Paterson’s Curse (echium plantagineum) is a biennial herb sometimes called Salvation Jane. Native to the Mediterranean area, it was introduced into South Australia to provide feed for stock in times of drought.
While Paterson’s Curse may look colorful and attractive in the paddock, it is a deadly poison to the horse. It has since been declared a noxious weed and noxious it certainly is. Over the years there has been an increase of Paterson’s Curse poisoning of horses.
The herb is not normally palatable to horses and most will reject it if there is sufficient feed in the paddock.
Paterson’s Curse contains a substance called pyrrolizidine alkaloid that attacks and destroys the liver cells. Once destroyed, they are unable to regenerate.
There have been examples of horses being purchased in tip-top condition that have succumbed to Paterson’s Curse and died months later.
Horses usually are selective and intense feeders but in drought situations, they may be forced to eat Paterson’s Curse. As it is a broadleaf weed, it is more competitive with other foliage in the paddock.
If a horse ingests the toxin through hunger, it could well become addicted to the purple weed and prefer Paterson’s Curse to other grasses. Other animals, not so selective, might also eat the weed — so it is a “no-win” situation.
Removal from the infested pasture may not even help because the disease becomes progressive. The large build-up of scar tissue makes it impossible to repair and it is not only the paddock horses who succumb. Racehorses spelling, our prized hacks, and ponies are all at risk.
The symptoms of Paterson’s Curse poisoning can be most distressing for owners. By the time you realize the horse is ill, it is too late. With the decrease in the size of the liver, there is no chance of recovery.
With the increase of the toxins to the body, horses suffer brain cell damage, rendering them unable to experience pain. It is not unusual to find them caught up in wire with their legs cut to shreds.
Symptoms of Paterson’s Curse poisoning can be a loss of condition or weight. While this may be a symptom of other illnesses, if attributable to Paterson’s Curse, the horse will not recover.
Another is the horse’s preference for roughage, sticks, and twigs even though their usual diet is available. The blood count may range from the “anemic” to “normal” and show nothing wrong. Yet the horse may die some weeks later. A long type of coat frequently can be tell-tale sign.
This weed can cause a slow, debilitating degeneration of the horse but, if there is a rapid build-up of the toxin, the animal will surely die.
Diagnosis can often be difficult for veterinary surgeons and they recommend that horses grazing Paterson’s Curse-affected pasture’s be blood tested twice yearly to pick up early evidence of the problem.
Another noxious weed, Deadly Nightshade, contains the same alkaloid and if ingested may cause co-ordination problems and death.
It is the responsibility of all property owners to control this noxious weed. It is not a favorite in the horse’s diet and it will reject it if there are sufficient preferred feeds available.
Research by the CSIRO of the relationship between this alkaloid and the death of grazing animals, specifically horses, has proved Paterson’s Curse poisoning. Cropping control can be effective but for the hobby farmer or others with small lots, pulling by hand or the use of a weeding wand, may help eradicate the problem.
Unfortunately, for the horse, it is not that easy. By the time you realize there may be a problem, it is too late for the horse.
Government agistment paddock managers are very conscious of the problem. Paddocks are treated regularly and all horses agisted on them are removed for six weeks.
It cannot be stressed enough that once symptoms such as weight loss are evident, unfortunately for the horse it is all too late; it will not recover.