24 ABSOLUTE HORSE NOVEMBER 2014 ABSOLUTE HORSE NOVEMBER 2014 25
What is epidemiology?Epidemiology is a branch ofveterinary science that studies thehealth status of populations, ratherthan individual animals.Epidemiologists are interested ininvestigating whether there areidentifiable patterns of diseaseswithin animal populations bylooking at the type of animalsaffected, their location, and howdiseases change over time. At the International Conference onEquine Laminitis and Diseases ofthe Foot in 2009, a panel ofveterinarians, farriers and researchersidentified epidemiology as the nextkey step in conquering equinelaminitis.
What is laminitis?Laminitis is one of the mostdevastating and debilitatingdiseases affecting horses and poniestoday. It is of particular significancebecause it poses a threat to allhorses and ponies – regardless ofhow well they are cared for.Laminitis is a complex disease thatoccurs when the lamellae (alsoknown as laminae) inside the footundergo degenerative changes.
There are thought to be threetypes of disease process whichresult in laminitis:
1. Excessive mechanical overloador traumaThis type of laminitis may occurfollowing direct trauma to the hoof,extensive concussive work orprolonged weight-bearing followingunilateral lameness.
2. Systemic inflammatoryresponse syndrome (‘SIRS’)Similar to human organ failure, thistype of laminitis may occurfollowing carbohydrate overload(gorging on concentrate feedstuffs)and inflammatory diseases such as
colic, diarrhoea and retention ofthe placenta after foaling.
3. Endocrinopathic disordersLaminitis occurring with obesity,pituitary pars intermediadysfunction ‘PPID’ (morecommonly known as ‘EquineCushing’s disease’), insulindysregulation such as EquineMetabolic Syndrome ‘EMS’, andfollowing steroid use has beentermed “endocrinopathic laminitis”.
How common is laminitis?It is difficult to estimate accuratelyhow common laminitis is overall;estimates have ranged frombetween 1.5% to 34.0% of thepopulation investigated. Specificsubsets of laminitis may occur onlyrarely; a study just published byRossdales Equine Hospital andDiagnostic Centre found only 11cases of laminitis considered to bedue to excessive mechanicaloverload in the past nine years.The most recent epidemiologicalstudy in Great Britain was a WorldHorse Welfare (WHW) fundedproject conducted with the AnimalHealth Trust (AHT) and RoyalVeterinary College (RVC). Thisstudy found that active, clinicallyapparent laminitis occurred in
nearly 1 in 200 veterinary-registered horses/ponies, andaccounted for nearly 1 in 200 first-opinion equine veterinary visits. Whilst it is very important that acorrect diagnosis and classificationof disease is made by a suitablyqualified person before anytreatment is initiated, it is likelythat laminitis is not alwaysattended by a vet and is thereforemore common in the generalequine population than this studyfound.The National Equine Health survey,run by The Blue Cross, collecteddata from 11,002 horses across theUnited Kingdom in May 2014.Worryingly, owners reported that7.1% of horses and ponies hadlaminitis, compared with 4.4% theyear before, and more laminitiscases were recorded as firstepisodes (43.0%) than the yearbefore (23.0%). We need more epidemiologicalstudies to determine whetherlaminitis is affecting more horsesand ponies throughout thecountry, or whether there has beenan increased awareness of thedisease that could be responsiblefor owners noticing new casesmore efficiently.
Why do some horsesdevelop laminitis and othersdon’t?In order to decrease the frequencyof laminitis, it is important tounderstand the features that makesome horses more or less likely todevelop laminitis. Two studies inGreat Britain have gathered thistype of information recently, assummarised in Table 1 aboveright.The best way to prevent laminitisoccurring in the first instance is toprevent, where possible, theunderlying disease processes
previously mentioned. It isbecoming increasingly apparentthat endocrinopathic disorders maybe responsible for the majority oflaminitis cases and there is goodevidence that their control canreduce the risk of laminitis. If yoususpect your horse or pony has anendocrinopathic disease, pleaseseek veterinary advice. Laminitis tends to recur inpreviously affected animals;therefore if your horse or pony hashad a previous episode of laminitisyou should be aware of the needfor ongoing collaborative foot
VetwatchEpidemiology of Equine Laminitis:
By Claire Wylie MRCVS
This pony is showing clinical signs of acute laminitis, predominantly in the forefeet.Leaning back in this classical ‘laminitis stance’ is thought to relieve pain by reducing theamount of weight being distributed through the painful lamellae at the front of the hoofwall. Image courtesy of WHW.
