Hosts

  • Horses and Man
  • Reservoir host: birds, mosquitoes

Pathogenesis

  • Virus oscillates between definitive and reservoir populations
  • Aseptic encephalitis with concurrent fatalities

Epidemiology

  • Virus originated in Africa
  • Two versions seem to exist:
    • Old world avirulent strain
    • New world virulent mutant
  • Entrance to US via mosquitoes was followed by a rapid sweeping spread across the country with deaths of horses and birds
  • UK birds show antibody but no reported deaths

Diagnosis

  • Virus isolation
  • RT-PCR on CSF

Control

  • Vector control (mosquitoes): drain standing water, sprays, etc