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VIROLOGY > Circoviruses > Flashcards

Circoviruses Flashcards

1
Q

What are some examples of Circoviridase?

A
  • Chicken anemia virus (CAV)
  • Porcine circovirus (PCV)
  • Psittacine beak and feather disease virus (PBFDV)
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2
Q

What are the features of circoviruses?

A
  • Virions are NON-enveloped, spherical in outline with ICOSAHEDRAL symmetry
    o often appear in infected cells and free in disease material as ‘string of pearls’
    o genome consists of ss ambisense or positive DNA
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3
Q

Porcine circoviruses (PCVs): characteristics

A
  • unique small ssDNA virus
  • 3 open-reading frames
  • Genetically different from PCV1
  • Came from bananas
  • *UofS found connection=brought in lots of $$$
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4
Q

Circovirus replication HIGHLIGHTS

A
  • Virus enters ACTIVELY DIVIDING CELL (s-phase) via endocytosis of CHONDROITIN SULPHATE-virus complex
  • Uncoated in endosome
  • Uses cellular DNA polymerase to make dsDNA intermediate for transcription of viral mRNA
  • Translation of non-structural protein Rep
  • Translation of capsid protein
  • Genome replicated by complex ‘rolling circle’ scheme
  • Virus assembles in NUCLEUS
    o Accumulation lead to LYSIS of cell? Necrosis or apoptosis?
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5
Q

What is an open reading frame (ORF)?

A
  • Region from start codon to stop codon
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6
Q

What are eukaryotic genes ‘interrupted’ by? (‘ORF’)

A
  • Intervening noncoding sequences=INTRONS
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7
Q

Prokaryotes and ORF

A
  • ORF and coding sequence (CDS) are the same
  • Eukaryotes: ORF may contain introns, CDS is what codons are actually translated
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8
Q

What is the pathogenies of PCV2 infections?

A
  • Fecal oral transmission
  • Virus enters cell by endocytosis
  • *not sure of primary target cell
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9
Q

What co-factors play a role in the pathogenesis of PCV-2 associated diseases? PCV-2 is necessary, but insufficient cause (NEED SOMETHING ELSE TO TAKE IT ‘FURTHER’)

A

o Many infectious agents
o Variation?
- Non-infectious
o Management practices: vaccination
o Genetics
o Diets

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10
Q

What is the role of host genetics?

A
  • Some lines are hypersusceptible to the virus
  • Ex. if go for performance trait=but get a linked more susceptibility to a disease
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11
Q

What are the PCV-2 associated diseases?

A
  • Post-weaning multisystemic wasting syndrome (PMWS)
  • Porcine respiratory disease complex (PRDC)
  • Hepatic
  • Renal
  • Gastro-enteric
  • Cardiac: cardiomegaly
  • Reproductive: mostly gilts, poor immunity
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12
Q

What constitutes a diagnosis of PCV-2 associated disease in an individual pig?

A
  • Clinical signs
  • Typical lesions
  • Detection of PCV2 antigen or DNA in lesions (immunohistochemistry and in situ hybridization)
  • *NEED ALL 3!
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13
Q

Clinical signs of PCV-2 associated disease

A
  • Wasting
  • Respiratory
  • Diarrhea
  • Palor/ichterus
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14
Q

Typical lesions of PCV-2 associated disease

A
  • Granulomatous lymphadenitis with lymphoid depletion
  • Interstitial pneumonia
  • Hepatitis
  • Nephritis
  • Enteritis
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15
Q

What are the 2 approaches to Immunoprophylaxis against PCV-2?

A
  • Vaccinate piglet (adaptive immunity)
  • Vaccinate sow (passive immunity)
  • *various vaccines available in Canada (table in slides)
    o All dead vaccines
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16
Q

Cross-genotype protection

A
  • There is only one serotype but may be differences in genotypes
  • *to date: there is a good level of cross protection from the original isolate and others
17
Q

PCV2 vaccines can reduce effects of subclinical and co-infections

A
  • *if vaccinate herd=minimize production loss
18
Q

PCV-3 and PCV-4

A
  • PCV-3: lots of questions still (no vaccine yet)
  • PCV-4: even less known
  • *moving target (‘job security for vets)
19
Q

What are the features of psitaccine beak and feather disease (PBFD)?

A
  • Genetic differences of isolates infecting different species of psitaccine
  • *secondary viral, fungal, bacterial or parastitic infections often occur as a result of diminished immunity
20
Q

Clinical signs of psitaccine beak and feather disease

A
  • Irreversible loss of feathers
  • Shedding of developing feathers
  • Development of abnormal feathers
  • New pinched feathers
  • Loss of powder down
  • Overgrown or abnormal beak
  • IMMUNOSUPPRESION: rapid weight loss and depression
21
Q

How is PBFD diagnosed?

A
  • Skin biopsy
  • Surgical biopsy of feather and shaft
    o Not all are affected simultaneously
  • *IHC
  • **PCR : important for before the feather lesions develop
  • *NEED TO SEE 3 things
22
Q

What are the 3 criteria for a case of PBFDV?

A
  • Clinical signs
  • Typical lesions
  • Evidence of VIRUS in the lesions
23
Q

When should PBFD be considered?

A
  • In any bird suffering from ABNORMAL feather loss or development
24
Q

What is recommended to test an individual bird?

A
  • Whole blood sample + cloacal swab or feathers
  • *if positive: placed in quarantine and re-tested after 4-6 weeks
    o If negative: test 3rd time after 4-6 hours
25
Q

What are post-mortem samples for PBFD?

A
  • Liver
  • Spleen
  • Kidney
  • Feather samples in a sterile container
  • *postmortem swabs may also be submitted
26
Q

Environmental testing with swabs for PBFD?

A
  • Aviaries
  • Countertops
  • Fans
  • Air-filters
  • Nest-boxes
  • *extremely effective in determining presence of PBFD DNA in the environment
27
Q

Interpretation of PCR results for PBFDV in blood can be problematic

A
  • Increased load (Low CT value)=associated with worse disease
    o don’t just kill the bird though
  • some test positive but don’t show clinical signs
  • some test negative b/c the fought off infection (30-90 days)
  • **important to re-test positive birds 60-90 days after initial test
28
Q

PBFD vaccine

A
  • hope for effective vaccine, no news yet
  • *market: not that big
29
Q

What are the features of chicken anemia virus (CAV)?

A
  • Really IMPORTANT
  • Age susceptibility/resistance >2 weeks of age
  • Many animals packed in together=lots of viral evolution
  • *no effective vaccine
  • *maternal antibodies protect from disease NOT infection
30
Q

How is CAV transmitted? (2)

A
  • Horizontally by direct contact and contaminated fomites
  • Vertically through egg
31
Q

What are the signs of acute immunosuppressive disease from CAV in young chickens?

A
  • Anorexia
  • Depression
  • Anemia
  • wasting
32
Q

How is CAV diagnosed?

A
  • Presumptive on history, clinical signs, lesions
  • Serology (commercial ELISA)
  • Demonstration of virus in tissues
33
Q

Canine circovirus

A
  • Not much of a clinical concern currently
  • Bloody diarrhea in dogs
  • Maybe associated with respiratory disease in dogs (‘job security’)
34
Q

Human transplants from genetically engineered pigs

A
  • Increasing concern for PCV-2 in xenotransplantation
  • Not a major concern yet: not great evidence that PCV-2 can replicate in humans
    o Probably wont cause disease systemically, still could cause disease in the transplanted organ (ex. heart)
  • *pigs can be screened for this though!

VIROLOGY (12 decks)

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