Exotic Diseases

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Species Infected

affects horses, mules and donkeys

Clinical Signs

• range of signs dependent on virulence of virus
• incubation up to 7 days
• intermittent fever

      2 syndromes

• acute or pulmonary form
• laboured breathing, paroxysmal coughing
• frothy liquid from nostrils
• recumbency, death within a few hours

• subacute or cardiac form
• oedema especially around head/temporal fossa, eyelids, lips, tongue, cheeks
• oedema of brisket, thorax, ventral abdomen may develop
• increasing abdominal respiration
• oral mucosa may become bluish

• recumbency, sweating, death
• mortality up to 90%

Lesions

• marked generalised oedema of subcutaneous and intermuscular tissue especially head
• acute pulmonary oedema
• hydrothorax, hydropericardium in some cases
• subendocardial and subpleural ecchymoses

Aetiology

• Orbivirus (Reoviridae)
• number of antigenic strains with only some cross-immunity
• vaccine effective but requires incorporation of a number of strains

Pathogenesis

• little known, but does appear to affect vascular endothelium

Epidemiology

• requires Culicoides spp. for mechanical transmission so presence of disease reflects the presence of vector
• disease can disappear during winter
• natural reservoir host is not the horse, and is unknown
• recovered horses can be symptomless carriers for up to 90 days
• endemic areas may have cyclic outbreaks at 10-20 year intervals

Differential Diagnoses

     1.  equine infectious anaemia
     2.  equine viral arteritis
     3.  purpura haemorrhagica
     4.  babesiosis