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Comparison of ileal and rectal biopsies in the diagnosis of equine grass sickness
  1. T. S. Mair, BVSc, PhD, DEIM, DESTS, DipECEIM, MRCVS1,
  2. A. M. Kelley, BVetMed, MRCVS1 and
  3. G. R. Pearson, BVMS, PhD, FRCPath, FRCVS2
  1. Bell Equine Veterinary Clinic, Mereworth, Maidstone, Kent ME18 5GS
  2. School of Clinical Veterinary Science, University of Bristol, Langford, North Somerset BS40 5DU
  1. E-mail for correspondence tim.mair{at}
  • Ms Kelley's present address is Pet Doctors, 125/129 Chertsey Road, Woking, Surrey GU61 5BP

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EQUINE grass sickness (EGS) (equine dysautonomia) is a debilitating neurodegenerative disease of grazing equids (Doxey and others 1991, Wylie and Proudman 2009). It was first described in Scotland in the early 1900s (Spruell 1922), and although the precise cause is still uncertain, it is likely that it involves a neurotoxin (Gilmour 1973). Recently, a possible role of exotoxins produced by Clostridium botulinum type C has been implicated in EGS (Hunter and Poxton 2001, McCarthy and others 2004, Wylie and Proudman 2009). The disease has a high mortality, up to 95 per cent (Milne and others 1996), and is associated with degenerative neuronal changes involving the autonomic, enteric, central and peripheral nervous systems (Barlow 1969, Gilmour 1973, Scholes and others 1993a, Whitwell 1997, Cottrell and others 1999, Hahn and others 2001). The clinical signs of EGS include colic, dysphagia, sweating and muscle tremors, and the clinical disease can be classified as acute (duration less than two days), subacute (duration two to seven days) or chronic (duration more than seven days). Currently, EGS can be diagnosed conclusively in live animals only by histological examination of ileal biopsies obtained at exploratory laparotomy. Ileal biopsy is recommended because characteristic pathological changes are seen most consistently at this site of the gastrointestinal tract (Scholes and others 1993b, Doxey and others 1995, Whitwell 1997), and recently, both the sensitivity and specificity of formalin-fixed ileal biopsies were shown to be 100 per cent for the diagnosis of EGS (Milne and others 2010). The typical changes include severe neuropathy of the submucosal and myenteric plexi (Scholes and others 1993b, Whitwell 1997). However, the invasive and time-consuming nature of collecting and processing ileal biopsies …

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