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Japanese encephalitis in a racing thoroughbred gelding in Hong Kong
  1. K. H. K. Lam, BSc, BVetMed, CertVA, MRCVS1,
  2. T. M. Ellis, BVSc, MSc, PhD, MASM, MACVSc3,
  3. D. T. Williams, BSc, PhD4,
  4. R. A. Lunt, BSc5,
  5. P. W. Daniels5,
  6. K. L. Watkins, BVSc, MRCVS2 and
  7. C. M. Riggs, BVSc, PhD, DEO, DipECVS, MRCVS1
  1. 1Department of Veterinary Clinical Services
  2. 2Department of Veterinary Regulation and International Liaison, Hong Kong Jockey Club, Sha Tin Racecourse, Sha Tin, New Territories, Hong Kong
  3. 3Agriculture, Fisheries and Conservation Department, Veterinary Laboratory Division, Tai Lung Experimental Station, Lin Tong Mei, Sheung Shui, New Territories, Hong Kong
  4. 4Division of Virology, University of Glasgow, Church Street, Glasgow G11 5JR
  5. 5Commonwealth Scientific and Industrial Research Organisation (CSIRO), Livestock Industries, Australian Animal Health Laboratory, Private Bag 24, Geelong, Australia


A horse in Hong Kong that had been vaccinated against Japanese encephalitis suffered a pyrexic episode that culminated in a hyperexcitable state and self-inflicted trauma. Japanese encephalitis was diagnosed on the basis of clinical, pathological and serological observations, and confirmed by the detection of genomic sequences of the virus in spinal cord tissue. Phylogenetic analyses of E gene and NS5-3’UTR sequences revealed divergent clustering of these segments with previously described genotypes, suggesting the possibility that the horse might have been infected with a recombinant between genotype I and genotype II viruses. Horses are considered to be dead-end hosts for the disease, but the occurrence of an infected horse in a population may have implications for the health status of the national herd. The effect that this case had on the horse industry in Hong Kong is discussed with specific reference to the movement of horses and the vaccination programme for Japanese encephalitis.

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