Exotic Diseases

Return to Exotic Diseases Index

Click on the images on this page to see a larger image and more information

Species Infected

affects only pigs

Clinical Signs

• peracute disease
• sudden death may be first sign of an initial outbreak

• acute disease
• incubation 2-5 days
• fever, depression, inappetence
• incoordination and recumbency
• cyanotic blotching of skin of snout, ears, abdomen
• nasal, ocular discharge respiratory distress
• vomiting, diarrhoea
• abortions
• death up to 7 days
• mortality 100%

• chronic disease
• signs persist longer
• not as typical or as severe
• some may recover

Lesions

• resemble swine fever, but are more severe
• referable to severe blood vessel damage
• oedema, ascites, hydropericardium, hydrothorax
• haemorrhages on most serosal/mucosal surfaces as well as endo and epicardium
• pulmonary ecchymoses and oedema
• infarction and necrosis of many organs
• important lesions involve lymph nodes
• these are more severely affected than in swine fever
• marked haemorrhage in node resembles haematoma
• splenomegaly often localised, infarctions can occur
• button ulcers, renal and bladder haemorrhages not as marked as swine fever

Aetiology

• formerly classified in Iridoviridae - now the sole member of a separate DNA virus family
• infects Ornithodorus spp. ticks
• highly resistant to heat, dryness, putrefaction and chemical disinfectants
• can survive for 6 months in uncooked hams, 3 months in infected premises and 18 months in discharges

Pathogenesis

• pigs become infected by direct contact, indirect contact, aerosols or via insect vector
• primary route of infection is the upper respiratory tract; lower respiratory tract is also a route
• replication of virus occurs in pharyngeal tonsils and lymph nodes draining the upper respiratory tract
• viraemia is associated with red and white cells
• virus has affinity for reticuloendothelial system resulting in destruction of monocytes, lymphocytes and endothelium
• after the first 24 hr of fever, virus appears in secretions and excretions
• recovered pigs become chronic carriers

Epidemiology

• current international spread is causing more concern than any other livestock disease
• in Africa, virus reservoir in warthogs, bush pigs that show no clinical signs but are lifelong carriers
• these serve as virus source for ticks more than domestic species
• tick is involved epidemiologically
• virus can be passed from generation to generation without the need for pigs
• are lifelong carriers
• have implications for Australia as similar ticks are present here
• between country spread has been invariably due to infected garbage from ships and aircraft
• in an outbreak spread is by direct pig contact, or by contact with infected garbage, or indirect contact through facilities and personnel
• blood sucking insects including ticks could also have a role

Differential Diagnoses

     1.  swine fever
     2.  acute salmonellosis, erysipelas, pasteurellosis
     3.  thrombocytopaenia purpura
     4.  warfarin poisoning
     5.  pseudorabies