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Pontifications on Poison

Being some ramblings on events associated with poisonous plants.

Monday 24th November 2014

There’s one point that must be included in every media training course for politicians. That’s the non-hysterical start that I favoured over the more hyperbolic ‘The first rule for politicians when dealing with the media is…’ I don’t actually know at what point it will be included in the course but I’m sure it is there.

It is the exhortation to not accept the premise of the question. If a journalist asks what the politician intends to do about the situation in Freedonia giving any answer simply confirms that there is a situation in Freedonia when there may not be.

The British Horse Society has published the results of its summer survey into Jacobaea vulgaris (syn. Senecio jacobaea), common ragwort, and some people have tried to argue with the numbers the survey has thrown up. I think that is a mistake because, it seems to be, that accepts the premise that the survey was capable of generating numbers that are worthy of evaluation.

Jacobaea vulgaris (syn. Senecio jacobaea), common ragwort

I want to argue that the survey’s questions were so badly structured (and there is always the chance this was entirely deliberate) that there is nothing to be gained from considering the results.

The first and most crucial point is that this was a self-selecting sample. Anyone who had an interest in the relationship between horse and ragwort was invited to complete the survey. The BHS is headlining that nearly one in five of respondents ‘knew personally of instances where horses had been suspected or confirmed as having been harmed by ragwort poisoning’ and is hoping that people will extrapolate that as applying to the general population of horse-owners.

That is not the case. You could argue that since just under 14,000 people completed the survey from a horse-owning population that the BHS itself says is 3.5 million then less that 0.5% of horse-owners have any interest in ragwort. Even if we say that only one in ten of the people who are concerned about ragwort bothered to fill in the survey that still means 95% of horse-owners who don’t think ragwort is an issue.

But what about that 1 in 5 anyway? These were people who ‘knew personally of horses that had health problems where ragwort poisoning was suspected or confirmed. This was among animals that either they owned or that were owned by their family, friends or neighbours’.

Jacobaea vulgaris (syn. Senecio jacobaea), common ragwort

‘Knew personally’ is not the same thing as saying ‘knew of incidents affecting ‘family, friends or neighbours’’. First of all, there is no attempt to define ‘friends’. Does that include people you know only from their posting in horsey forums? Even if it doesn’t it creates the possibility of the same incident being counted multiple times.

Suppose you belong to a riding club with 30 members, one of whom lost a horse ten years ago and maintains it was due to ragwort. If all 30 of you completed the survey, that one incident will have been counted 30 times. Go further, suppose that person has moved twice in those ten years, then three riding clubs have heard about the incident so, maybe, one incident was reported to the survey nearly 100 times.

Asking people to include ‘family, friends or neighbours’, therefore, makes the number of alleged incidents completely meaningless. I suppose something completely meaningless can’t be more completely meaningless but the example I created gives another reason for dismissing the survey. There is no time limit on the incidents. The survey did not ask for incidents that occurred in the past year or five years. It was open in terms of time. The BHS says that the average age of respondents was 30 and, given that horses tend to be a childhood interest that lasts a lifetime, for some, it seems to be reasonable to suggest that people were drawing on over ten years of experience when they reported that they ‘knew’ of incidents.

Jacobaea vulgaris (syn. Senecio jacobaea), common ragwort

There are plenty of other serious flaws in the survey but I’ll just deal with one. The BHS did not ask for any indication of whether the alleged incidents were the result of horses eating living plants or conserved forage containing ragwort. All the individual incidents involving cattle that I’ve seen were the result of conserved forage. Yet the BHS is trying to use its survey ‘results’ to promote a campaign of action against living plants growing in areas where they could not be a problem to animals of any sort rather than focussing on the people who take insufficient care when producing hay or other feedstuffs.

So, once again, the BHS has conducted a survey that has no value in determining the true extent of poisoning of horses. We have come nowhere since 2012 when I wrote:

‘Let me be completely clear about this; the surveys undertaken by the BHS will NEVER 'get a handle on the true prevalence of ragwort' and, even if they did, the prevalence is not important. It is the harm that matters and the BHS should spend its time discovering the true extent of disease from ragwort.’

 ‘My question to the BHS is, therefore, if it is convinced that common ragwort is causing such a problem, why does it not use some of its substantial reserves to undertake a proper, rigorous study of the effects of pyrrolizidine alkaloids (PAs) and then, if substantial effects are proved, finance a further study to identify the source of those PAs be it living Jacobaea vulgaris, conserved forage that has not been properly produced or any of the many other plants that contain PAs?’

'Poisonous Plants 1-2-1' introduction to common ragwort

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