Pandemic H1N1/2009 Influenza in Pigs

Southern University Agricultural Research and Extension Center

“Linking Citizens of Louisiana with Opportunities for Success”

Pandemic H1N1/2009 Influenza in Pigs

Renita W. Marshall, DVM, MSSouthern University System

Southern University Agricultural Research & Extension CenterEDEN Webinar



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



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

What is Swine Influenza?



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



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



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



• 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.

Disease Surveillance



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



• 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

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

If swine influenza is identified…….



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



• 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

Serological Testing



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.



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.



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?



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.



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.



• 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.

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



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.



General Surveillance Strategy• Targets

– Slaughterhouses– Abattoirs– Animal markets

• Sampling criteria– Screening– No more than 20 animals (nasal swabs)

unless clinically affected



Risk Management of Influenza Viruses in Swine Populations



Outbreak investigation protocols• Laboratory sampling procedures• Developed and disseminated

– Veterinary professionals– Animal health workers



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



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)



• 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.

Movement restrictions



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



• 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.




• 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




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



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.



• 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.

Closing……………….

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

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Pandemic H1N1/2009 Influenza in Pigs