Birnaviridae

Question 1

General characteristics

Answer 1

nonenveloped, hexagonal, single shell with icosahedral symmetry
2 segments linear dsRNA (designated as A and B)

Question 2

replication takes place where

Answer 2

cytoplasm

Question 3

infectious bursal disease (IBD)

Answer 3

acute, highly contagious infection

young chickens

Question 4

primary target of IBD

Answer 4

lymphoid tissue

special predilection for bursa of fabricius (cloacal bursa)

Question 5

Bursa of fabricius development

Answer 5

develops from out pouching of hindgut

B cell development

Question 6

IBD serotype 1

Answer 6

pathogenic to chickens
3 antigenic subgroups: variant viruses (no mortality)
classic or standard viruses (10-50% mortality)
very virulent viruses (50-100%) mortality

Question 7

IBD serotype 2

Answer 7

asymptomatic infections in chickens and turkeys

Question 8

IBD transmission

Answer 8

contact, fecal-oral
excreted by infected birds
very stable in environment
can survive in poultry houses after cleaning and disinfection
detected in water and feed after 52 days

Question 9

IBD pathogenesis

Answer 9

replication in gut associated macrophages and lymphocytes in ceca and small intestine,
go to liver,
go to bloodstream,
target organ is BF at max development (specific source for mature B lymphocytes)
max virus replication and depletion of B cells (necrosis and apoptosis)

can lead to: 
secondary viremia,
localization in other tissues,
triggering of INdirect t cell activation and direct macrophage activation leading to cytokine storm-> acute phase-> death,
immunosuppression

Question 10

When is highest susceptibility to IBD

Answer 10

3-6 weeks

Question 11

Recovered birds or subclinical cases

Answer 11

Immunosuppression

diminished antibody response and increased susceptibility to range of opportunistic infectious agents

Question 12

destruction of B cells causes

Answer 12

apoptosis, humoral immunosuppression

Question 13

indirect activation of t cells causes

Answer 13

cell mediated immunosuppression

Question 14

CS IBD

Answer 14

distress, depression, ruffled feathers, diarrhea, anorexia, dehydration, swollen bursa fabricius with hemorrhages

Question 15

What you see during acute stage

Answer 15

enlarged edematous bursa

Question 16

what you see 5 days post infection

Answer 16

bursa returns to normal size, may be hemorrhagic

Question 17

what you see 8 days post infection

Answer 17

bursa atrophied and up to 1/8 normal size

Question 18

Immune complex vaccines

Answer 18

live IBD vaccine virus + anti-IBDV antibody
in ovo
live recombinant vaccine that uses viral vector (herpes virus of turkeys) to express VP2 Ag of IBDV

Question 19

Vaccines available

Answer 19

Live IBD vaccine: from fully or partially attenuated straings, mild, intermediate, or intermediate plus(hot)
Mild vaccine strains- no bursal lesion, can tbe effectively used in chicks with maternal Ab (until 4 wks age)
intermediate and hot- less affected by MDA, some succes at earlier stages