Hosts

  • Reservoir species: wildebeest, sheep, each transferring different forms of the virus
    • Innocuous to reservoir hosts
  • Dead end hosts: cows, kudu, some deer

Pathogenesis

Sever Oculo-nasal Discharge of MCF (Courtesy of Alun Williams (RVC))
  • Clinical signs in cattle:
    Fissures on tongue (no vesicles) in MCF (Courtesy of Alun Williams (RVC))
    • Necrotising lesions in upper respiratory tract and eye: conjunctivitis and corneal oedema / opacity (keratitis or "blue eye" - characteristic feature)
    • Fever and diarrhoea with severe oculo-nasal discharge
    • Not eating, dull with ulcers on muzzle may spread to rest of face with brown exudate
    • Ulcers also on tongue, dental pad, and cheeks that regularly become secondarily infected
    • Lymphocyte proliferation progresses in lymphoid tissue and blood until death
  • Lymph nodes completely replaced by lymphoblasts - similar to lymphosarcoma
  • Also vasculitis with medial necrosis of blood vessels throughout body with infiltration of walls of vessels by lymphocytes.
  • Ulcers are due to hypoxia of epithelium resulting from vascular lesions
  • Sporadically induce a fatal over-active T cell division, where virus encodes anti-apoptotic protein in dead-end host
  • Latent infection that is invariably fatal
  • Virus excretion increased during periparturient period

Epidemiology

  • Not all that common in UK
  • Affects whole body but especially evident clinically in face and mouth
  • Sporadic and often seen in animals mixing with sheep (carriers)
  • In parts of Africa see long outbreaks (diff serotypes) carried by Wildebeest
  • In deer produces very serious outbreaks, probably primarily sheep virus
  • Often youngish animal 6 months to 1 year

Control

  • Wildebeest should not be stocked in zoos where possible
  • Sheep and deer should be housed separately