Divergent growth rings (rings that are narrow at the toe, becoming wider as they reachthe heel) are a sign of chronic laminitis. Other chronic laminitic changes to the hoofinclude: altered foot shape; changes in the hoof angle; sole bruising; widening of thewhite line and a palpable depression of the coronary band.
This radiographic image shows a horse with chronic laminitis. The lamellae thatnormally act to attach the pedal bone (the triangular bone at the bottom of the skeletallimb) to the hoof capsule have undergone such extensive degenerative changes that thebone is no longer being held parallel to the hoof wall but has rotated and sunk towardsthe ground.
management with your vet andfarrier. While an apparentassociation betweenshoeing/trimming and laminitismay be a direct result of poorshoeing or trimming in certaincases, it also may be suggestive ofearly clinical signs of laminitis. Iftherefore your horse or pony doesappear to be lame or foot-soreafter shoeing or trimming, makesure you seek advice from your vetand/or farrier.
How does this informationhelp you manage yourhorse?Some of the previously identifiedfactors are classed as “non-modifiable”, meaning that theycannot be influenced directly – noamount of stretching will increasethe height of your Shetland pony!However such information helpsidentify groups of animals forwhich efforts to prevent equinelaminitis should be considered ofparticular importance.Especially important at this time ofyear, is the strong evidenceshowing that laminitis is not just a
disease of the springtime. Infact, laminitis may be even
more likely to occur in the otherseasons, particularly if owners failto implement appropriatepreventive strategies when theythink their horse or pony is ‘safe’.Several of the recently identifiedfactors do present possiblepreventive opportunities, as listedbelow:
• Make all feed changes gradually –including access to new grazing.Be aware that recent research hasfound that even if ponies areturned out for only a few hoursthey are able to consume almosthalf their daily dry matter intakeby gorging on the grass when it ismade available to them! Grazingmuzzles are an effective way ofrestricting grazing in a naturalenvironment.
• Try to prevent your animalgaining weight over a relativelyshort period of time. Regularmeasurement of your animal’sweight will ensure that they arereceiving adequate energy supply.Research has found that soakinghay for a prolonged period oftime, in the right
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ROSSDALES EQUINE HOSPITAL & DIAGNOSTIC CENTRECotton End Road, Exning, Newmarket, Suffolk CB8 7NN. www.rossdales.com
Vet Profile
Name: Claire WylieQualifications: BVM&S, MSc,PhD, MRCVSYear of Qualification: 2004Claire joined the team atRossdales Equine Hospital andDiagnostic Centre in October2013. She is the Resident inEquine Clinical Research, aposition fully funded by TheMargaret Giffen Trust. Claire graduated from theUniversity of Edinburgh in 2004and subsequently studied for anMSc in Equine Science from theUniversity of Wales, Aberystwyth.For the research part of thisdegree she returned to Edinburghto conduct an epidemiologicalstudy of equine grass sickness(EGS). Following this she joinedthe Animal Health Trust’s Centrefor Preventive Medicine, where shehelped to develop the firstnationwide surveillance schemefor EGS, as a precursor to thecurrent vaccine trial. In 2008Claire commenced her PhD on theepidemiology of equine laminitisin conjunction with the AHT andthe RVC, which was generouslyfunded by World Horse Welfare.Claire’s PhD investigated thefrequency of, and risk factors for,equine laminitis in Great Britain,with the help of collaboratingveterinary practices in England,Scotland and Wales and theowners of horses and ponies withand without the disease. Uponcompletion of her PhD Clairespent a year working at theUniversity Autonoma in Barcelona– on a European Food SafetyAuthority tender reviewing theliterature regarding effectivecontrol measures for a diseasespread between dogs, sand flies,and humans. Claire is part of theCare About Laminitis study team,a team of veterinaryepidemiologists and laminitisresearchers hoping to help in thequest to conquer laminitis.
why should you CARE about laminitis?
Epidemiological studies require co-operation.This map shows the location of 30 vet practices(red triangle), and over 1000 owners whocompleted a questionnaire for a horse or ponywith laminitis (blue dot), or without laminitis(green dot) helping with the AHT-RVC study.
