The latest research on this common condition of the foot which can affect all horses.
What is laminitis?
Laminitis is a serious, debilitating but common condition of the foot which can affect all types and ages of horses. Laminitis can significantly compromise the welfare of the horse by causing immobility and excruciating pain which may lead to euthanasia1. In 2016 it was reported that laminitis accounted for 20.7% of all lameness cases with 42% of these cases being first episodes and 58% of them being repeat episodes2.
Laminitis is a condition affecting the sensitive lamellae structures which are located inside the horse’s hoof. The lamellae act as Velcro to form a strong bond to hold the pedal bone in place within the hoof. Laminitis causes weakening of these sensitive structures leading to the detachment of the lamellae from the pedal bone which can cause various degrees of pedal bone displacement and rotation in chronic cases3. A study4 found that laminitis can affect both the front and back feet, but it is more common and found to be the most severe when in the front feet.
1. Laminitis caused by an underlying hormonal (endocrine) condition
You keep two ponies together in a field and one develops laminitis and the other doesn’t- why is one susceptible to laminitis and the other isn’t? Traditionally it was thought that laminitis was caused by horses having access to lush pasture but this doesn’t explain why some horses develop the condition and others do not. Although grass intake can be a triggering factor it is now understood that 90% of laminitis cases are caused by an underlying hormonal condition.5
Figure 1: The classic laminitic stance. Photo courtesy of The Royal Veterinary College.
Hyperinsulinaemia (too much insulin in the body caused by insulin resistance) is the common direct trigger to the development of laminitis and is usually in association with the horse having one or both of two common hormonal conditions20 ; Equine Metabolic Syndrome (EMS) and Pituitary Pars Intermedia Dysfunction (PPID) commonly known as Cushings Disease.
As mentioned above, pasture can be a triggering factor but a hormonal disease is normally the primary factor behind the development of laminitis. Horses with EMS and/or PPID struggle to control their carbohydrate metabolism and therefore hyperinsulinaemia can occur easily in response to eating starches in grain or sugar in grass and hay which in turn increases the risk of laminitis. It is therefore suggested to think of laminitis as a clinical sign of a condition rather than an independent disease itself 6,7.
Recently a study8 was conducted looking into the risk factors to the development of laminitis. They found that cold blooded horse types who had access to high-quality grazing or had a change of pasture were at a significant risk of developing laminitis. Cold blooded horses, such as our native pony types are traditionally good doers to enable them to keep hold of their fat during the summer months to help them survive the cold and harsh winter months9. Native ponies also tend to be insulin resistant which increases the risk of the development of laminitis.
Pasture can be very high in sugar which as mentioned before can cause hyperinsulinaemia and consequently the development of laminitis.
2. Laminitis caused by inflammatory disease
It has been found that horses diagnosed with toxaemia (‘blood poisoning’) as a result of developing pneumonia, colitis (diarrhoea), grain overload or retained placenta (afterbirth) are at an increased risk of developing laminitis10.
An on-going concern that laminitis could be caused by corticosteroid administration (such as drugs to treat Recurrent Airway Obstruction (RAO) and musculoskeletal conditions) has recently been investigated. A study11 was conducted that concluded that there is no evidence to support that administration of therapeutic systemic corticosteroids can cause the development of laminitis in healthy horses. Another study12 also found that treatment with oral prednisolone (a type of glucocorticoid usually used to treat RAO) did not increase the risk of laminitis in healthy horses.
3. Laminitis caused by mechanical concussive overloading
Although rare, laminitis can be caused by excessive concussion of the feet, such as excessive roadwork, or by the overloading of one limb. An example of this was with the famous American racehorse Barbaro. Barbaro was the 2006 winner of the Kentucky Derby who sadly fractured his right hind leg in three places two weeks later. Barbaro’s fractured leg healed but he developed laminitis in his supporting left hind leg with resulted in him having to be euthanised13 .
There are two general stages of laminitis; acute (sudden onset) and chronic (long term) and you may not see all of these signs. Some signs are very subtle and can be mistaken for other lameness issues:
• ‘Footy’ horse being careful on hard or stony ground and/or preferring to walk on soft ground
• Shifting weight from foot to foot
• Classic laminitic stance- a horse rocking their weight onto their back feet (refer to figure 1)
• Reluctance to pick up feet
• Reluctance to walk
• Strong digital pulse
• Pain in the sole of the foot
• Bruising of the sole of the foot
• Hot feet (not always hot, can also be cold)
• Signs of pain and discomfort e.g. raised temperature, respiratory rate and heart rate
• Change in behaviour/temperament
• Lying down more than usual
• Signs of abnormal hoof growth and/or deep hoof rings in the hoof wall
• Change in the angle of the hoof wall
• Stretched white line.
