Risk factors for equine laminitis: A systematic review with quality appraisal of published evidence

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Abstract

Epidemiological studies into the risk factors for naturally-occurring equine laminitis are limited. There are a small number of such studies, although the results are inconsistent and remain disputed. The reasons for the conflicting results remain unclear. The aim of this review was to critically evaluate previous research in order to identify publications which provide the best evidence of risk factors for naturally-occurring equine laminitis. A systematic review of English language publications was conducted using MEDLINE (1950–2010), CAB Direct (1910–2010) and IVIS (1997–2010). Additional publications were included by searching bibliographies. Search terms included laminitis, equine, risk factors and epidemiology. Publications which compared a case population to a control population and made inferences about parameters as risk factors for naturally-occurring equine laminitis were included. Information was extracted using predefined data fields, including 18 study quality indicators.

In total, 17 publications were fully appraised. Six were considered to provide the most reliable information about risk factors for naturally-occurring laminitis. Information on signalment was well researched and there was good evidence for an association with chronic laminitis and increasing age. There remain inconsistent results for many other horse-level risk factors including gender, breed and bodyweight. Previous publications estimating risk factors for equine laminitis were of reasonable quality, although they were limited in the number and scope of the risk factors studied. High-quality, evidence-based studies are needed to identify further risk factors and to establish consensus over previously identified risk factors for different equine populations.

Introduction

Laminitis is a disease of the foot which results in pain, lameness and loss of athletic performance (Herthel and Hood, 1999, Hood, 1999). The disease poses a threat to all Equidae. Laminitis affects a significant proportion of the general equine population, as highlighted by a recent review of 69 frequency publications (Wylie et al., 2011). Laminitis is known to have a complex and multifactorial aetiology of vascular, inflammatory, metabolic, endocrinopathic and/or traumatic/mechanical origin (Hood, 1999, Pollitt, 2010, Pollitt and Visser, 2010). The disease process, irrespective of its origin, ultimately results in lamellar degradation of the suspensory apparatus of the distal phalanx (SADP), leading to clinical signs of overt foot pain (Collins et al., 2010a).

Although many factors are considered to affect the risk of laminitis (Heymering, 2010), epidemiological studies into risk factors for naturally-occurring laminitis are limited (Bailey et al., 2004), and the results are inconsistent and disputed in areas such as signalment (Dorn et al., 1975, Slater et al., 1995, Polzer and Slater, 1996, Alford et al., 2001, Parsons et al., 2007, Menzies-Gow et al., 2010) and seasonality (Dorn et al., 1975, Polzer and Slater, 1996, Menzies-Gow et al., 2010). The reasons for the conflicting results are unclear. Preventive and therapeutic strategies and interventions therefore remain empirical and based largely on anecdotal rather than evidence-based medicine.

Intrinsic risk factors (for example, breed, age and gender) and extrinsic risk factors (for example, nutrition, exercise and health status) may differentially influence risk. Whilst some risk factors can be directly controlled or avoided through changes in general management practices, others cannot. Nonetheless, comprehensive knowledge and understanding of the risk factors for laminitis are needed in order to formulate new hypotheses regarding causal factors and the disease processes that can be tested scientifically. Additionally, identification of modifiable risk factors should allow development of enhanced preventive measures and the provision of new management guidelines for owners that should decrease laminitis occurrence within the horse population.

Systematic reviews are generally accepted as the ‘gold standard’ method for appraising quality of evidence, and PRISMA1 (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) guidelines have been produced to improve the systematic review process (Moher et al., 2009). Interrogation and evaluation of previously reported evidence will aid in elucidating potential disease mechanisms, allow identification of modifiable risk factors and appropriate intervention measures to minimise the disease threat.

The aims of this study were (1) to identify previous research providing information on risk factors for naturally-occurring equine laminitis; (2) to ascertain its scientific robustness, and (3) to identify what aspects of equine laminitis risk factors require further epidemiological investigation.

Section snippets

Materials and methods

This article is written in compliance with the PRISMA statement (Liberati et al., 2009, Moher et al., 2009). The protocol is described within this paper alone and was not registered with PRISMA.

