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
Describe the structure of Adenoviruses…
- Penton fibres project from icosahedral vertices
- Each fibre has a terminal knob
- These knobs stick together some mammalian RBCs
- can use haemagglutination test (HA)
What are some common properties of Adenoviruses?
- Resistant in the environment
- Readily transmitted on fomites
- Provoke strong humoral immune responses
- Can persist for a long period
- Widespread
- Host Specific
- Relatively non-pathogenic
- Can cause disease in immunocompromised hosts
- Some are oncogenic in rodents
- Infect cells in respiratory and GI tracts
Where can adenoviruses persist for long periods?
- Pharyngeal lymphoid tissues
- Kidney tubule cells
- Intestinal cells
What are some diseases caused by adenoviruses?
- Canine adenoviruses 1 and 2
- Equine adenoviruses
- Egg drop syndrome
- Inclusion body hepatitis
- Haemorrhagic enteritis of turkeys
- Marble spleen disease of pheasants
- Quail Bronchitis
What are the names for canine adenoviruses 1 and 2?
- Infectious canine hepatitis (CAdV-1)
- - Respiratory Disease (CAdV-2)
Describe Canine Adenovirus 1…
Infectious canine hepatitis
- Dogs (puppies espec) , foxes, wolves. coyotes, skunks, bears are susceptible
- Acute hepatitis
- Many subclinical infections occur
Describe the infection of CAdV-1…
- Infection by nasopharyngeal, oral or conjunctival routes
- Local replication in tonsils or Peyer’s patches
- Spread to many tissues
- Replication
- Transmission
- Excretion in faeces, saliva and urine
- Endothelial cells cause haemorrhages
- Parenchymal cells cause necrotic lesions
What is peracute CAdV-1 disease?
Death in 3-4 hours
No symptoms
What is acute CAdV-1?
- Incubation period of 4-9 days
- Fever
- Depression
- Loss of appetite
- Vomiting
- Abdominal pain
- Tachycardia
- Leukopenia
- Prolonged clotting time
- DIC
- Bloody Diarrhoea
- Petechial haemorrhages on gums
- Pale Mucous Membranes
- May be Fatal
What is “blue eye”?
Corneal Opacity that develops in 25% of dogs with acute CAdV-1
- develops 7-10 days after apparent recovery
- usually disappears spontaneously
What is the mortality rate in dogs with CAdV-1?
Puppies: 100% mortality
Adults: 10-30% mortality
Do dogs that have recovered from CAdV-1 shed the virus?
Yes
- for several months
- especially in urine
How is CAdV-1 diagnosed?
- Clinical Signs
- Clinical Pathology
- Gross Pathology
- Histopathology
- Rising antibody titres
- Virus Isolation
- Viral Antigen in tissues
- Viral DNA in PCR
What is CAdV-2 a contributing factor to?
Infectious canine laryngotracheitis (kennel cough)
Describe the vaccination against CAdV-1…
Inactivated vaccine
- Live attenuated no longer used because of complications
Describe the vaccination against CAdV-2…
Live Attenuated
- also protects against CAdV-1 (cross-protection) because their antigenic properties are similar
Describe Equine Adenoviruses….
- Most infections are asymptomatic
- May contribute to equine respiratory disease
- fever, depression, nasal discharge, cough
- Self- limiting
What is SCID?
Severe combined immunodeficiency
- Absence of both T and B cells
- Destruction of cells in many tissues and multi-organ failure
- Death at ~3 months old
What are the clinical features of acute ASF?
- Fever
- Early leucopaenia and thrombocytopaenia
- Reddening of skin extremities
- Anorexia, listlessness, cyanosis, incoordination
- Increased pulse and RR
- Vomiting, diarrhoea and eye discharges
- Death up to 20 days
What are the clinical features of subacute ASF?
- Less severe clinical signs
- 5-30 duration
- Abortion in pregnant sows
- Death within 15-45 days
- Low mortality rate
What are the clinical features of chronic ASF?
- Weightloss
- Irregular peaks of temperature
- Respiratory signs
- Necrosis in areas of skin
- Chronic skin ulcers
- Arthritis
- Pericarditis
- Adhesions of lungs
- Swelling over joints
- Develops over 2-15 months
- Low mortality