Diagnosis and treatment
If laminitis is suspected a vet should be called to assess the horse immediately. If the horse is able to walk move them to a stable with deep bedding, ideally shavings; if not keep them where they are and wait for the vet to arrive. Remember that laminitis can sometimes be mistaken for other lameness issues and subtle signs can be easily missed. The vet will assess the horse and may decide to x-ray the hooves to ascertain pedal bone rotation/movement14 (refer to figure 2.)
The vet is likely to prescribe medication such as acepromazine (ACP) and/or phenylbutazone (bute). Vets will often work with the horse’s farrier to discuss the treatment options as in some cases frog supports may need to be fitted.
Pain management is extremely important for the welfare of the horse and the Horse Grimace Scale (HGS) is a recent concept that uses facial expressions of the horse to grade pain.15 A recent study16 found that the use of HGS was both successful and effective in the assessment of pain in horses with acute laminitis. HGS could then potentially be a valid and reliable tool for effective pain management of horses who have developed acute laminitis.
Besides the use of frog supports, anti-inflammatory medication and remedial shoeing/trimming for chronic laminitics there have been a number of studies looking into alternative treatments. A recent study17 concluded that the use of stem cell therapy had a significantly positive effect on the prognosis of horses with laminitis. They found that the use of stem cell therapy improved the distance between the pedal bone and the hoof wall in the majority of cases during the study. In addition, another study18 looked at the effects of placing a laminitic foot in a rubber boot containing 50% ice and 50% water (continuous digital hypothermia). They found that injury to the lamellae was significantly reduced when horses with acute laminitis were treated with continuous digital hypothermia.
Figure 2: An x-ray showing pedal bone rotation and separation from the hoof wall. Photo courtesy of The Royal Veterinary College.
As with all conditions and diseases prevention is always better than cure.
Laminitis caused by toxaemia can be prevented in a number of ways, for example making sure the feed room door is locked to avoid a lose horse gorging on the food and causing grain overload and also by closely monitoring a mare which is foaling in order to call the vet if a retained placenta is suspected. As mentioned above, although rare, laminitis can be caused by excessive work on the roads so it is therefore important to be careful when completing road work, especially if the horse is prone to laminitis, has an underlying endocrine disease or is obese.
On the other hand, there are steps to prevent laminitis caused by underlying endocrine conditions. As previously mentioned, over 90% of reported bouts of laminitis are caused by an underlying endocrine condition such as PPID or EMS and both can be diagnosed by a blood test. Although controllable through medication the development of PPID cannot be prevented. However, the development of EMS can be controlled by avoiding obesity. If your horse is predisposed to developing laminitis and/or prone to gaining weight such as a native pony or a ‘good doer’ then it is ever more important to control their weight to avoid obesity and therefore decrease the risk of laminitis.
• Use a correctly fitted grazing muzzle. The National Equine Welfare Council (NEWC) has produced guidance on the use of grazing muzzles
• Restrict grazing
• Feed hay which is nutritionally poor and/or soak hay for approximately 16 hours to reduce the content of fructans and sugars19
• Feed a mix of hay and oat/barley straw (50:50)
• Monitor the weight of your horse weekly by condition scoring and with the use of a weight tape
• Restrict or stop the use of grain feeds which are high in starch and feed low calorie, unmolassed feeds instead
• Daily exercise
• Dr Alex Dugdale has produced fantastic guidance on weight management
• Laminitis is a serious condition of the foot and can cause the pedal bone to rotate and lead to euthanasia in chronic cases.
• There are three general causes of laminitis: hormonal, inflammatory and concussive overload.
• Hyperinsulinaemia (too much insulin in the body caused by insulin resistance) is the common direct trigger to the development of laminitis
• Native ponies and ‘good doers’ are prone to obesity and naturally maintain higher insulin levels so are therefore at a higher risk of developing laminitis. Although, not all insulin resistant horses are obese (such as a horse with PPID).
• 90% of laminitis cases are caused by an underlying hormonal condition such as PPID and/or EMS (a horse can have EMS and PPID at the same time!)
• Call your vet for advice if your horse is showing signs of PPID or EMS. These two conditions can be diagnosed by a vet looking at the clinical signs and completing a blood test.
Other sources of information:
1) Welsh, C.E., Duz, M., Parkin, T.D. and Marshall, J.F., 2017. Disease and pharmacologic risk factors for first and subsequent episodes of equine laminitis: A cohort study of free-text electronic medical records. Preventive Veterinary Medicine, 136, pp.11-18.
2) Blue Cross. National Equine Health Survey. (2016). Edited buy Professor Josh Slater https://www.bluecross.org.uk/sites/default/files/downloads/NEHS%20results%202016%2022%20Sept%202016.pdf accessed 30/3/17
3) Morrison, S., Dryden, V.C., Bras, R. and Morrell, S., 2014. How to use stem cells in clinical laminitis cases. In Proceedings of the 60th Annual Convention of the American Association of Equine Practitioners, Salt Lake City, Utah, USA, December 6-10 2014 (pp. 499-503). American Association of Equine Practitioners (AAEP).