Quality assessment

The initial database search identified 413 potential laminitis risk publications (Fig. 1). After adjusting for duplicates, 388 remained. Of these, 14 publications were excluded after reviewing the title and abstract because they were not written in the English language, or were books. The full text of the remaining 374 publications was examined in detail. Only 12 publications met the inclusion criteria for the systematic review. The majority of discarded studies failed to contain any

Discussion

This was the first study to perform a systematic review of published evidence of risk factors for naturally-occurring equine laminitis.

Overall the quality of risk factor publications was reasonable, and higher than a similar quality assessment of publications reporting the frequency of the disease (Wylie et al., 2011). Most publications (>82% overall, and 100% of the top six) aimed to identify laminitis risk factors and this focussed approach may have improved scores. Publication bias may have

Conclusions

This article summarises previous published research regarding risk factors for laminitis. Many of the publications focussed on easily measurable factors, such as signalment or season. It is important to re-focus investigations on risk factors of greatest potential importance to help us reduce the impact of the disease in the future through modifications and their evaluation by intervention studies. It remains appropriate to continue to investigate non-modifiable factors whilst there is a lack

Conflict of interest statement

None of the authors of this paper has a financial or personal relationship with other people or organisations that could inappropriately influence or bias the content of the paper.

Acknowledgement

This study was generously funded by World Horse Welfare.

References (60)

  • C. King et al.

    Preventing laminitis in horses: Dietary strategies for horse owners

    Clinical Techniques in Equine Practice

    (2004)
  • A.C. Longland et al.

    Pasture nonstructural carbohydrates and equine laminitis

    Journal of Nutrition

    (2006)
  • S. Love

    Equine Cushing’s disease

    British Veterinary Journal

    (1993)
  • P.M. McCue

    Equine Cushing’s disease

    Veterinary Clinics of North America: Equine Practice

    (2002)
  • D. Moher et al.

    Preferred reporting items for systematic reviews and meta-analyses: The PRISMA statement

    Journal of Clinical Epidemiology

    (2009)
  • R.M. Moore

    Vision 20/20 – Conquer laminitis by 2020

    Journal of Equine Veterinary Science

    (2010)
  • C.C. Pollitt

    Preface. Metabolic and endocrinopathic laminitis

    Veterinary Clinics of North America: Equine Practice

    (2010)
  • C.C. Pollitt et al.

    Carbohydrate alimentary overload laminitis

    Veterinary Clinics of North America: Equine Practice

    (2010)
  • K. Treiber et al.

    Inflammatory and redox status of ponies with a history of pasture-associated laminitis

    Veterinary Immunology and Immunopathology

    (2009)
  • D.M. Walsh

    Correlation of plasma insulin concentration with laminitis score in a field study of equine Cushing’s disease and equine metabolic syndrome

    Journal of Equine Veterinary Science

    (2009)
  • C.E. Wylie et al.

    Frequency of equine laminitis: A systematic review with quality appraisal of published evidence

    The Veterinary Journal

    (2011)
  • S.R. Bailey et al.

    How can we predict increased risk of laminitis in individual ponies or horses? Today and in the future

  • S.R. Bailey et al.

    Hypertension and insulin resistance in a mixed-breed population of ponies predisposed to laminitis

    American Journal of Veterinary Research

    (2008)
  • G.M. Baxter et al.

    Complications of unilateral weight bearing

    Veterinary Clinics of North America: Equine Practice

    (2009)
  • R.A. Carter et al.

    Prediction of incipient pasture-associated laminitis from hyperinsulinaemia, hyperleptinaemia and generalised and localised obesity in a cohort of ponies

    Equine Veterinary Journal

    (2009)
  • J.R. Coffman et al.

    Insulin tolerance in laminitic ponies

    Canadian Journal of Comparative Medicine

    (1983)
  • N.D. Cohen et al.

    Prevalence and factors associated with development of laminitis in horses with duodenitis/proximal jejunitis: 33 cases (1985–1991)

    Journal of the American Veterinary Medical Association

    (1994)
  • M.T. Donaldson et al.

    Evaluation of suspected pituitary pars intermedia dysfunction in horses with laminitis

    Journal of the American Veterinary Medical Association

    (2004)
  • C.R. Dorn et al.

    Castration and other factors affecting the risk of equine laminitis

    Cornell Veterinarian

    (1975)
  • M. Egger et al.

    Bias in location and selection of studies

    British Medical Journal

    (1998)
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