Asfaviral Flashcards
General Characteristic of Asfaviral
- linear dsDNA virus which is icosahedral in shape and has an envelope
- Has 1 serotype and has variant virulence
- Arbovirus!
- No virus neutralisation possible! Haemadsorption is possible,
- Highly resistant! Can survive in the environment for 100-200 days and in the freezer for years. Sensitive to disinfectants (2% NaOH, 0.3% formalin, hypochlorite, iodine)
African swine Fever
Species affected
*It is a soft tick virus that affects:
• Swine and Wild Boars
• African pig species
African swine Fever
Most susceptible
All age groups
African swine Fever
Occurrence
Endemic in Africa
First case in Hungary in 2018 in wild boars!
African swine Fever
Spread
- Soft tick virus that infects swine (Ornithodorus sp)
- Also by contact with infected pugs and their secretions
- Virus survives in meat!
African swine Fever
Pathogenesis
PO/Tick infection —> tonsils, lymph nodes —> viraemia
(extended for months) —> generalised infection:
• Spleen
• Lymph Nodes
• Bone Marrow
• Vascular Endothelium —>haemorrhages and oedema
*Viral replication in:
• Monocytes and macrophages
• Endothelial cells
• Hepatocytes
• Tubular epithelial cells
• Granulocytes
• No replication in lymphocytes!
*No virus neutralisation —> cytoplasmic membrane of the macrophage is taken
*Immune complex formation —> Type III Hypersensitivity
reaction!
*Virus is shed with the saliva and nasal discharge (will be present in secretions 48h before clinical signs!)
African swine Fever
Primary replication
*Tonsils, lymph nodes
Incubation time:
• 2-3 days for highly virulent strains
• 1 week for moderately and low virulent strains
African swine Fever
Target organs
*All tissues will have a high concentration of the virus
African swine Fever
Clinical signs
*General clinical signs: • General and febrile signs (40-41℃ fever) • Transient anorexia • Abortion (all virulence strains) • Haemorrhages —> skin, snout, lymph nodes *Outcome depends on strain virulence: • (1)Highly virulent strain —> Peracute • Animal shows clinical signs at 1-4 days • Sudden death (at days 7-10) with no neurological signs • Depression • Skin lesions • Mortality: 90-100% • (2)Moderately virulent strain —> Acute • Animal shows clinical signs at 7-20 days • Prolonged fever • Depression • Anorexia • Skin lesions • Abortion • Mortality: below 60% • (3)Low virulent strain —> Chronic • Animal shows clinical signs at 15-21 days • Immune-complex formation • Multifocal skin necrosis • Swelling of carpal and tarsal joints • Abortion and seroconversion • Pneumonia • May be asymptomatic! • Mortality: below 10% In the wild boar there is milder clinical signs, usually in chronic form
African swine Fever
Pathology and histopathology
*Acute form: • Hyperaemia • Haemorrhages everywhere • Black lymph nodes • Pulmonary oedema • Enlarged spleen • Decreased leukocyte count *Chronic form: • Splenic and lymphoid hyperplasia • Fibrin rich fluid in pericardium, thorax and abdominal cavity • Pneumonia • Skin necrosis (because of immunocomplexes)
African swine Fever
Diagnosis
*History, clinical signs and PM lesions —> can’t be differentiated from CSF just by looking at them!
Detection of virus: PCR, IF, Haemadsorption
Virus isolation
Detection of antibodies: ELISA
Animal infection —> pigs immunised with CSFV versus non immunised animals
No VN!
*Notifiable Disease!
African swine Fever
Treatment
No effective treatment
African swine Fever
Prevention and immunity
*General epidemiological measures
• Strict disinfection
• Control of movement
• Treatment of waste food
Tick control
Ensure neither infected live pigs nor infected pig products are introduced in ASF free areas
*No vaccine available!
*Eradication programmes involving rapid diagnosis, slaughter and disposal of all animals on infected premises
*In disease free countries:
• Serological surveys of pigs with in control zones (ensure all infected pigs have been identified)
• Stamping out of the infected herds
• Disinfection
• Leave empty for 1 month before repopulation
• Movement restriction for 1 month after repopulation followed by serological control
