08/10/2022
Pyrrolizidine Alkaloid Poisoning is also known as Ragwort Poisoning, as it is most commonly caused by the Ragwort plant. This w**d is highly toxic to horses and the subsequent poisoning results in liver failure that causes long-term damage. Ragwort is not the only w**d that causes it, the list includes Senecio (ragwort), Crotalaria (woolly groundsel), Heliotropium (monkey tail), Amsinckia (yellow tarw**d), Echium (blue thistle), Cynoglossum (hounds tongue), and Trichodesma (borage forget-me-not) families, but they all have in common that they like to grow in temperate climates, though some require tropical or subtropical conditions to thrive. Horses, alongside cattle and pigs, are very susceptible to their toxins, but thankfully most of these w**ds, especially ragwort, have a very bitter taste which puts most horses off of grazing them.
The poisonous pyrrolizidine alkaloids present in ragwort cannot be processed by the liver and so they accumulate and over time, this compromised the healthy liver cells. As the function of the liver cells become compromised their numbers reduce, subsequently reducing the live function. The danger comes from the fact that there is most likely to not be any physical signs to alert the horse owner that this is happening, until it is already at a very dangerous level and quite often untreatable. In fact, sadly Pyrrolizidine Alkaloid Poisoning is often not diagnosed until after sudden death from liver damage. If the owner is fortunate enough to notice a change in their horse, the symptoms would include loss of condition, loss of appetite, dullness, malaise, constipation or diarrhea but likely to contain bloodstained faeces. There may be a build-up of fluid in the abdomen and jaundice may be seen in the whites of the eyes. Weakness progresses and the last symptoms would likely be of lessens coordination and wandering. Immediate veterinary care must be sort and any further intake of the toxic w**ds stopped, but horses at this stage of liver failure due to accumulative poising rarely recover.