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Laminitis in the 21st century Luke Wells-Smith

Life as a veterinarian or farrier in the 21st century involves the diagnosis, treatment and management of one of the most debilitating conditions to affect the horse throughout history: laminitis. This article provides a commentary on the scientific evidence and is aimed at helping equine clinicians in their understanding of laminitis and highlighting potential areas for future research. New research in the field of paleopathology (the study of ancient diseases) has found evidence of laminitis in prehistoric horses, millions of years before equine species were domesticated (Wallet 2013). A study of wild horses also identified pathology associated with laminitis (Hampson and others 2011) which was thought to be influenced by environmental factors (Hampson and others 2012). In domesticated horses, the frequency of laminitis has been reported to range from 3 to 17.1 per cent. However, a recent study in Great Britain found that active episodes of laminitis accounted for nearly one in 200 veterinary visits (Wylie and others 2013), and in a study summarised on p 72 of this issue of Veterinary Record, the prevalence of supporting limb laminitis in one particular referral practice in the UK was found to be 0.02 per cent (Wylie and others 2014). With a long history of laminitis in prehistoric, wild and domesticated equids, the question is why, as veterinarians and farriers, do

Luke Wells-Smith, BVSc, Equine Podiatry and Lameness Centre, 14 Aberdeen Street, Muswellbrook NSW 2333, Australia e-mail: [email protected]

we struggle with the management of this condition? Every year our understanding of the pathophysiology of laminitis improves. The use of lamellar microdialysis (Nourian and others 2010) has allowed us to sample lamellar extracellular fluid in an attempt to further understand the initiating cause of laminitic episodes and has also recently been used to measure lamellar energy metabolism (Medina-Torres and others 2014). The discovery that experimentally induced hyperinsulinaemia causes laminitis (de Laat and others 2012) has greatly improved the understanding and management of cases with underlying metabolic conditions. Despite these advances in the understanding of the pathophysiology, horses continue to be euthanased due to clinical deterioration of many laminitis cases. Typically, laminitis is classified as being sepsis-associated, endocrine-associated or associated with supporting limb laminitis. Individual cases of laminitis may not be as straightforward, as there can be crossover between the above categories. For example, why don’t all horses with colitis develop laminitis? Obviously there are many variables in such cases, however, perhaps a horse that develops laminitis has an underlying endocrine disease, predisposing the lamellar attachment to severe damage. Orsini (2012) described the ‘perfect storm’ scenario, where multiple risk factors culminate in a severe episode of laminitis. Awareness of this overlap helps to identify at-risk cases and begin to implement a preventive plan. Physical examination of the laminitic horse is important when developing a

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Research Image: Rachel O’Higgins

