Birniviridae

Question 1

What are the two genuses in family Birniviridae and what species do they infect?

Answer 1

Aquabirnivirus: salmonid fish
Avibirnavirus: chickens

Question 2

Describe the genome and virion of family Birniviridae

Answer 2

Non-enveloped, hexagonal, single shell with icosahedral symmetry
Two segments of linear double stranded RNA

Question 3

Where does family Birniviridae replicate?

Answer 3

Cytoplasm

Question 4

What disease is caused by avibirnavirus?

Answer 4

Infectious bursal disease (IBD)

Question 5

What is the primary target of IBD?

Answer 5

Lymphoid tissue with a special predilection for the bursa of Fabricius

Question 6

Which type of IBD is pathogenic to chickens, 1 or 2?

Answer 6

Serotype 1:
Variant viruses (no mortality)
Classical (10-50% mortality)
Very virulent (50-100% mortality)

Question 7

T or F: IBD is unstable in the environment

Answer 7

False! It is very stable
Can survive in poultry houses even after cleaning/disinfection
Detected in water/feed even after 52 days!

Question 8

How is IBD transmitted?

Answer 8

Virus is excreted by infected birds and then transmitted fecal-oral route

Question 9

What is the pathogenesis of IBDV?

Answer 9

Infected orally, replicates in gut-associated macrophages and lymphocytes in cecum and small intestine–> liver –> blood stream –> bursa of fabricius! Highest susceptibility is between 3-6 weeks
Can then either cause immunosuppression (depletion of B cells) or secondary viremia –> other tissues

Question 10

What is a ‘cytokine storm?’

Answer 10

IBDV can trigger INDIRECT T cell activation and DIRECT macrophage activation in the acute phase of this disease, results in death

Question 11

What are the clinical signs of IBD?

Answer 11

Distress, depression, ruffled feathers, diarrhea, anorexia, swollen bursa of fabricius, hemorrhages, dehydration

Question 12

What are the stages of the bursa as IBD progresses?

Answer 12

Acute: enlarged, edematous bursa
5 days in: bursa returns to normal size, may be hemorrhagic
8 days in: bursa atrophied and up to 1/8 normal size

Question 13

How are live IBD vaccines produced?

Answer 13

From fully or partially attenuated strains of virus, known as mild, intermediate, or intermediate plus

Question 14

Which type of vaccine strain cannot be used effectively in chicks with maternal derived antibodies until 4 weeks of age?

Answer 14

Mild vaccines, they will be neutralized

Question 15

Which vaccines can be given at earlier stages, depending on MDA titers?

Answer 15

Intermediate and intermediate plus!

Question 16

Describe the immune complex vaccine of IBD?

Answer 16

Live iBD vaccine virus + anti-IBDV antibody goes into the egg
A live recombinant vaccine uses a viral vector to express the VP2 antigen of IBDV in chickens has been licensed recently

Whatever the fuck that means^