crocata, hemlock water dropwort

These sort of poisoning stories, mostly to do with animals but occasionally involving human deaths, are, of course, unfortunate for those directly involved but they are of interest to me. All too often, however, while the incident makes the news the result of what can be lengthy investigations often doesn’t.

In May last year six people died and another seven were taken seriously ill in the Xinjiang Uygur autonomous region in China after reportedly eating 'herbs' thinking they were celery. At the time, I speculated that, based on the limited information in the reports, it could have been Oenanthe crocata, hemlock water dropwort, that had caused the poisoning. Whatever was discovered about the incident was not reported prominently enough to come to my attention so I don’t know if my speculation was accurate or ridiculous, though I’d bet on the latter.

In 2009, on a ranch near San Diego in the USA, 23 horses were thought to have been poisoned after someone broke into their stables during the night and put Nerium oleander leaves into the stalls. The report I saw said that one horse was seriously ill but responding to treatment while the others seemed to be unharmed. I would love to know what was discovered about the incident but I can’t find any reports beyond those published immediately after.

The more recent poisoning of a zoo giraffe has also dropped off the radar without any further information on whether the zoo went ahead with its plan to remove all the oleander from its perimeter and, if it did, what has replaced it.

Nerium oleander

Nerium oleander

There was one large incident where the outcome was published. In April 2009, twenty-one Venezuelan polo ponies attending a competition in Florida died resulting in speculation about foul play and political intrigue. It emerged, ten days after the deaths, that a pharmacy had been asked to replicate a proprietary dietary supplement and, whether by error or as a result of receiving the wrong instructions, the resulting product contained a massive overdose of selenium.

Selenium is one of those trace minerals that most mammals need to be healthy but in any amount other than ‘trace’ they become lethal. It’s the situation we see with plants all the time. Small amounts can do good but larger amounts become very harmful if not deadly.

I shall be keeping a close eye on the situation in Queensland to see what the investigations come up with as the cause of the deaths.

As a follow up to my 9th September blog entry about a horse in Hertfordshire dying after eating acorns, I saw a piece in Horse and Hound magazine warning owners that the weather conditions have been ideal for oak trees this year and, as a result, there is a bumper crop of acorns. The piece offered advice on how to prevent poisoning and reassurance that such poisoning is rare. I just wish that coverage of Jacobaea vulgaris, common ragwort, was as measured and sensible.