4) Wylie, C.E., Collins, S.N., Verheyen, K.L.P. and Newton, J.R., 2013. A cohort study of equine laminitis in Great Britain 2009–2011: Estimation of disease frequency and description of clinical signs in 577 cases. Equine veterinary journal, 45(6), pp.681-687.
5) Karikoski, N.P., Horn, I., McGowan, T.W. and McGowan, C.M., 2011. The prevalence of endocrinopathic laminitis among horses presented for laminitis at a first-opinion/referral equine hospital. Domestic animal endocrinology, 41(3), pp.111-117.
6) Karikoski, N., 2016. The Prevalence and Histopathology of Endocrinopathic Laminitis in Horses.
7) Bailey, S.R., Habershon-Butcher, J.L., Ransom, K.J., Elliott, J. and Menzies-Gow, N.J., 2008. Hypertension and insulin resistance in a mixed-breed population of ponies predisposed to laminitis. American journal of veterinary research, 69(1), pp.122-129.
8) Luthersson, N., Mannfalk, M., Parkin, T.D.H. and Harris, P., 2016. Laminitis: Risk factors and outcome in a group of Danish horses. Journal of Equine Veterinary Science.
9) de Laat, M.A., McGowan, C.M., Sillence, M.N. and Pollitt, C.C., 2010. Equine laminitis: induced by 48 h hyperinsulinaemia in Standardbred horses. Equine veterinary journal, 42(2), pp.129-135.
10) Pollitt, C.C., 2004. Equine laminitis. Clinical Techniques in equine practice, 3(1), pp.34-44.
11) McGowan, C., Cooper, D. and Ireland, J., 2016. No evidence that therapeutic systemic corticosteroid administration is associated with laminitis in adult horses without underlying endocrine or severe systemic disease. Veterinary Evidence, 1(1).
12) Jordan, V.J., Ireland, J.L. and Rendle, D.I., 2016. Does oral prednisolone treatment increase the incidence of acute laminitis?. Equine veterinary journal.
13) Luciani, G., 2007. Barbaro: A Champion Lives On. Bellwether Magazine, 1(66), p.25.
14) Spagnol, L.S. and Souza, V.R., 2015. Use of ozone therapy in chronic laminitis in a horse. Journal of Ozone Therapy, 1(1).
15) Dalla Costa, E., Minero, M., Lebelt, D., Stucke, D., Canali, E. and Leach, M.C., 2014. Development of the Horse Grimace Scale (HGS) as a pain assessment tool in horses undergoing routine castration. PLoS one, 9(3), p.e92281.
16) Dalla Costa, E., Stucke, D., Dai, F., Minero, M., Leach, M.C. and Lebelt, D., 2016. Using the Horse Grimace Scale (HGS) to Assess Pain Associated with Acute Laminitis in Horses (Equus caballus). Animals, 6(8), p.47.
17) Morrison, S., Dryden, V.C., Bras, R. and Morrell, S., 2014. How to use stem cells in clinical laminitis cases. In Proceedings of the 60th Annual Convention of the American Association of Equine Practitioners, Salt Lake City, Utah, USA, December 6-10 2014 (pp. 499-503). American Association of Equine Practitioners (AAEP).
18) Eps, A.W., Pollitt, C.C., Underwood, C., Medina‐Torres, C.E., Goodwin, W.A. and Belknap, J.K., 2014. Continuous digital hypothermia initiated after the onset of lameness prevents lamellar failure in the oligofructose laminitis model. Equine veterinary journal, 46(5), pp.625-630.
19) Longland, A.C., Barfoot, C. and Harris, P.A., 2011. Effects of soaking on the water-soluble carbohydrate and crude protein content of hay. Veterinary Record-English Edition, 168(23), p.618.
20) De Laat, M.A., Clement, C.K., McGowan, C.M., Sillence, M.N., Pollitt, C.C. and Lacombe, V.A., 2014. Toll-like receptor and pro-inflammatory cytokine expression during prolonged hyperinsulinaemia in horses: implications for laminitis. Veterinary immunology and immunopathology, 157(1), pp.78-86.
a. Similar to type II diabetes in humans EMS describes a collection of clinical signs including obesity, regional adiposity, insulin resistance and existing or previous laminitis. More information can be found by reading Johnson, P.J., Wiedmeyer, C.E., LaCarrubba, A., Ganjam, V.S. and Messer, N.T., 2010. Laminitis and the equine metabolic syndrome. Veterinary Clinics of North America: Equine Practice, 26(2), pp.239-255.
b.PPID is a complex hormonal disease based on the increased production of the hormone cortisol which is common in horses over 15 years old. More information can be found by reading Schott, H., 2015. Recommendations for the diagnosis and treatment of pituitary pars intermedia dysfunction (PPID). Equine Endocrinology Group.