FAO GUIDELINES FOR SURVEILLANCE OF PANDEMIC H1N1/2009 AND OTHER INFLUENZA VIRUSES IN SWINE POPULATIONS - PowerPoint PPT Presentation

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FAO GUIDELINES FOR SURVEILLANCE OF PANDEMIC H1N1/2009 AND OTHER INFLUENZA VIRUSES IN SWINE POPULATIONS

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11 june 2009. fao guidelines for surveillance of pandemic h1n1/2009 and other influenza viruses in swine populations – PowerPoint PPT presentation

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Title: FAO GUIDELINES FOR SURVEILLANCE OF PANDEMIC H1N1/2009 AND OTHER INFLUENZA VIRUSES IN SWINE POPULATIONS


1
FAO GUIDELINES FOR SURVEILLANCE OF PANDEMIC
H1N1/2009 AND OTHER INFLUENZA VIRUSES IN SWINE
POPULATIONS
  • Giancarlo Ferrari, Julio Pinto, Nick Honhold, Jim
    Zingeser, Gwenaelle Dauphin, Mia Kim, Klaas
    Dietze, Joseph Domenech and Juan Lubroth
  • http//www.fao.org/AG/AGAInfo/programmes/en/empres
    /AH1N1/docs/h1n1_guidelines_fao.pdf

2
Influenza A viruses
  • Family of Orthomyxoviridae
  • Single stranded RNA (negative sense)
  • Classification based on Haemoagglutinin (HA
    from H1 to H16) and Neuroaminidasis (NA from N1
    to N9)

3
Influenza A viruses
  • The nucleic acid is composed by 8 distinct
    segments
  • Those 8 segments recognize gene tracts that
    encode for 10 different proteins

4
Influenza A viruses
  • The HA gene encodes the haemagglutinin (HA)
  • The NA gene encodes the neuraminidase (NA)
  • The NP gene encodes the nucleoprotein (Influenza
    A, B, and C viruses have different
    nucleoproteins)
  • The M gene encodes two proteins a matrix protein
    (M1) and an ion channel (M2) spanning the lipid
    bilayer
  • The NS gene encodes two different non-structural
    proteins (namely NS1 and NS2, also known as NEP).
    These are found in the cytoplasm of the infected
    cell but not within the virion itself
  • The remaining three segments (PA, PB1 and PB2)
    encode for each of the 3 corresponding subunits
    of the RNA polymerase (PA, PB1 and PB2)

5
Influenza A viruses
  • Apparently a triple re-assortment (H3N2
    human/avian/swine) was started to be observed
    early in 1997-1998 (Neumann G. et al, 2009 Smith
    G.J.D. et al, 2009 Nature, vol 459 2009) which
    spread widely within North American pig
    population
  • Co-circulation and mixing of this triple H3N2
    re-assorted virus with well established swine
    lineages has generated further re-assorted H1N1
    and H1N2 virus in pigs that sporadically have
    infected humans

6
Influenza A viruses
  • What is new with the novel type A H1N1 ?
  • The novel virus possess
  • PB2 and PA genes of North America avian origin
  • PB1 gene of a human H3N2 virus
  • HA, NP and NS genes of classical swine virus
    origin
  • NA and M genes of Eurasian avian-like swine
    origin
  • This combination of gene segments had never been
    observed before.

7
Role of pigs
  • Pigs may play an important role in the ecology of
    influenza virus as mixing vessels
  • Determinants of host susceptibility (in humans
    and avian species) is the presence and
    distribution of specific acid sialic receptors
    for the HA protein of the influenza virus
  • The two most common receptors are the SA?2,6Gal
    (prevalent on epithelial cells of human trachea)
    and SA?2,3Gal (prevalent on epithelial cells in
    the intestinal tract of waterfowl, main
    replication site of avian influenza viruses)

8
Role of pigs
  • The reason why pigs are suggested to be a major
    mixing vessels of human and avian influenza virus
    is because they express high levels of both
    SA?2,6Gal and SA?2,3Gal in their upper
    respiratory epithelium
  • If simultaneously infected with human influenza
    and avian influenza virus a re-assortment could
    occur between the two viruses resulting in a
    third new virus

9
Role of pigs
  • It is noteworthy to mention that the
    susceptibility of humans to Highly Pathogenic
    Avian Influenza H5N1 correlates to the expression
    of SA?2,3Gal in bronchiole and alveolar type II
    cells in the lung (in fact in humans pneumonia is
    commonly seen and not an upper respiratory tract
    infection where those receptors are not present).

