Infectious Bursal Disease

Question 1

causative agent of Infectious Bursal Disease

Answer 1

Birnaviridae

Question 2

genome of Birnaviridae

Answer 2

dsRNA, 2 genome segments

Question 3

Birnaviridae resistancy

Answer 3

no envelope
highly resistant

Question 4

What does Avibirnavirus genus cause

Answer 4

Infectious bursal disease

Question 5

what is the Infectious bursal disease

Answer 5

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

Question 6

What strains of Infectious bursal disease is there?

Answer 6

classical (only found in australia)
new variant
very virulent

Question 7

Serotypes of Infectious bursal disease

Answer 7

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

serological cross-reaction but NO cross protection

Question 8

Infectious bursal disease vaccines can be

Answer 8

hot
intermediate
mild

Question 9

Infectious bursal disease virus hosts

Answer 9

mainly chickens
phaesents, turkey and ostrich

Question 10

Infectious bursal disease epizootiology

Answer 10

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

Question 11

Infectious bursal disease pathogenesis

Answer 11

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

Question 12

Main target cells of Infectious bursal disease

Answer 12

premature B lymphocytes & other bursal cells

Question 13

highest activity of Infectious bursal disease and why

Answer 13

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

Question 14

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

Answer 14

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

Question 15

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

Answer 15

0-30% mortality, permanent immunosuppression

Question 16

effect of infectious bursal disease virus infection above 8wks

Answer 16

no CS

Question 17

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

Answer 17

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

Question 18

what causes the signs of acute Infectious Bursal disease

Answer 18

immune-complex deposition and necrotizing agents

Question 19

what influences the severity of Infectious Bursal disease

Answer 19

• 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)

Question 20

Infectious Bursal disease CS age

Answer 20

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

Question 21

Infectious Bursal disease CS

Answer 21

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

Question 22

Subclinical Infectious Bursal disease CS

Answer 22

immunosuppression

Question 23

Infectious Bursal disease patho of acute phase

Answer 23

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

Question 24

Infectious Bursal disease patho pf chronic phase

Answer 24

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

Question 25

Infectious Bursal disease diagnosis

Answer 25

RT-PCR + sequencing

Question 26

Infectious Bursal disease DDx

Answer 26

- 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)

Question 27

Infectious Bursal disease prevention

Answer 27

hygiene disenfection of egg shells decontamination of fomites

Question 28

When to vaccinate against Infectious Bursal disease

Answer 28

timing based on level of maternal Ab level of the flock

Question 29

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

Answer 29

vvIBDV

Question 30

Mild (strongly attenuated) IBDV vaccine strains

Answer 30

- no bursal damage - efficacious only at lower or seronegative chickens

Question 31

Intermediate (moderatly attenuated) IBDV vaccine strain

Answer 31

- mild bursa damage - efficacious at lower maternal antibody level

Question 32

hot (weakly attenuated) IBDV strain

Answer 32

- pathognomic in seronegative chickens - efficacious at high maternal antibody levels - (determination of Ab levels is needed)

Question 33

which virus is used for the IBD vaccine

Answer 33

VP2 coding gene is cloned into turkey herpes virus vector

Question 34

IBD immune-complex vaccine

Answer 34

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

Question 35

IBD inactivated vaccines

Answer 35

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

Question 36

Live attenuated vaccine of IBD

Answer 36

- drinking water (PO) - vaccine virus propagates to bursa - vacc. time is critical - protection depends on vaccine strain

Question 37

Recombinant vector vaccines (HVT)

Answer 37

- in ovo or Sc in hatchery - will **not** propagate in the bursa - protection against VP2 of virus - DIVA

Question 38

IBD Immune-complex vaccines

Answer 38

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