Introduction

Asfarviridae receives it's name from African Swine Fever virus, which is derived from any of this family of viruses. ASF is a serious exotic virus that should not be confused with Classical Swine Fever.

Morphology

Large, enveloped, icosahedral, cytoplasmic DNA virus

Virulence and Pathogenesis

Infects either upper respiratory tract or skin via ticks
Enters bloodstream in [[monocytes]]
Reaches viscera and bone marrow within days
Induces a clotting defect and hemolysis in red blood cells
Also affects lymphocytes:
- Infects Th cells and causes them not to produce B-stimulating cytokines
- Antigen-stimulated B-cells undergo apoptosis rather than producing antibody
General cell signal transduction is blocked, decreasing non-specific immunity

Acute Virus (Africa)

Clinical Signs:
- Nasal discharge, diarrhoea, reddening of the skin
Death within 7 days
PM: widespread internal hemorrhage

Subacute Virus (Europe)

PM: Petechial hemorrhages may be seen under kidney capsule
Mortality: 30-70%
Survivors may lose body condition, have skin ulcers and joint swelling

Epidemiology

Can persist on infected premises for months
Subacute recovered pigs become antibody-positive carriers
Transfer:
- Africa: vertical transfer between soft ticks
- Europe/Africa: direct contact with carrier pigs, aerosol, infected swill, etc.

Diagnosis

Mortalities with widespread hemorrhage, particularly in lymph nodes
Test to distinguish from Classical Swine Fever and Porcine Circoviruses
Immunofluorescence
PCR

Control

No vaccine is available

Prevention:

Boiling swill
Isolation of sick pigs, domestic pigs from wild pigs
Keep pigs on concrete, not soil (to lessen tick contact)