This infection may have an acute, chronic or sub-clinical (silent) phase.

• The acute phase characterised by intermittent fever associated with depression, lethargy, increased heart and breathing rates, haemorrhaging, diarrhoea with blood, bleeding wounds that won’t heal, lack of coordination and rapid weight loss. It can also cause petechial haemorrhages of the mucous membranes and general oedema more evident in the legs and jaundice.
• The chronic phase characterised by recurrent episodes of fever, anaemia and thrombocytopenia (decrease of blood platelets) interspersed with periods of normality. These episodes will be spread out over time.
• This disease is often fatal during the acute or chronic phase.
• Should the animal survive the acute and chronic phase, it enters a silent phase with no evident signs of illness for the remainder of its life. In this silent phase the virus persists but the clinical signs are only manifest if the immune system is weakened by another disease, stress or the administration of corticosteroids.