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Pontifications on Poison

Being some ramblings on events associated with poisonous plants.

Saturday 3rd March 2012

I’ve been keeping an eye on reports from Tennessee of the deaths of seven horses in Maury County. As usual, the initial reports contained speculation about what might have caused the deaths and I have been waiting, in vain so far, for any follow-ups.

The initial reports spoke of seven horses dying on a single farm and noted that three other horses on the same farm seemed to be perfectly OK. Not surprisingly, within days it was being reported that other animal deaths in the area were being investigated to see if they were linked.

I’m sure that is an example of Red Nissan Micra syndrome. Farm animals die. In this area, the unmarked red and grey trucks used to remove dead farm animal carcasses for disposal are a regular sight so it is no surprise that a number of other deaths occurred in the area surrounding the Maury County farm where the seven horses died. And, as expected, there has been no suggestion that there is any link between them.

The deaths occurred on 12th February and, because there were no physical signs of harm, samples were sent for analysis to see if some poison was responsible. On 23rd February, the same day the other deaths in the area were being brought into the story, the results of those tests showed no signs of any toxin.  

The causes of death, therefore, remain undetermined and it was said that they could, possibly, have resulted from the animals eating a poisonous plant or contaminated hay. And that is where the story, so far, rests. I’ve seen nothing to indicate that further more detailed tests are being done given that the short time between the incident and the announcement of the results of the testing indicates that full toxicological screening wasn’t undertaken.

Jacobaea vulgaris, common ragwort

Jacobaea vulgaris, common ragwort

Thinking about horse deaths possibly from a poisonous plant with an unfinished story reminded me with that the story of the British Horse Society’s survey of Jacobaea vulgaris, common ragwort, remains unfinished.

I went looking to see if the results of that survey had, yet, been published and was surprised to discover that the survey was still open for people to complete. I decided to have a look and see just what data the survey was seeking to collect. I’m involved, at the moment, in a proposal to undertake a survey of users of a facility (nothing related to this site) and a lot of our discussions have been around survey design. A key element of conducting surveys is to ask enough questions to get reliable information without making a survey too long so people either give up or don’t think about their answers.

The BHS survey turns out to be extremely short; it actually consists of only four questions making it very difficult to collect reliable data.

Before you get to the first question, it is made clear that this is aimed at only those people who have seen ragwort. Immediately, this makes it impossible to get any idea of overall prevalence. A lot of people claim that the amount of ragwort is increasing. With no attempt to identify how many people see ragwort and how many don’t, the BHS survey does nothing to test that claim.

The first question asks the type of land where the ragwort was seen. That is very significant because it jumps over the whole question of whether the survey respondent can correctly identify ragwort. Actually, it is worse than that because it is only common ragwort that is subject to the 1959 Weeds Act and there is no attempt to determine what sort of ragwort the respondent has seen if, indeed, it is ragwort at all.

We’ll have to wait and see what the BHS does with its survey data. Last year, the main use of the 2010 survey was to publicise the launch of the 2011 survey, which publicity led to a lot of ill-informed reporting in the media. As a responsible body, I’m sure the BHS will want to prevent a recurrence of the almost hysterical reactions that came from some quarters.

It may seem an odd time of year to be writing about Jacobaea vulgaris (still, often, referred to as Senecio jacobaea) but the mild winter seems to have brought many plants out early and I’m already starting to see threads about ragwort on internet forums often with the usual misinformation.