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Epi MT > Infectious Bursal Disease > Flashcards

Infectious Bursal Disease Flashcards

1
Q

causative agent of Infectious Bursal Disease

A

Birnaviridae

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2
Q

genome of Birnaviridae

A

dsRNA, 2 genome segments

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3
Q

Birnaviridae resistancy

A

no envelope
highly resistant

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4
Q

What does Avibirnavirus genus cause

A

Infectious bursal disease

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5
Q

what is the Infectious bursal disease

A

acute disease in 3-6 wk old chickens
with inflammation of the Bursa Fabricus and immunosuppresion

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6
Q

What strains of Infectious bursal disease is there?

A

classical (only found in australia)
new variant
very virulent

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7
Q

Serotypes of Infectious bursal disease

A

ST1: pathogenic
ST2: non-pathogenic, from turkey but may infect chickens too

serological cross-reaction but NO cross protection

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8
Q

Infectious bursal disease vaccines can be

A

hot
intermediate
mild

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9
Q

Infectious bursal disease virus hosts

A

mainly chickens
phaesents, turkey and ostrich

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10
Q

Infectious bursal disease epizootiology

A

PO
highly contagious
shedding within 1 day
contaminated environment main source of inf (mechanical transmission between farms)
no germinative route but eggshell inf with faeces

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11
Q

Infectious bursal disease pathogenesis

A

PO
macrophages of the gut & lymphoid tissue
prim. viraemia
liver
bursa of fabricus
sec. viraemia
spreading in body

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12
Q

Main target cells of Infectious bursal disease

A

premature B lymphocytes & other bursal cells

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13
Q

highest activity of Infectious bursal disease and why

A

2-8wks old, also highest activity of the bursa of fabricus

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14
Q

effect of infectious bursal disease virus infection at 2-8wks

A

5-100% mortality, but immuno-competence after recovery

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15
Q

effect of infectious bursal disease virus infection at 0-3wks

A

0-30% mortality, permanent immunosuppression

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16
Q

effect of infectious bursal disease virus infection above 8wks

A

no CS

17
Q

why does an infection at a young age of Infectious bursal disease cause immunosuppression

A

damage of Bcell receptor expression
weak immune resp against othe Ag
inefficient vaccination

18
Q

what causes the signs of acute Infectious Bursal disease

A

immune-complex deposition and necrotizing agents

19
Q

what influences the severity of Infectious Bursal disease

A
  • age (2-8wks)
  • maternal Ab
  • breed of chicken (layers)
  • virulence of virus strain
  • antigenicity of virus (wild type, vaccine, specificity of yolk immunity)
  • immunosuppression (mycotoxins)
20
Q

Infectious Bursal disease CS age

A

3-6 wks (after 2-3 dys incubation)

21
Q

Infectious Bursal disease CS

A
  • lethargy
  • watery diarrhea
  • swollen, bloddy vent, urate crystals on feathers around vent
  • anaemia
22
Q

Subclinical Infectious Bursal disease CS

A

immunosuppression

23
Q

Infectious Bursal disease patho of acute phase

A
  • bursa of fabricus
  • haemorrhages
  • nephritis
  • spleen (enlarged)
  • liver (necrotic foci, oedema)
  • thymus (lymphoid depletion in cortex)
  • BM: necrosis
24
Q

Infectious Bursal disease patho pf chronic phase

A
  • bursa of fabricus (atrophy, early involution)
  • signs of coinfection
25
Q

Infectious Bursal disease diagnosis

A

RT-PCR + sequencing

26
Q

Infectious Bursal disease DDx

A
  • newcastle D (any age, resp & CNS)
  • Bact. speticiaemia
  • Reticuloendotheliosis (older animals, tumors)
  • Chicken anaemia (no inflammation of bursa, only atrophy)
  • malabsorption syndrome (no inflammation of bursa)
  • Coccidiosis (SI & colon lesions)
27
Q

Infectious Bursal disease prevention

A

hygiene
disenfection of egg shells
decontamination of fomites

28
Q

When to vaccinate against Infectious Bursal disease

A

timing based on level of maternal Ab level of the flock

29
Q

which Infectious Bursal disease virus strains easily breaks through maternal antibody protection

A

vvIBDV

30
Q

Mild (strongly attenuated) IBDV vaccine strains

A
  • no bursal damage
  • efficacious only at lower or seronegative chickens
31
Q

Intermediate (moderatly attenuated) IBDV vaccine strain

A
  • mild bursa damage
  • efficacious at lower maternal antibody level
32
Q

hot (weakly attenuated) IBDV strain

A
  • pathognomic in seronegative chickens
  • efficacious at high maternal antibody levels
  • (determination of Ab levels is needed)
33
Q

which virus is used for the IBD vaccine

A

VP2 coding gene is cloned into turkey herpes virus vector

34
Q

IBD immune-complex vaccine

A

live virus + specific Ab
vaccine virus is protected from maternal Ab, multiplication is controlled, immune complex is captured by the spleen follicular dendritic cells

35
Q

IBD inactivated vaccines

A

booster vaccines, for layer parents
high, long-lasting immunity
given IM

36
Q

Live attenuated vaccine of IBD

A
  • drinking water (PO)
  • vaccine virus propagates to bursa
  • vacc. time is critical
  • protection depends on vaccine strain
37
Q

Recombinant vector vaccines (HVT)

A
  • in ovo or Sc in hatchery
  • will not propagate in the bursa
  • protection against VP2 of virus
  • DIVA
38
Q

IBD Immune-complex vaccines

A
  • In ovo or SC in hatchery
  • can propagate to bursa
  • full protection after vaccine take in bursa
  • compatible with Marek vaccine used in hatchery

Epi MT (15 decks)

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