Avian Influenza Virus Flashcards
What family does influenza belong to?
Orthomyxoviridae family
What is influenza A?
Causes influenza infections in both animals and people
Usually seasonal
has 8 segments with two strains
What is influenza B?
Has a more limited host range- only affects humans and seals
Causes seasonal influenza in humans
What is influenza C?
- Limited host range- only affects humans and pigs
- Rare infections in people- only 7 segments
What are the two major envelope proteins in the influenza A virus?
- Haemagglutinin, HA, H
- Neuraminidase, NA, N
What is influenza A subtyping based on?
the antigenicity
How many genome segments are found inside of influenza?
8
What is the main innate immune response of avian influenza?
It has a specific protein NS1
that blocks the production of interferon gamma
How many subtypes of HA are there?
18
How many subtypes of NA are there?
11
What is thought to be the main reservoir of all influenza
aquatic waterfowl
What are the main symptoms of LPAI ( low pathogenicity avian influenza)
- ruffled feathers
- loss in egg production
- reduced weight gain
Name five symptoms of high pathogencity avian infleunza
- failure to eat
- fever or noticeable increase in body temp
- mucus discharge
- diarrhoea
- neurological signs
Name four ways the avian influenza virus can be transmissed
- Direct-Direct contact
- contaminated faeces and bodily fluids
- contaminated feed and water
- vehicles, clothing and footwear
What samples of avian influenza may DEFRA take for testing?
- swabs (oro-pharyngeal)
- tissue samples
- blood samples
- carcass depending on the species
What control strategies may DEFRA put in place for avian influenza?
- Cull birds on infected premises
- may put a place in a restricted zone
- no movement of poultry, eggs etc
- no gatherings of poultry
Name four ways to reduce human to animal transmission
- Surveillance
- Reduce the exposure
- Seek medical assistance
- Education of the public
What is the inactivated vaccine given to humans?
- Strain that grows well in eggs
- typically given by intramuscular innoculation
What is the live attenuated vaccine given to humans?
- addition of mutations to make the vaccine sensitive
- adminsitered by an intranasal spray twice a year in the nasal passages
What occurs to the haemagglutinin when the virus enters an endosome?
- HA acidification
- Causes the core to loosen
- low pH then causes haemagglutin to fuse with the endosome and uncoat
What is the innate anti-viral response?
- Virus encodes a non-structural protein which antagonises the induction of type I IFN
- Prevents RIG-I activation (receptor for inteferon I)
- Prevents RIG-I signalling
What is the adaptive anti-viral response?
- Dendritic cells present the antigen to T lymphocytes in the lymph node
- T cells leave the lymph node, circulate in the blood and hone to the infection site
- IFN activates macrophages and other cells at the site of infection
- CD8 kills infected cells to stop the spread of infection
Name one example of low pathogenicity avian influenza
- H9N2
- Prevalent in Asia and the Middle East
- still causes production losses and is economically important
What two LPAI can mutate to become HPAI?
- H5
- H7
