Papular proliferative pathology

Ring Zone Lesions of BPS - Calf (Courtesy of Alun Williams (RVC))
  • Parapox virus
  • Very similar disease to orf but seen in cattle and generally milder condition.
  • Must be differentiated from Foot and Mouth Disease and Mucosal Disease.
  • Sporadic, in cattle, less than 1 year old.
  • Develop papules on the muzzle, external nares and in the oral cavity; the oesophagus and forestomachs may also be affected.
  • Usually heals spontaneously.
Pathogenesis
  • The early lesions are round areas of intense congestion up to 1.5 cm in diameter.
  • The centre becomes necrotic and slightly depressed.
  • Slow peripheral extension of this lesion gives a classical ring zone formation with concentric rings of
    • yellow (necrosis),
    • grey (epithelial hyperplasia)
    • red (congestion).
Histology
  • There are focal areas of hydropic degeneration in the stratum spinosum
  • Large eosinophilic intracytoplasmic inclusion
  • Epidermis is markedly thickened.
  • The superficial layers of the epithelium become necrotic and slough.
  • Vesicle formation is not a feature of this disease.