Laminitis is mostly associated with spring, and sudden flushes of lush grass, but recently I've heard of a few cases which have been triggered by other causes. Which led me to thinking that a blog post to educate my readers would be very useful.
The most common cause of laminitis in the U.K. is caused by obesity and overeating. Horse owners can be naive, and a lack of knowledge, peer pressure, pressure from feed companies, and unsuitably rich grazing can cause laminitis. Native ponies, who are the most common victims, evolved on sparse landscapes, so can actually live off far less than we realise.
Another cause of laminitis is toxaemia. This is when a systemic disease where the body is poisoned or infected (such as sepsis), such as pneumonia or post colic surgery, triggers laminitis. Unfortunately, in this case the laminitis won't improve until the disease is treated successfully.
Trauma, or mechanical, laminitis is caused by a physical external factor. That may be fast work on hard ground, or prolonged jumping on hard ground. Incorrect shoeing, or incorrect or prolonged poulticing can put pressure on the sole, which can lead to the laminae separating. Unfortunately I've have to mention to a couple of clients recently that I'm not happy with the way their horse is shoe because the hoof-pastern axis has been altered so I fear it is putting pressure on the tendons, ligaments, joints and tissue within the hood capsule.
If a horse has a non-weight bearing lameness they will shift their extra weight onto the opposite limb, so putting more pressure down the leg and risking laminitis. I knew a horse who had fractured his forearm, and was in a Robert Jones bandage for eight weeks in cross ties. There was talk at the time of the risk of stress laminitis in his good foreleg, but thankfully he was okay.
Iatrogenic laminitis is when corticosteroids are used to treat a horse, perhaps as injections for arthritis or tablets for viruses, and trigger laminitis as a side effect. If you've ever had your horse injected with steroids the vet should have told you very clearly that there is a risk of laminitis. This may mean that alternative medication is seeked, particularly if your horse is already prone to laminitis.
Most recently, experts have started linking laminitis to Cushings, or PPID. This sort of laminitis is linked to a hormone imbalance caused by a tumour on the pituitary gland. Many older horses develop PPID, which is why when a horse gets older you should become aware of the risk of laminitis and adjust your management routine and feed accordingly, because even horses who are just on the brink of having PPID could succumb to laminitis for no obvious reason. I recently heard of one older horse, who doesn't have any clinical signs of Cushings, developing laminitis as a result of being given steroid tablets for a cough. Now whether the laminitis was brought on by the steroids, although I'm pretty sure he'd have had steroids before in his life, or whether he was more susceptible because of his age and hormonal imbalance, you can only hazard a guess. Either way, it must be a very frustrating position to be in.
The final trigger of laminitis is stress. That is, overworking an unfit horse, undertaking long journeys in extreme weather conditions. I'm not quite sure how laminitis is triggered, but I guess that the stress causes too much ACTH to be produced which then upsets the hormonal balance, as with a Cushings horse, and then it is that which causes the laminae to become inflamed and to separate.
The experts still aren't sure how laminitis really occurs, but I'm sure new research and scientific advancements means that we'll get the answers soon and so be able to successfully prevent laminitis across the whole population.