What Causes Laminitis?

Spring is here and it’s the time of year owners with laminitis prone ponies dread! Laminitis is a painful and debilitating disease affecting 1 in 10 horses and ponies every year (Pollard et al., 2018).

Laminitis symptoms can start as a reluctance to turn or a stiff gait but can also present with a classic rocked back stance, shifting weight between feet, lying down more than normal, not wanting to move and obvious lameness. Horses will also have a bounding digital pulse.

How to take your horse’s digital pulse:

Feel either side of the fetlock with your fingers, run your fingers forwards and backwards until you feel a string like tube (this is the vein, artery and nerve bundle). Then press your fingers over this area and wait to feel a pulse. If you press too hard, you will cut off the blood supply and not feel a pulse, if you are too gentle you won’t feel the pulse either! It takes a bit of time to master this skill, so keep practicing! It is easier to feel in actively laminitic pony as their pulse will be bounding (or throbbing) and therefore much more obvious. Cobs and draft breeds with thick skin and feathers can be particularly difficult to feel! The more you practice, the easier it will be to find and notice any changes in the pulse quality and know what is ‘normal’ for your horse. If you are struggling to find the digital pulse, ask a knowledgeable friend or your Vet to help you locate it.

The approximate location for feeling the digital pulse.

X-ray of a horses foot, showing the normal position of the pedal bone. During laminitis, the pedal bone can rotate and/ or founder (sink) with devastating consequences.

X-ray of a horses foot, showing the relationship between the angle of the hoof wall and the pedal bone when rotation has occurred.

The good news is our understanding of laminitis has significantly increased in recent years thanks to research. Hopefully with a better understanding we will be able to prevent more cases.

90% of cases of laminitis have an underlying hormonal cause. Historically we thought too much grass was the problem, but we now know it isn’t that straight forward with laminitis affecting horses all year round, not just in Spring.

The 2 main causes of laminitis are Equine Cushing’s Disease (also known as Pars Pituitary Intermedia Dysfunction (PPID)) and EMS (Equine Metabolic Syndrome). Toxaemia (for example post colic or retained placenta post foaling), and load bearing/ mechanical laminitis (for example increased weight bearing on the opposite limb following fracture) can also cause laminitis.

Equine Cushings Disease is a disease of older horses and ponies, usually over 10 years old. Symptoms include:

• hairy curly coat (but in the early stages this may simply be noticed as slow to lose their winter coat).
• Laminitis
• Pot-bellied appearance
• Loss of topline
• Fat pads
• Lethargy
• Increased drinking and urination
• Recurrent infections
• Reduced Fertility

To diagnose Cushings Disease your Vet can perform a simple blood test. The most used screening test is a basal plasma ACTH test. Historically the ACTH blood test could only be taken at certain times of year as ACTH naturally increases in the Summer and Autumn due to the increased pituitary activity, but now following research laboratories use seasonally adjusted reference ranges to allow for this variation.

Equine Metabolic Syndrome describes a syndrome of obesity, laminitis and insulin dysregulation. As well as laminitis and obesity symptoms include abnormal fat deposits, difficulty losing weight, lethargy and infertility in brood mares. EMS has similarities with Type II diabetes in humans. EMS can be diagnosed by your Vet with a blood test, there are various protocols for testing for EMS, your Vet will decide which is the most appropriate for your horse, they usually involve looking at insulin levels.

EMS is mainly controlled by dietary management and a careful exercise programme under Veterinary guidance. Look out for part 2 of our laminitis series where we go into more detail about what actually happens in the horse’s body because of these hormonal syndromes.

If you have any concerns about your horse or pony, please contact your Vet for advice.

References:

Pollard, D., et al (2018) Incidence and clinical signs of owner-reported equine laminitis in a cohort of horses and ponies in Great Britain. Equine Veterinary Journal. 51(5), pp. 587-594