Asfarviridae Flashcards
What is the general structure?
Enveloped
Complex icosahedral capsid
Linear double-stranded DNA
Replication mostly in cytoplasm (initial stage in nucleus)
How many genotypes have been identified?
22
Some strains have 100% mortality while some have no infection.
What is the common name?
African Swine Fever
Who are the hosts for ASF?
Domestic pigs & European Wild Boar
Who are the inapparent carriers?
Warthods, bush pigs, and giant forest hogs Sylvatic cycle (wild, jungle)
Is ASF reportable?
Yes! OIE List A Disease High morbidity and mortality Import and export bans Quarantine and depopulation Can become prolonged epidemic
Where is ASF endemic?
Most sub-Saharan Africa Island of Sardinia in Italy Georgia, Armenia Russia Poland Latvia
How long can the virus survive?
30 days in pens
They are resistant to a wide range 4-13 of pH
Can survive in chilled carcass for 6 months
Frozen carcass - 2 years
What is a distinguishing characteristic of ASF-virus?
It does not hemagglutinate!
RBC’s will adhere to the surface of pig monocyte or macrophage infected with ASF-vurus.
Hemadsorption (HAD) is attributed to a virus specific protein that appears on the plasma membrane of infected cells during late infection.
Who are the vectors for transmission?
Soft ticks including;
- Ornithodorus spp. (specifically O. moubata)
O. erraticus
How does tick to tick transmission occur?
Trans-stadial
Transovarial
Sexual
How does the sylvatic cycle occur?
Transmission between warthogs and soft ticks
Young warthogs infected develop a viremia with high enough virus titers to infect ticks feeding on them
How does the domestic cycle occur?
Bite from an infected tick Direct contact with infected animal (oronasal) Indirect contact on fomites Eat infected pork Aerosol spread Biting flies
What are the pathogenic effects of ASF virus?
Hemorrhage
Apoptosis
Leukopenia, lymphopenia, thrombocytopenia
Where does the virus replicate?
Pharyngeal mucosa, tonsils
Endothelial cells
Megakaryocytes
Macrophages
What protein of the virus induces apoptosis of the cells?
p54
What are the clinical signs of per-acute infection?
1-3 days of pyrexia, hyperpnea, hyperemia before death or sudden death
What are the clinical signs of acute infection?
High fever Moderate anorexia Erythema Cyanotic skin blotching on ears, tail, lower legs Respiratory Distress Diarrhea & Vomiting Abortion (sometimes first sign)
What are the clinical signs of the chronic form?
Emaciation & stunting
Swollen joins
Ulcers and reddened or raised necrotic skin foci
Pneumonia
How is ASF diagnosed?
Virus isolation from blood, spleen, LN, tonsils
Hemadsorption
Serology: FAT
PCR to detect viral DNA
How is ASF prevented?
Control hygiene
Movement of pigs outside the country should be controlled.
Do not feed swill that contains pig remnants
Is ASF reportable?
YES!
Immediately notify authorities since infected farms must be placed on quarantine.
How is ASF controlled once diagnosed?
Cull all infected and in-contact with animals
Carcasses must be burnt or buried deeply on site
Disinfect fomites