10
Role of pigs
  • While the origin of the implicated virus is still
    a question mark there is ample evidence of
    human-to-human transmission and influenza viruses
    have the potential to be transmitted to pigs
  • In this regard the first report of the pandemic
    A/H1N1 was from Canada

11
Role of pigs
  • More recently the novel H1N1 has been identified
    in a pig farm in Argentina, Chile, Australia,
    Norway
  • It has appeared plausible that pigs may have been
    acquired the infection for having been exposed to
    infected humans
  • Information available so far suggest that the
    disease in pigs is mild.

12
Role of pigs
  • Field observations and preliminary results of
    inoculation studies in pigs with the pandemic
    A/H1N1 strain done in the Veterinary Laboratories
    Agency (VLA) have shown that pigs are susceptible
    to the A/H1N1 virus and show typical signs of
    influenza
  • No mortality was observed
  • Peak shedding was noted mainly via nasopharyngeal
    route 3-5 days post infection
  • Transmission to other pigs occurred.

13
Guidelines for surveillance
  • Drafted following investigation in Mexico in
    response to member country requests for guidance
    and in support of developing TCPs
  • Intended to be a dynamic document in support of
    the recommendations by OIE/FAO/WHO to strengthen
    surveillance of respiratory syndromes in pigs
  • Current limitations of guidelines include
  • Guidance on what to do if virus is found to be
    generated in concert with OIE
  • Other species not presently included

14
Guidelines for surveillance
  • In general, most countries do not consider swine
    influenza virus infections as a high priority in
    relation to other animal and public health
    problems
  • There has been some increased pig and poultry
    surveillance activities, particularly in Europe
    and northern America

15
Guidelines for surveillance
  • In relation to the occurrence of human cases
  • To demonstrate absence of the Pandemic H1N1/2009
    virus in pigs
  • To detect the pandemic H1N1/2009 virus in swine
    in relation to respiratory syndromes

16
Guidelines for surveillance
  • Epidemiologic unit vs individual unit of
    observation
  • Constituted by a group of pigs that are
    physically confined within the same space with
    frequent contact between any other animal present
    in this physical space
  • Shed vs pen vs yard
  • Individual units matching case definition to be
    sampled according to criteria indicated

17
Guidelines for surveillance
  • Develop case definition
  • e.g. a cluster of clinical cases in pigs showing
    fever or sneezing or coughing or nasal or ocular
    discharge in at least one individual observation
    unit, developed within a one-week period and
    affecting at least 10 of the animals present in
    the unit

18
Guidelines for surveillance
  • Pigs vs humans (or viceversa)
  • Epidemiological investigations of human cases of
    the Pandemic H1N1/2009 influenza virus by tracing
    back potential contact(s) with pig herds to
    investigate if pigs are infected
  • Veterinary and Public Health authorities should
    coordinate efforts at the national and local
    level to standardize epidemiological
    investigations at the animal-human interface

19
Guidelines for surveillance
  • Pigs vs humans (or viceversa)
  • Contact with live animals is considered a risk
    factor
  • Consumption of pork products is not
  • Window period of exposure should be identified in
    order to optimize which holdings to be
    investigated (e.g. Mexico defined timely exposure
    as within 2 weeks preceding onset of symptoms)

20
Guidelines for surveillance
  • Farms categorized as C1 or C2 are eligible for
    the collection of nasal swabs (for virological
    analysis)
  • If farm categorized as C3, would not eligible for
    immediate sampling but should be monitored for
    signs of respiratory disease

21
Guidelines for surveillance
  • Pigs vs humans (or viceversa)
  • From farms categorized as C1 collect 20 samples
    from each observation unit with on-going clinical
    cases
  • Should the overall number of pigs be less than 20
    samples should be collected from all of them.

