Circoviridae

Question 1

Describe the family circoviridae.

Answer 1

-circular single stranded DNA genomes
>genus circovirus = circular single stranded ambisense DNA
-virus replication occur in actively dividing cell
-virions are stable = resist 60c for 30min & pH3-9
-post weaning multisystemic wasting syndrome (PMWS)

Question 2

Describe PMWS.

Answer 2

1. Etiology
   -porcine circovirus 2 (PCV2)
2. Host
   -pigs
   -4-6 wk of age or 2-3 wk post weaning
3. Transmission
   -wide spread
   -fecal oral (most common)
   -found in all secretions (feces, nasal, urine, nasal secretion, salvia)
   -vertical transmission (trans placental inf)
   >inf during 1st & 2nd trimester = fetal death & reabsorption/aborted fetus w cardiac congestion
   >inf durning 3rd trimester = min effect on fetus
   -stable & survive on fomites for long periods
4. Pathogenesis
   -individual to coalescing foci of granulomatous inflam in lymphoid tissue, lung, liver, kidney, heart, intestine w botryoid grape like intra cytoplasmic inclusion bodies in virus inf macs
   -lymphoid depletion & lymphopenia in peripheral blood
   >loss of B & T cells = no direct effect of PCV2 on lymphocytes (cause is unknown)
5. CS
   -common: subclinical, lethargy, weight loss, cough, dyspnea, slow growth, lymphadenopathy, diarrhea, skin discolor, congenital tremor, icterus
   -co inf w porcine parvovirus (PPV): repro & respiratory virus (PRRSV), SIV, mycoplasma hyo pneumoniae, opportunistic bacteria cause disease & more lesions

Question 3

Describe PMWS diagnosis & treatment.

Answer 3

1. Diagnosis
   -serological assay = most pigs are sero positive -> antigen detection is not valuable
   -detection of PCV2 nucleic acids by PCR
2. Treatment
   -chimeric vaccine = new gen vaccine to utilize the non pathogenic porcine circovirus 1 as a genetic backbone for the expression of the immunogenic capsid protein of PCV2
   -inactivated or baculovirus expressed vaccine = virus like particles that include the capsid protein of PCV2
   -sow vaccine = antepartum

Question 4

Describe PDNS.

Answer 4

‘Porcine dermatitis & nephropathy syndrome’
-associated w PCV2
-sporadic
-in older piglets
-CS: necrotizing skin lesions, vasculitis, fibrinous glomerulonephritis

Question 5

Describe family Anelloviridae general characteristics.

Answer 5

Genus: Gyrovirus -> ‘chicken infectious anemia virus’
-circular, single stranded neg sense DNA
-12 trumpet like structure
-host: contagious in young chicken (2-4wk)
>older chicken more resistant
-transmission:
>shed in feces & feather dander
>horizontal transmission thru inhalation or oral exposure
>vertical thru egg
>environ stable in fomite for long period

Question 6

Describe the chicken infectious anemia virus pathogenesis.

Answer 6

-sites of CAV replication:
>hemocytoblasts in BM -> anemia
>precursor T cell in cortex of thymus -> immunosuppresion
>dividing CD4 & CD8 cell in spleen
-apoptin protein of CAV -> apoptosis & destroy inf lymphocyte s
-immunosuppresion & aplastic anemia
>blood is watery & clot slowly bc thrombocytopenia
-bird vulnerable to secondary bacterial & fungal inf
-virus replicate in oviduct of chicken regulated by estrogen -> efficient vertical transmission

Question 7

Describe chicken infectious anemia clinical signs.

Answer 7

1. Anorectic, lethargic, depressed, dec body weight gain, pale
2. PCV low
3. SQ hemorrhage & skeletal hemorrhage = pale muscles

Question 8

Describe CAV diagnosis.

Answer 8

-CS
-exam blood: low PCV, total erythrocyte count reveal anemia, thrombocytopenia, watery blood, clot slowly
-necropsy
-histopath
-serology = ELISA, neutralization, FAT
-virus isolation
-PCR, RT PCR

Question 9

Describe CAV vaccination.

Answer 9

-immunity to CAV is complex
-presence of Ab in breeder dec vertical & horizontal transmission
-aim to protect progeny from vacc breeder from early inf via maternal Ab
-live vaccine = vacc Ab neg breeder flock before start of egg prod
-administer via inj or addition into water
-synergism between CAV & other immunosuppressive virus like Mareks - control of latter is IMP