construction of the heart bar shoe diagnosis, but there is no and the technique of dorsal wall pathognomonic clinical sign resection. Equine Veterinary Journal for laminitis. Radiographic 21, 367-369 Hampson, B. A., de Laat, signs in the chronic stages M. A., Beausac, C., Rovel, of laminitis are obvious, T., & Pollitt, C. C. (2011) such as lamellar wedge Histopathological examination of formation and phalangeal chronic laminitis in Kaimanawa feral horses of New Zealand. rotation; however, in the New Zealand Veterinary Journal 60, acute phase radiographic 285-289 signs can be difficult to Hampson, B. A., de Laat, M. A., Mills, P. C., Walsh, interpret (Sherlock and Parks D. M. & Pollitt, C. C. (2012) 2013). The venogram has The feral horse foot. Part B: been promoted as a way of radiographic, gross visual and histopathological parameters of providing further insight foot health in 100 Australian feral into laminitic episodes, but horses. Australian Veterinary Journal perhaps its real value lies not 91, 23-30 only as a one-off diagnostic, Kullmann, A., Holcombe, S. J., H urcomb e , but as a way to map the S. D., R o e ssn e r , laminitic episode and the H. A., Hauptmann, J. G., Digital venogram of a hoof six weeks after a severe laminitic episode response to treatment over Geor, R. J. & Belknap, J. (2014) Prophylactic digital cryotime (Rucker 2010). therapy is associated with decreased incidence of lamiprevention of sepsis-associated laminitis The treatment of laminitis over the nitis in horses diagnosed with colitis. Equine Veterinary (Pollitt and Van Eps 2004a, b) has been past century has been controversial and has Journal 46, 554-559 one of the most important breakthroughs centred around the use of various orthotics Medina-Torres, C. E., Pollitt, C. C., Underwood, C., Castro-Olivera, in laminitis research. The clinical use of to support the foot. The use of the heart bar E. M., Collins, S. N., Allavena, R. E., cryotherapy in colitis cases has led to a shoe and dorsal hoof wall resection were Richardson, D. W. & van Eps, A. W. (2014) reduction in laminitis development in one promoted heavily in the 1980s (Eustace and Equine lamellar energy metabolism studied using tissue microdialysis. Veterinary Journal 201, 275-282 particular hospital (Kullmann and others Caldwell 1989), whereas the application Nourian, A. R., Mills, P. C. & Pollitt, C. C. 2014). The understanding that insulin of wedged heel cuffs for the prevention and (2010) Development of an intra-lamellar microdialysis and diet play a major role in endocrinetreatment of acute laminitis were in favour method for laminitis investigations in horses. Veterinary associated laminitis allows veterinarians Journal 183, 22-26 from the 1990s to the present day (Redden Orsini, J. A. (2012) Supporting limb laminitis: the four to further educate owners on nutrition 2004). Recently, the Soft-Ride Boot was important whys. Equine Veterinary Journal 44, 741-745 and to implement management strategies developed to support the palmar aspect Pagan, J. D., Lawrence, T. J. & Lawrence, L. A. that may reduce the incidence of such of the foot and ease breakover. Regardless (2007) Feeding protected sodium bicarbonate attenuates hindgut acidosis in horses fed a high-grain ration. AAEP cases. Virginiamycin (Rowe and others of what orthotic is used to treat laminitis, Proceedings 53, 530-533 1994) and protected sodium bicarbonate it is important to monitor the response Pollitt, C. C. & Van Eps, A. W. (2004a) Prolonged, (Pagan and others 2007) have been used to with regular clinical, radiographic and continuous distal limb cryotherapy in the horse. Equine manipulate the bacterial colonies in the large Veterinary Journal 36, 216-220 venographic assessment. The promotion Pollitt, C. C. & Van Eps, A. W. (2004b) Equine intestine and to prophylactically reduce the of sole depth under the tip of the pedal laminitis: cryotherapy reduces the severity of the acute development of feed-associated laminitis. bone can significantly improve the comfort lesion. Equine Veterinary Journal 36, 255-260 Although there is now a large body of level of the laminitic horse, but this can be Redden, R. F. (2004) Preventing laminitis in the contralateral limb of horses with nonweight-bearing lamescientific evidence surrounding laminitis, the difficult to achieve in many cases without ness. Clinical Techniques in Equine Practice 3, 57-63 treatment of this debilitating disease remains a clear understanding of the biomechanics Rowe, J. B., Lees, M. J. & Pethick, D. W. (1994) challenging. Controlled clinical studies of the foot. In the author’s experience, Prevention of acidosis and laminitis associated with grain feeding in horses. American Institute of Nutrition: are difficult to perform and present ethical unloading the sole and dorsal hoof wall, Journal of Nutrition 124, 2742s-2744s dilemmas. Added to this, the heterogeneity elevating the heels and shifting load to the Rucker, A. (2010) Equine venography and its clinical of clinical laminitis cases makes critical palmar aspect of the foot appears to result application in North America. Veterinary Clinics of North evaluation difficult. However, systematic America: Equine Practice 26, 167-177 in positive outcomes in chronic cases of Sherlock, C. & Parks, A. (2013) Radiographic and evaluation of the effects of orthotics and laminitis. This can be achieved with many radiological assessment of laminitis. Equine Veterinary therapeutic shoes on clinical cases of different therapeutic shoes depending upon Education 25, 524-535 laminitis would be of great benefit to equine the case, with application aided by the use of Terry, R. L., McDonnell, S. M., van Eps, A. W., Soma, L. R., Moate, P. J. & Driessen, clinicians and farriers. radiographs. B. (2010) Pharmacokinetics and pharmacodynamics The recently established Veterinary Research has also focused on different of Gabapentin in horses: a potentially useful analgesic Equine Podiatry Group plans to develop pharmaceuticals for analgesia and to agent for the treatment of laminitis. Journal of Equine equine podiatry into a veterinary specialty Veterinary Science 30, 100-101 potentially improve blood supply to Wallet, L. A. (2013) Laminitic paleopathology: evithrough the American Veterinary Medical the foot of the laminitic horse. The use dence from the fossil record of Equus. Journal of Equine Association. This will bring together equine of acetylsalicyclic acid and isoxsuprine Veterinary Science 33, 840 veterinarians and farriers from all over the hydrochloride have been promoted for their Wylie, C. E., Collins, S. N., Verheyen, K. L. P. & Newton, J. R. (2013) A cohort study of equine world to further our understanding of the antithrombotic and vasodilatory effects, laminitis in Great Britain 2009-2011: estimation of disfoot, the treatment of laminitis and promote respectively; however, they have not been ease frequency and description of clinical cases in 577 the veterinarian-farrier relationship. critically evaluated in naturally occurring cases. Equine Veterinary Journal 45, 681-687 Wylie, C. E., Newton, J. R., Bathe, A. P. & laminitis. Gabapentin has been reported Payne, R. J. (2014) Prevalence of supporting limb for the treatment of neuropathic pain in References laminitis in a UK equine practice and referral hospital laminitis, but there are concerns about the de Laat, M. A., Sillence, M. N., McGowan, setting between 2005 and 2013: implications for future C. M. & Pollitt, C. C. (2012) Continuous infuepidemiological studies. Veterinary Record doi: 10.1136/ low bioavailability of the oral formulation sion of glucose induces endogenous hyperinsulinaemia vr.102426 (Terry and others 2010). and lamellar histopathology in Standardbred horses. As with any disease process, the holy Veterinary Journal 191, 317-322 grail is prevention. Cryotherapy for the Eustace, R. A. & Caldwell, M. N. (1989) The doi: 10.1136/vr.h53

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Laminitis in the 21st century Luke Wells-Smith Veterinary Record 2015 176: 70-71

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