Factors associated with laminitis
Season
Sex
Height
Box rest
Endocrine disease
Grazing
Previous laminitis
Shoeing/trimming
Supplementation of regularfeeding
Transportation
Weight gain
Worming
RVC study of rescue animals on East Anglian farm between1997-2000, and 2005-2008, using veterinary-diagnosed cases
Increasing sunshine corresponded with increased laminitisfrequency, with most cases in May
Increased risk in mares compared to geldings
No association with height identified
Not studied
Not studied
Not studied
Not studied
Not studied
Not studied
Not studied
Not studied
Not studied
WHW-funded AHT-RVC study between 2009 and 2011, usingveterinary-diagnosed cases with owner-reported questionnaires
Increased risk in the summer and winter, compared to spring
No association with sex identified
Increased risk in smaller animals
Increased risk with box rest in the previous week
Increased risk with endocrinopathic disease history (PPID or EMS)
Increased risk with new access to grass within the past four weekscompared to those with no access, or access for a longer duration
Increased risk with previous episodes of laminitis
Increased risk if owner considered animal lame or foot-sore aftershoeing or trimming
Reduced risk with feeding of supplements compared to those notfed supplements
Reduced risk if transported in the previous week
Increased risk with increased bodyweight in the past three months
Increased risk with an increasing time since last worming
Table 1: Evidence for factors that make laminitis more or less likely in Great Britain
Laminitis is not just a disease of the springtime! The most recentepidemiological study by the AHT-RVC found a peak of laminitis occurredin January 2010, when there was exceptionally poor weather reducingaccess to grass to almost zero in many parts of GB. Be vigilant for casesof laminitis occurring all year round!
26 ABSOLUTE HORSE NOVEMBER 2014
Why should you CARE about laminitis? The study of diseases in populations is greatly enhanced by co-operation from thepopulation you are trying to study! Currently horse owners have a chance to beactively involved with a ground-breaking epidemiological study in Great Britain.‘CARE about laminitis’ is a new project that is working with horse owners and vets togather further epidemiological information. Following a period of piloting at RossdalesEquine Hospital, vets at Rossdales Equine Practice, and other vets across the country,have been helping to validate owner-reported data since the start of the year.The recently launched dedicated study website aims to recruit a large number of horseand pony owners throughout England, Scotland and Wales.For this study to be a success it is extremely important that both animals that will andwill not develop laminitis participate in the project. Because any horse or pony candevelop laminitis in their lifetime it is important that you do care about laminitis, evenif your horse or pony has never had it. If you take part in this study, you will be asked to complete a baseline questionnaireproviding general information about your horse or pony as well as health and medicalhistory; and your current management practices. A monthly follow-up questionnairewill detail if any of the information originally submitted has changed. Researchers willthen analyse the information to produce evidence-based guidelines to help reduce thefrequency of laminitis in the future.To take part in Care About Laminitis visit www.careaboutlaminitis.org.uk orcontact the PhD student responsible for the project, Mrs Dee Pollard, at theAnimal Health Trust via [email protected] or 01638 751000 (Ext: 1506).
A large epidemiological study oflaminitis that you can take part inhas just been launched acrossEngland, Scotland and Wales. ThisWorld Horse Welfare (WHW) studyis being run by the AHT and RVC incollaboration with MurdochUniversity and Rossdales EquineHospital. You can register atwww.careaboutlaminitis.org.uk.
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amount of water, reduces the amounts ofavailable carbohydrates.• If you horse is ill or injured, follow your
vet’s advice to ensure an appropriate planeof exercise can be maintained whilst onbox rest.
There were also a couple of unexpected andinteresting findings in the most recentresearch that require further investigationbefore any recommendations can be made.Firstly, animals that had been recentlytransported were less likely to developlaminitis. We certainly don’t recommend
that a trailer ride round the block willprevent laminitis, further investigation willexplore whether this was a ‘false’ effect thatmay have been identifying fit, healthy,middle-aged animals – in human studiesthis is known as a ‘healthy worker effect’.Secondly, there was an increasing risk oflaminitis with an increasing time since theanimal was last wormed, which may reflectgut damage, or improved general healthmanagement. Further work to explore this finding iscurrently underway and is necessary beforeany recommendations on wormingmanagement can be made.
Rossdales Equine Hospital & Diagnostic Centre(Equine referrals - all horse admissions)
Cotton End Road, Exning, Newmarket, Suffolk CB8 7NN. 01638 577754 (Office hours); 01638 663150 (24 hours) [email protected]
Rossdales Equine Practice(Ambulatory Practice, Pharmacy and Accounts) Beaufort Cottage Stables, High Street, Newmarket, Suffolk CB8 8JS. 01638 663150 (24 hours)[email protected]
