Avian Influenza Virus

Question 1

How is Influenza A subtyped ?

Answer 1

based on antigenicity of the two major envelope proteins (haemagglutinin, HA and neuraminidase, NA)
- 18 HA (16 that affect birds)
- 11 NA (9 that affect birds)

Question 2

Influenza A structure

Answer 2

(-) ssRNA with various proteins encoded by various genome segments

Question 3

Influenza A lifecycle

Answer 3

1. entry into cells (binding –> endocytosis –> HA acidification –> fusion –> uncoating –> nuclear import)
2. RNA transcription
3. RNA segment unpacking
4. virus budding

Question 4

Influenza A pathogenicity

Answer 4

encodes for non-structural protein 1 (NS1) which is able to antagonise the induction of Type I IFN
adaptive immune response (T-cell reactions)
humoral immunity

Question 5

How does Influenza A evade the host’s immune system

Answer 5

surface proteins can change due to mutations
they can also alter the epitopes

Question 6

How are influenza viruses named ?

Answer 6

virus, genera (A/B/C/D), species it affects, place of isolation, isolate number, date and subtype.

IN THIS ORDER !!

Question 7

How does influenza transmission occur ?

Answer 7

direct contact
contaminated faeces and bodily fluids
contaminated feed and water
vehicles, clothing and footwear

NOT airborne

Question 8

What is the main reservoir for influenza A ?

Answer 8

aquatic waterfowl

Question 9

Define LPAI

Answer 9

low pathogenicity avian influenza

mild disease with little to no symtpoms

Question 10

Define HPAI

Answer 10

high pathogenicity avian influenza
a much more severe disease with a high mortality rate
(LPAIs can mutate)

Question 11

What are the CS of avian influenza

Answer 11

anorexia, dehydration, reduced laying, fever, swollen head and eyes (oedema), blue-ish discolouration of comb and wattle, diarrhoea, mucus discharges, resp distress, neuro signs

Question 12

Is Avian influenza notifiable ?

Answer 12

yes

Question 13

Control measures ?

Answer 13

anyone keeping >50 birds int he UK must register them
cleaning and disinfecting
fully enclosed water and feed
culling infected birds
restricted zones in place
no movement of poultry, eggs or carcasses
surveillance

Question 14

What samples are used for testing ?

Answer 14

oro-pharyngeal and cloacal swabs
tissue samples
blood samples
entire carcass

Question 15

Name some relevant lineages

Answer 15

H5N1 Gs/Gd
H6Nx
H7N9

Question 16

Are there any vaccines available ?

Answer 16

yes
inactivated and live vaccines are licensed - not currently permitted in the UK (only for zoo birds)

Question 17

Treatment ?

Answer 17

antivirals are used to treat or prevent infection, primarily neuraminidase inhibitors
high levels of resistance :(