ADVICEFROMTHE VET
In summary,liver disease in the horse often
presentsinitially with only verymild and vague signs. Blood testscan be used to demonstrate the presenceand severityofliver disease but rarely the cause.Ultrasonographyand biopsy mayprovide further information. In some cases, ‘outbreaks’ of liver disease canbeseen amongstgroups of horsesdue to ingestion of toxic substances or parasiteinfestation. If you have anyconcerns about changesinyour horse’s demeanor it is essential to have aveterinary examination carried out sooner rather than later so that problems canbedetectedearly,giving the best chanceofsuccessfultreatment.
ABOUT THE AUTHOR
horsesinthe UK is pyrrolizidine alkaloid toxicity cause by ingestion of ragwort. This toxin causes acharacteristic pattern of irreversible fibrosis (scarring) in the liver,usually recognisable on biopsy. Unfortunately,the damage often accumulates very slowly overaperiod of months to yearsand initial mild signs of disease may go unrecognised until alarge proportion of the liver is affected, at which point the horse may present with the sudden onset of signs of liver failure. If youthink it is possible that your horse mayhavebeen exposed to ragwort in hayor on their pasture, it would be worth considering having blood teststaken to establish early on whether liver damage is present, in order to institutesupportivetherapiesbeforeitistoo late. Similarly,ifone horse is diagnosed with ragwort-induced liver damage,itmakes sense to checkout field mates or other horsesthat have been fedonthe same hay. Although it is often said that ragwort is only palatable when dried in hay, this is by no means alwaysthe case,and ragwort plantsmustalwaysbedug up from any field in which horsesare grazed. Another cause of liver disease which can
potentially affectmultiple horsesinagroup is mycotoxin ingestion. Mycotoxins are harmful substances produced by moulds growing on crops during their production or storage.Wherean‘outbreak’ of liver disease is diagnosed in agroup of horses, the potential of mycotoxin contamination of feed canbe assessed by specialistforage screening. Liver fluke, although primarily aparasite
of sheep and cattle,isa potential cause of liver disease in horses, particularly those grazing wetareas wherethere aresnails on pasturethatisco-grazed with
sheep.Although flukeeggs cansometimesbedetectedin the droppings of affectedhorses, this is an unreliable means of diagnosis. Ablood test forantibodiestoliver flukeisnow available to use as ascreening tool in potential cases. Bile ducts within ahorse’sliver arechannels by which bile,usedinthe breakdownoffats, is
transported to the small
intestine.These can become blocked by an accumulation of debris and in extreme casesbile stones, or theycan be aroutevia which infection cantrack up from the intestine to the liver (cholangiohepatitis). Bile stonesand cholangiohepatitis may in some casesbediagnosed on hepatic ultrasound and liver biopsyrespectively. The liver is apotential sitefor development
of both primary and secondary neoplasia (tumours).Although not all of partsofthe horse’sliver maybevisualised by ultrasound, some tumoursmay be detectedinthis wayand biopsymay be used to confirm diagnosis. Hyperlipaemia is asyndrome in obese horses
and donkeyswherebyinthe face of systemic illness or astressor that leads to areduction in appetite, body fatisbrokendownand trigylcerides released intothe circulation. Excessivelipids are then takenupbythe liverwhere theyaccumulate and cause significant impairment of liver function. Successful treatment or management of liver
disease reliesonearly recognition of aproblem and wherepossible identification of the
cause.Insome cases, such as whereliver flukeisimplicated or bacterial infection is identified, specifictreatment is available. In other cases, such as hyperlipaemia, identification and treatment of concurrent underlying disease is
necessary.For other cases, removalofthe inciting cause and supportive therapymay enable adegree of recovery and improvement of clinical signs, depending upon the degree of irreversible hepatic fibrosis present. Dietary management of horseswith liver
disease is very important. Affectedhorses usually need small frequent feeds, containing easily digestible carbohydratesand adequate but not excessivelevelsofprotein. Antioxidant and vitamin supplementsmay be prescribed. Certain supplementssuch as those containing iron need to be avoided and drugs that require good hepatic function forclearanceshould only be used with extreme caution. Protection from sunlight to prevent photosensitisation causing skin damage is asensible precaution.
PleasementionCentralHorseNewswhenresponding toAdvertisementsAUGUST/SEPTEMBER2021 17
Naomi de Pennington MA VetMB CertEM(IntMed) MRCVS RCVSRecognised Advanced Practitioner in Equine Internal Medicine
Naomi, adirectorofthe Avonvale Equine Practice, is an RCVSRecognised Advanced Practitioner who leads the breeding and medicine services. She has particular interests in stud and foal medicine,gastroenterology and hepatology,ophthalmology and
cardiology.She frequently carriesout poor-performanceand weight loss investigations. She routinely performs gastroscopiesand is also an experienced colic surgeon. In her spare-time she is avery keen cyclist, as well as having a large menagerie of animals including 3 poniestolook after on her smallholding. •AvonvaleVeterinaryPracticeLtd. RatleyLodge,Ratley BanburyOX156DT
www.avonvaleequine.co.uk 01295670501
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