22
Guidelines for surveillance
  • Pigs vs humans (or viceversa)
  • From farms categorized as C2 the sample size
    should be increased according to the criteria of
    being able to detect at least 1 case at 1
    prevalence and 95 confidence level.

23
Guidelines for surveillance
  • Pigs vs humans (or viceversa)
  • For pig farms falling in category C3 (and
    consequently not eligible for immediate sampling)
    a monitoring period should be initiated
  • The starting date (time 0) for the follow-up will
    be the date of the visit, the end of the
    follow-up period will be the date of the visit
    14 days. During this period the pig farm should
    ideally be visited at least twice (i.e. weekly)
    to verify that there are no signs of respiratory
    disease developing
  • Should cases of disease be detected consistent
    with the case definition used, the farm will be
    sampled according to the procedures already
    established in this document for category C1.

24
Guidelines for surveillance
  • Surveillance in pigs
  • Targeted or active surveillance of pigs could be
    considered at slaughterhouses, abattoirs, and in
    some countries animal markets
  • Surveillance should be based in animals showing
    clinical respiratory signs (the assumption is
    that health events matching the case definition
    are reported to veterinary authorities)

25
Guidelines for surveillance
  • Surveillance in pigs
  • Should occurrence of those cases being reported
    the farm should fall into category C1 and
    consequently sampling criteria should follow the
    same adopted in farms with on-going cases
  • Up to 20 animals sampled for each observation
    unit
  • Where clinical cases exceed 20 animals, all
    samples collected from clinical cases
  • If fewer clinical cases, in-contact animals will
    also be sampled

26
Guidelines for surveillance
  • Surveillance in pigs (to prove absence)
  • No official international requirements exist for
    recognition of countries, zones, compartments or
    individual farms as free from classical swine
    influenza viruses or from the Pandemic H1N1/2009
    virus
  • Reference to the guidelines in Chapter 1.4.1 of
    the OIE Terrestrial Animal Health Code are
    recommended

27
Guidelines for surveillance
  • Surveillance in pigs (to prove absence)
  • Target population
  • All pig farms in a country, zone or compartment.
    Pigs in slaughterhouses or markets also can be
    included.
  • - Sampling criteria
  • e.g. multistage random surveys adequate to detect
    at least 1 of prevalence if the virus is
    circulating with a 99 confidence

28
New challenges
  • The One-World-One-Health approach recognizes the
    intimate linkages among the human, animal and
    ecosystem health domains (which appears to be the
    most appropriate for addressing issues such as
    Influenza A/H1N1 and more in general the issue of
    Influenza viruses)
  • It proposes an international, interdisciplinary,
    cross-sectoral approach to disease surveillance,
    monitoring, prevention, control and mitigation of
    emerging diseases, as well as to environmental
    conservation.

29
New challenges
  • The major lesson learned (from the Highly
    Pathogenic Avian Influenza H5N1 but can be
    extended to other diseases) is the central
    importance of efficient surveillance, effective
    inter-sectoral collaboration, a well-designed
    national strategy and sustained political will.

30
New challenges
  • Where any of these elements has been absent or
    insufficient, countries have been less able to
    detect and control the spread of infection such
    as HPAI H5N1, with the result that in some
    countries the disease has become entrenched in
    poultry and thereby increasing the possibility of
    human infection.

31
New challenges
  • Should swine influenza be included among the list
    of notifiable diseases?
  • What should be done if detected in pigs?
  • Should the surveillance system for influenza
    viruses be seen as a multi-component system
    incorporating different animal species (including
    humans) under a single framework?
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