This post looks at the term laminitis and the causes and clinical signs the next post will look at diagnosis,treatment and management and prevention
What is Laminitis?
Laminitis is inflammation of the laminae of the foot.
The Laminae is the soft tissue structure attaching the pedal (coffin) bone to the hoof wall.
During laminitis, the blood flow to the laminae is affected, leading to inflammation, swelling and severe pain in the hoof. This ischaemic event causes the cells to become damaged and the laminae to die unless immediate intervention is undertaken. The death of the laminae leads to the pedal bone becoming unstable and if things go untreated, it can separate from the hoof wall and rotate within the capsule. If the pedal bone rotates too far it may protrude from the sole of the foot. In severe cases, this can lead to horses having to be euthanised.
Laminitis cannot be cured but it can be managed so prevention is the key to your horse living a long and happy life.
Causes of Laminitis
Whilst the exact process that leads to laminitis is unclear, there is an understanding that laminitis can arise in three general situations (1):
1) Diseases associated with inflammation – during these, inflammatory processes within the body are thought to lead to lamellar inflammation and trigger a failure of the adhesion between cells leading to laminitis
e.g. certain types of colic, diarrhoea, retained placenta, severe pneumonia
2) Endocrine (hormone) disease – during these situations, it is thought to be the hormone Insulin which is of high importance
e.g. Equine Cushing’s disease (pituitary pars intermedia dysfunction; PPID), equine, metabolic syndrome, excessive pasture consumption
3) Mechanical overload (supporting limb laminitis; SLL) – during mechanical overload situations, it is thought that in the leg undergoing excessive and continuous weight-bearing, blood supply to the lamellar tissue becomes inadequate.
e.g. associated with a fracture or infected joint the other leg which is bearing all of the weight is at risk of laminitis
Over feeding (grass and concentrates) (especially already overweight ponies) is one of the most common causes. especially in spring and autumn when daylight hours are lower but rain levels mean that the the soluble carbohydrate content in grasses and clovers is increased and when ingested, this causes metabolic changes that result in altered blood flow to the laminae of the foot.
Clinical signs of Laminitis
- Lameness affecting most commonly at least two limbs (most commonly the forelimbs are affected and more severely but all 4 can be)
- The horse leans back onto its heels and is reluctant to move
- The lameness is worse when the horse walks on hard ground or turns
- Shifting weight between feet when resting
- Increased digital pulses in the fetlock area (strong, rapid)
- Laying down more to offload the hooves
- Difficulty picking up a foot (as loads the other hoof to much)
- Pain with use of hoof testers at the point of frog on the foot or the toe
- Warm hoof wall/ coronet
- Changes in behaviour/temperament
- Laminitic “rings” on the surface of affected hooves corresponding to previous episodes of laminitis
- The hoof wall takes on a dish/slipper shape with long toes
- A bulge in the sole of the hoof where the pedal bone has rotated
- Restricted forelimb movement with increased weight-bearing on the hindlimbs in a ‘table-top’ or ‘laminitic’ stance. (4)
Reference 1: https://www.rvc.ac.uk/equine-vet/information-and-advice/fact-files/laminitis#panel-causes
Reference 2: https://kb.rspca.org.au/knowledge-base/what-is-laminitis-and-how-can-it-be-prevented-or-treated/
Reference 3: https://www.bluecross.org.uk/pet-advice/laminitis-horses
Reference 4: https://www.bhs.org.uk/advice-and-information/horse-health-and-sickness/laminitis