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Diagnosis of the nervous form of maedi-visna infection with a high frequency in sheep in Castilla y León, Spain
  1. J. Benavides, DVM1,
  2. N. Gómez, DVM1,
  3. D. Gelmetti, DVM, PhD2,
  4. M. C. Ferreras, DVM, PhD1,
  5. C. García-Pariente, DVM1,
  6. M. Fuertes, DVM1,
  7. J. F. García-Marín, DVM, PhD1 and
  8. V. Pérez, DVM, PhD1
  1. 1Departamento de Patología Animal, Medicina Animal (Anatomía Patológica), Facultad de Veterinaria, Universidad de León, Campus de Vegazana s/n, 24071 León, Spain
  2. 2Istituto Zooprofilattico Sperimentale Lombardia- Emilia, Via Bianchi 7, 25124 Brescia, Italy
  1. Correspondence to Dr Pérez


Between 1997 and March 2004, the nervous form, or visna, of maedi-visna infection was diagnosed in 71 of 1631 sheep (4·35 per cent) examined in the Castilla y León region of Spain, of which 634 had shown nervous signs. The presence of the virus was confirmed by immunohistochemistry and in some cases by PCR on frozen-thawed or paraffin-embedded tissue samples. The main clinical signs were hindleg ataxia and paresis, but blindness or nystagmus were also observed. Thirty-three of the affected sheep (46·5 per cent) were two years old or younger. The affected sheep showed variable degrees of a non-suppurative meningoencephalitis, and immunohistochemistry identified positive cells in all cases, with no relation to the intensity of the inflammatory lesion.

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