Southern University Agricultural Research and Extension Center
Pandemic H1N1/2009
Influenza in Pigs
Renita W. Marshall, DVM, MS
Southern University System
Southern University Agricultural Research & Extension Center
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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
•
•
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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 nonoccupational 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 northcentral 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
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