Equine Arteritis Virus

Antigenicity

• Most cases are subclinical and only antibody positive

Hosts

• More common in thoroughbreds

Pathogenesis

• Infects nasopharynx and spreads locally, causing:
  • Dypsnoea
  • Coughing
  • Diarrhoea
  • Colic
• Spread to lymphoid tissue leads to leukopenia and immunosuppression
• Typical medial necrosis of arteries causing:
  • Hemorrhage
  • Abortions occur after 10-30 days in 50% of pregnant mares (as opposed to Equine Herpes, which shows late abortions)
  • Oedema - particularly ocular, giving rise to "pink eye"
• Other clinical signs include:
  • Pyrexia
  • Nettle rashes
  • Ocular and nasal discharge
  • Swelling of legs or scrotum
  • Stiffness of gait
• Foal death caused by interstitial pneumonia
• Stallions become intermittent or persistent shedders from accessory sex glands but may show no clinical signs

Epidemiology

• Controlled virus in the UK but AI and breeding schemes presents a real risk

Diagnosis

• Clinical symptoms, but may be variable
• PCR on semen
• ELISA for serum antibody

Control

• Vaccines:
  • Stallions: Live attenuated
  • Mares: Killed whole virus
• Clinical disease is NOTIFIABLE
  • Seropositive stallions restricted from teasing, mating or AI unless PCR tested negative
  • Persistent shedders should be castrated
• Serology on imported horses
• Mares tested within 4 weeks of mating
• In an outbreak, isolate and restrict movement until antibody-negative for one month