Pandemic H1N12009 Influenza in Pigs

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Pandemic H1N1/2009 Influenza in Pigs

• Renita W. Marshall, DVM, MS
• Southern University System
• Southern University Agricultural Research
  Extension Center
• EDEN Webinar

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What is Swine Influenza?

• Respiratory disease of pigs
• Influenza A viruses
• H1N1
• H1N2
• H3N2
• Isolated from a pig in 1930
• Common in North and South America, Europe, Asia,
  Africa

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What is Swine Influenza?

• From 1930 to the late 1990s these classical swine
  influenza viruses circulated in pigs in the US
  and remained relatively stable.

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Classical Swine Flu

• High levels of illness
• Low death rates
• Outbreaks during late fall and winter months
• Morbidity rapidly reaches 100
• Mortality usually does not exceed 1
• Recovery usually after 5-7 days

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Disease Surveillance

• Disease surveillance is a tool for action
• Many countries in the world do not have
  sufficient capacity in place
• Many do not consider swine influenza virus
  infections as a high priority

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Disease Surveillance

• There are currently no guidelines or set of
  defined strategies to address this disease
• Industrial pig farms around the world apply
  vaccinations to control clinical disease
• Although swine influenza is not a notifiable
  disease, all exceptional events related to
  Pandemic H1N1/2009 virus in swine should be
  reported

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Disease Surveillance

• The adaptation of surveillance schemes is
  encouraged.
• Surveillance should include the active
  participation of local communities and farmers to
  report active respiratory cases in pigs.

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Recognizing the signs of flu in pigs

• sudden onset of fever
• lethargy, lack of alertness
• going off feed (poor appetite)
• coughing (barking)
• discharge from the nose or eyes, eye redness or
  inflammation
• sneezing
• breathing difficulties

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If swine influenza is identified.

• FAO recommends that animals be given supportive
  care and allowed to recover
• Culling of affected swine is not recommended
• Animal handlers should protect themselves from
  potential zoonotic agents

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If swine influenza is identified.

• Animal handlers should seek early medical
  attention if they become ill
• Feverish
• Respiratory or other symptoms
• Pig workers with symptoms of flu should not work
  on pig farms

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Serological Testing

• Serology for H1N1 should not be used as the sole
  indicator of previous infection with the Pandemic
  H1N1/2009 influenza virus
• Current tests do not differentiate between H1N1
  strains
• Influenza viruses of H1N1 sub-type are common
  among pig populations

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Serological Testing

• Vaccinations against swine influenza is based on
  inactivated H1N1 vaccines.
• Serology may be useful where swine influenza
  vaccination is not practiced
• Serology may be used in conjunction with other
  testing methods to confirm the presence of the
  virus

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Virological Assays

• Currently preferred over serology
• Virus isolation techniques are the most sensitive
  and specific for detection of Pandemic H1N1/2009
  influenza viruses in pigs
• As of July 2009 there was no standardized
  veterinary laboratory protocol available.

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Molecular Sequencing

• Molecular sequencing of the HA gene is currently
  the most definitive confirmation of the Pandemic
  H1N1/2009 influenza virus.
• Consultation with an influenza reference
  laboratory is strongly recommended.

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Criteria to establish a surveillance program

• Surveillance for the Pandemic H1N1/2009 virus is
  aimed to answer one of three questions
• Are swine the source of human exposure?
• Can we demonstrate absence of the Pandemic
  H1N1/2009 virus in pigs?
• Is the Pandemic H1N1/2009 virus being detected
  and collected from
  swine populations?

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Case Definition

• 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.

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Are swine the possible sources of human cases of
Pandemic H1N1/2009 influenza virus?

• Having consumed pork products is not to be
  considered as a risk factor for influenza but
  only contact with live animals.
• A window period of exposure for the persons
  affected should be identified.
• Occupational (daily contact with pigs) and
  non-occupational exposure such as visiting farms,
  petting zoos, and livestock shows should be
  considered.

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Are swine the possible sources of human cases of
Pandemic H1N1/2009 influenza virus?

• Preliminary info may lead to identification of
  one or more pig farms where investigation is
  required.
• Confirmation that pigs were the source of
  infection might be supported by virus comparison
  between pig and human viruses.

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Can we demonstrate absence of the Pandemic
H1N1/2009 virus in pigs?

• There are no official international requirements
  for, nor recognition of countries, zones,
  compartments or individual farms as free from
  classical swine viruses or from the Pandemic
  H1N1/2009 virus.

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General Surveillance Strategy

• Targets
• Slaughterhouses
• Abattoirs
• Animal markets
• Sampling criteria
• Screening
• No more than 20 animals (nasal swabs) unless
  clinically affected

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Risk Management of Influenza Viruses in Swine
Populations
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Outbreak investigation protocols

• Laboratory sampling procedures
• Developed and disseminated
• Veterinary professionals
• Animal health workers

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Regular surveillance

• Should be intensified (porcine respiratory
  diseases)
• Cases should be investigated by national
  veterinary authorities.
• If Pandemic H1N1/2009 is suspected
• Confirmation using molecular sequencing
  techniques
• If Pandemic H1N1/2009 is confirmed
• OIE and FAO should be informed

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Movement restrictions

• Should be implemented by farms and holdings with
  confirmed cases of Pandemic H1N1/2009 influenza
  virus
• Should be in force until 1 week to 10 days after
  the last animal has recovered
• Overcrowding
• Slaughter (clinically healthy)

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Movement restrictions

• No need to cull affected animals
• Separate from healthy herd-mates
• Allowed to recover
• In case of suspected outbreak, movement
  restrictions should be in place until a
  laboratory diagnosis is available.

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Biosecurity and Personal Protection

• Animal handlers and veterinarians should wear
  protective gear
• When entering barns or areas where sick pigs are
  present
• Disposable coveralls or barn clothes
• Shoes or boots that can be disinfected
• Barn clothes should ideally be laundered at the
  barn

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Biosecurity and Personal Protection

• Minimize the risk of spreading pathogens between
  pigs and locations
• Proper cleaning and disinfection
• quaternary ammonium compounds
• 10 bleach solutions
• Workers should not be allowed to visit or work at
  other sites.

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Biosecurity and Personal Protection

• Persons working directly with swine should be
  urged not to go to work if they have any signs of
  respiratory disease, fever or any influenza-like
  illness
• Biosecurity should be increased in pig herds to
  prevent transmission
• Fomites
• Mechanical vectors
• vehicles

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Vaccination for Swine Influenza

• A vaccine could be used in swine
• High risk areas
• Considered effective against the circulation
  strain
• Permitted by the relevant authorities

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Closing.

• Classical swine influenza is prevalent in pigs
  worldwide.
• H1N1 and H3N2 swine viruses are endemic among pig
  populations in the US and something that the
  industry deals with routinely.
• In the U.S., studies have shown that 30 percent
  of the pig population has antibody evidence of
  having had H1N1 infection.
• More specifically, 51 percent of pigs in the
  north-central U.S. have been shown to have
  antibody evidence of infection with swine H1N1.

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Closing.

• As of June 26, 2009, the novel influenza A (H1N1)
  virus has not been found in any pigs within the
  United States, but has been detected in pigs on a
  farm in Alberta, Canada.
• Information sharing between countries of the
  results of surveillance activities for classical
  swine influenza, the emergent Pandemic H1N1/2009
  influenza virus, and other novel viruses would
  improve the overall understanding of influenza
  dynamics and the different types of pig
  production systems where they circulate.

Key Facts about Swine Influenza (Swine Flu),
Center for Disease Control