Avian influenza

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Avian influenza

• Saliha Hammoumi
• CIRAD Montpellier, France

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Outline

• Influenza Virus description
• Influenza epidemiology
• Poultry / wild birds / humans
• Current projet TCP FAO
• Surveillance of AIV in wild birds in Africa,
  Middle-East and in Eastern Europe

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Influenza Virus
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Influenza virus

• Family Orthomyxoviridae
• Enveloped
• 8 segments single stranded (-) sense RNA
• Three main types
• Type A
• Multi-species
• Type B
• Human
• Type C
• Human and pig

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Influenza A Virus

• Multi-species
• Mammals (human, pig and horse)
• Birds
• The most virulent group
• Classification in subtypes by surface antigenes
• Hemagglutinine (H or HA) 16
• Neuraminidase (N or NA) 9
• All HxNy types in waterfowl

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Surface antigens and subtypes
Cleaves sialic acids and permits the liberation
of viral particles
Attachment site on host cells (receptor sialic
acid)
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Designation of influenza viruses

• Type/ species of the isolate if non human /place
  of isolation/ number of strain/year of isolation
  (subtype)
• A/Hong-Kong/1/68 (H3N2)
• A/eq/Miami/1/63 (H3N8)

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HA subtypes and host distribution
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Influenza variability antigenic drift
Spontaneous genetic mutations due to the absence
of proof-reading activity of the polymerase.
Selection of viruses mutated on H and/or N gene
due to selection pressure of antibodies
Epidemic
Conserved immunity
Antigenic modification
No antigenic modification
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Influenza variability antigenic shift

• New combinations of H and N can occur by
  reassortments of the RNA encoding H and N
  proteins when cells are coinfected with 2
  different sub-type viruses

People, pigs and aquatic birds are the principle
variables associated with the interspecies
transfer with pigs and ducks acting as  mixing
vessels  
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Pandemics
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Origin of the H5N1 bird flu
It is proposed that the H5N1 influenza virus that
infected humans in Hong Kong in 1997 is a
re-assortant The HA gene have come from
A/Goose/Guandong/1/96 (H5N1) influenza virus and
the internal genes from a EurAsian avian
influenza virus.
Webster 2002
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Avian influenza

• Pathogenicity based on disease severity on
  poultry and/or genetics
• Low pathogen (LPAI)
• Subtypes H1 to H16
• High pathogen (HPAI)
• Some strains of H5 or H7 subtypes (possibly H6 or
  H9)
• Some LPAI strains of H5 or H7 subtypes may mutate
  in HPAI

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Hemagglutinine and HPAI
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Influenza epidemiology
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(No Transcript)
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Transmission

• Source of infection
• Poultry
• Migratory waterfowl
• Transmission
• Droppings, secretions from the eyes and nose of
  infected birds
• Shared drinking water or food
• Manure, equipment, vehicles and crates

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HPAI Morbidity / Mortality

• Merely 100 in commercial poultry flocks
• Death within 2 to 12 days after the first signs
  of illness

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Cumulative H5N1 cases in poultry and wild birds
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Current situation in poultry and wild birds
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Cumulative H5N1 human cases
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Current situation in humans
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• TCP FAO Surveillance of AIV in wild birds in
  Africa, Middle-East and in Eastern Europe

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Sampling sites
number of tracheal and cloacal samples collected
per site
analysed samples analysis in process
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Sampling procedure
-80C
Shipment under dry ice
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Laboratory analyses procedure
Mix
88 samples pooled in a 96 deep well plate 6
ten-fold dilutions of A/PR/8/34
Sample sorting
Discard Swabs
RNA extraction of 100 µl of 88 samples in 50 min
in a final volume of 50 µL

• Influenza A Q RT-PCR M gene
• Primers M25, M-124 and the probe M25 (Spackman
  et al, 2002)
• Brilliant QRT-PCR one-step Master mix kit
  (Stratagene)

Positive samples

• Influenza H5 and H7 Q RT-PCR
• primers and probes recommended by the reference
  laboratory VLA (Weybridge, UK)
• one-step RT-PCR kit (Qiagen)

Positive samples
RT-PCR on HA cleavage site
Sequencing and pathotyping