Exotic Diseases

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Species Infected

only affects horses

Clinical Signs

• incubation 1-6 days
• fever and anorexia
• serous to mucopurulent discharge
• conjunctivitis, palpebral oedema, petechiation
• oedema of limbs, lower abdomen
• cough and dyspnoea
• colic, diarrhoea, jaundice
• weakness and dehydration
• abortion 70% mares early in disease
• mortality generally low; disease becoming more mild

Lesions

• referable to vasculitis
• congestion, petechiation and oedema
• thin walled vessels
• mucous membranes
• epi-, endocardium
• pulmonary interlobular septae
• lymph nodes
• mesentery
• adrenal necrosis and haemorrhage

Aetiology

• Arterivirus (Togaviridae)

Pathogenesis

• virus can cause severe endothelial destruction
• capillaries become nonpatent due to swelling of endothelium, thrombi
• leads to increased vascular permeability, haemoconcentration hypotension
• death due to terminal shock

Epidemiology

• viraemia present in infected horses for up to 19 days
• virus excreted in nasal, oral secretions as well as urine and faeces
• transmission is via direct contact, ingestion and inhalation
• increasing evidence that sub or nonclinical infections are occurring
• aborted foetuses have high titres of virus

Differential Diagnoses

     1.  EHVI abortion
     2.  strangles
     3.  purpura haemorrhagica
     4.  equine infectious anaemia
     5.  leptospirosis
     6.  African horsesickness