Equine Infectious Anemia

VIRUSES RETROVIRIDAE

Pathogenesis

• Virus coats red blood cells and thrombocytes
• Type III Immune complex disease develops
• Non-neutralizing antibody and complement lyse RBC's, causing:
  • Jaundice
  • Vasculitis
  • Hemorrhage
  • Diarrhoea
  • Loss of condition
  • Oedema
  • High mortality

Epidemiology

• Notifiable in UK but endemic in parts of the US
• Animals can be carriers for years despite being antibody-positive
• Transfer is mechanical via vectors:
  • Mosquitoes transfer infected macrophages
• Also transferred via infected needles, semen and milk
• Infected horses have lifetime latent infection of macrophages with recurring bouts of virus when immunocompromised

Diagnosis

• Coggins test required for horse movement in the US:
  • Serum antibody by immunodiffusion in infected horse spleen

Control

• Slaughter of infected animal
• 2 clear Coggins tests of all horses before movement allowed
• Vector control: stabling, etc.