Ragwort and horse deaths.

Ragwort dot org's home page

Ragwort and DHMO How fear of something is not always rational.

What is the real truth about horse deaths How statistics can be used to mislead.

How toxic is ragwort Not as much as you might think.

Why ragwort doesn't poison humans. A widespread myth debunked.

The law and ragwort Why there is no general obligation to control it.

Government bloopers Incorrect or misleading advice from councils and government.

Before we actually examine the claims of large numbers of deaths and why they are false. It is important to understand how ragwort poisons animals. The alkaloids in ragwort are not actually poisonous in themselves but after a series of steps produce chemicals which can damage the liver. These symptoms are not very specific. They are just the symptoms of liver failure. This can have many causes. Only with rarely held post mortems is it possible to diagnose ragwort poisoning. Even then care has to be excercised. The pyrrolizidine alkaloids in Ragwort occur in 3% of the world's plants(1) and eating them can also cause problems. Worse still the breakdown product pyrroles which actually cause the problem can be found in other sources - ypically from burning things. One suspected poisoning case in cattle was initially blamed on ragwort but an incinerator was eventually found to be at fault. (2)

One often reported claim was the result of a particularly badly carried out survey of vets which produced the enormous number of 6,500 horse deaths a year. It still regularly surfaces in newspaper articles and in press releases, by some quitre prestigious organisations but it is more than unreliable. It gives the impression that statistics have been used to mislead. A large number of vets were contacted and were asked for the number of cases that MIGHT BE ragwort poisoning that they had seen. A small number responded and this figure was then multiplied up as if everyone had responded. Of course this is bad statistics. It is very dangerous to use figures like this. It is obvious that if you had a case you were more likely to respond and you cannot get a reliable result by extrapolating like this, especially using cases that are unconfirmed in your figures. Even without the information that the figures were suspect, experts were doubting them.

This is what one vet wrote in a letter to the Sunday Telegraph.

Re: Cherchez les toxins Date: 3 August 2003

It seems that ragwort is fast becoming the subject of a nationwide outburst of hysteria similar to that caused by salmonella in eggs (News, July 27). In the hope of calming it, I offer the following thoughts

. Yes, ragwort is poisonous to horses, cattle and sometimes sheep. It can cause acute liver damage in young stock, but this is rare. It is most commonly encountered as chronic liver damage in older animals. But ragwort is distasteful to horses and cattle, and they will eat it only if they are half-starved on a pasture that is bare of almost anything else.

In the agricultural depression of the 1930s and during the Second World War, there was far more ragwort around than there is today. There were no selective weedkillers available, so it had to be controlled either by hand-pulling or by allowing sheep to graze off the young plants, which are less poisonous. There were also many more horses in the country, working on farms or pulling delivery vans. Ragwort poisoning was a recognised disease, but not a major problem.

Any good stockman would not leave his animals on a bare pasture with ragwort. I find it hard to believe that so many of today's horsemen and women leave their horses on bare ragwort-infested pasture that 6,500 of animals succumb to ragwort poisoning annually. I realise that some ragwort could be bought in with hay, but ragwort is easily spotted, is normally rejected by the horse and is in any case easily removed by the groom/ owner. It could be more of a problem to those few horses that are fed silage.

I suggest that if 6,500 horses are dying of "ragwort-like" liver damage each year, it is time to look for other possible toxins. Pesticides added to grain to control weevils and mites are certainly one possibility.

From: Frances Wolferstan BA, Vet MB, MRCVS, Tamworth, Staffordshire

So what is the truth? Well there are several mentions of the rarity of poisoning in the scientific literature. One french paper actually involved the deliberate poisoning of animals because they thought the French ragwort might be different because they had not heard of any cases.(3) In another study it was actually found that there were a few cases. Just six in a period of around a decade. Not many at all. After all the attention drawn a more cases turned up in Britain. A goverment report shows 13 in one year.(4) There might still be more cases but this puts the bad survey into context. In fact horses won't eat ragwort unless either they are forced to or it is in hay. Unfortunately the anti-ragwort campaign doesn't focus on the real problem and creates problems by claiming, falsely, that it is a danger ouside hayfields , that it is poisonous to the touch or can be breathed in.