Asfarviridae & Adenoviridae Flashcards
What does Asfarviridae stand for?
African Swine Fever And Related viruses
Describe Asfarviridae…
- Only one virus species in the whole family
- dsDNA
- Cytoplasmic replication
- Large and complex
- Enveloped
- Highly resistant to wide pH range (4-15)
- Survives for months-years in refrigerated meat
- Only DNA virus that is an arbovirus (transmitted by ticks)
- Causes lethal haemorrhagic disease in pigs
- List A OIE notifiable disease
What is an arbovirus?
Term used to refer to viruses that are transmitted by arthropods
- need to replicate within the nucleus of these vector’s cells
e. g. ticks
Is African Swine Fever notifiable in NZ?
Yes
Describe African Swine Fever…
- Infects all members of the family Suidae
- Highly contagious lethal disease of pigs
- Asymptomatic in warthogs
- Clinical and post mortem signs are indistinguishable from classical swine fever (totally different family and also has a vaccine)
How far has African Swine Fever spread in less than a decade?
Across western Russia
- worrying because Russia is so close to Europe
Describe the epizootiology of African Swine Fever…
It has two different epidemiological patterns - transferred by ticks
- Sylvatic (circulates in wild animals only) cycle in wild african swine
- Epidemic and endemic cycles in domestic swine
Describe the Sylvatic cycle of ASF…
The virus cycles between the hosts: Wild pigs, domestic pigs and ticks
- Need a suitable vector for the disease to become enzootic in an area
Sexual transmission within the ticks
- mother to eggs
- from one virus developmental stage to another
Tick population is 25% infected
What symptoms do wild pigs show when infected with ASF?
None
- Asymptomatic
- Persistent Infection in wild pigs and ticks
How are pigs initially infected with ASF?
- Tick bites
OR - Ingestion / inhalation of infected material
- Feeding uncooked pig meat
How do infected pigs spread ASF?
They produce large amounts of virus in all body secretions and excretions
- Spread by:
- Aerosol
- Direct contact
- People
- Vehicles
- Other
If a pig recovers from ASF are they still infectious?
They remain carriers and shed the virus for their entire lives but don’t show clinical signs
What are the three forms of ASF clinical signs?
- Acute
- Subacute
- Chronic
What are ASF clinical signs?
- Bloody diarrhoea
- Hind leg paralysis
- Huddling
- Conjunctivitis
- Purple decolourisation on rump
- Staggering
What are some DDx for ASF?
- Classical Swine Fever
- Erysipelas
- Porcine dermatitis and nephropathy syndrome
- Salmonellosis
- Pasteurellosis
- All Septicaemic conditions
What samples do you collect for lab diagnosis of ASF?
- Tissues: spleen, kidney, liver, lymph nodes
- Anticoagulated blood for virus isolation
- Clotted blood for serology
How do you detect ASF or ASF components?
- Virus isolation (blood, spleen, kidney, liver)
- Fluorescent antibody test
- PCR
What serology tests do you need to diagnose ASF?
- Antiobodies to ASF appear 7-12 dots per inch
- No neutralisation
- No known cross-reactivity
- ELISA
Describe the pathogenesis of ASF…
Disseminated intravascular coagulation (DIC) with multiple haemorrhages in all tissues
- ASF replicates in macrophages and monocytes
- Modulation of signalling pathways in infected macrophages
- expression of a number of viral immunomodulatory (capable of modifying immune functions) proteins
Are neutralising antibodies made by pigs?
No
- not even in pigs that survive
Is there a vaccine available for ASF?
No not yet
How do you control ASF outbreaks?
- Difficult to control
- No vaccine
- Exclude wild pigs from domestic piggeries in enzootic areas
- Use tick killers and disinfectants
- Slaughter if spreads to unaffected country
- Burn carcasses
What are the risks of ASF to NZ?
- Imported frozen pig meat
- Imported live pigs
- Swill from passenger air crafts
- Ticks
- Wild pigs
Describe adenoviral replication…
- Replicate in the nucleus
- Produce intranuclear inclusion bodies - crystalline arrays of virions
- Virions release by cell lysis
- “Bunch of Grapes” cytoplasmic effects
