Subclinical Influenza Virus A Infections in Pigs Exhibited at Agricultural Fairs, Ohio, USA, 2009–2011

Bowman, Andrew S.; Nolting, Jacqueline M.; Nelson, Sarah W.; Slemons, Richard D.

doi:10.3201/eid1812.121116

Cited by 60 publications

(82 citation statements)

References 30 publications

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“…In 2011, the majority of sampled pigs were reported as “healthy” and similar levels of detection were observed in “healthy” and sick animals. The relatively high number of positive “healthy” animals observed may be partly explained by the occurrence of subclinical infections 33. However, the information collected on health status may be biased by the ability of the collector to observe respiratory signs at the time of sampling.…”

Section: Discussionmentioning

confidence: 99%

Origin, distribution, and potential risk factors associated with influenza A virus in swine in two production systems in Guatemala

Gonzalez‐Reiche

Ramírez

Müller

et al. 2017

Influenza Resp Viruses

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BackgroundGuatemala is the country with the largest swine production in Central America; however, evidence of influenza A virus (IAV) in pigs has not been clearly delineated.ObjectivesIn this study, we analyzed the presence and spatial distribution of IAV in commercial and backyard swine populations.MethodsSamples from two nationwide surveys conducted in 2010 and 2011 were tested using virological (rRT‐PCR and virus isolation) and serological (ELISA and hemagglutination inhibition) assays to detect IAV.ResultsInfluenza A virus was detected in 15.7% of the sampled pigs (30.6% of herds) in 2010 and in 11.7% (24.2% of herds) in 2011. The percentage of seropositive pigs was 10.6% (16.1% of herds) and 1.4% (3.1% of herds) for each year, respectively. Three pandemic H1N1 and one seasonal human‐like H3N2 viruses were isolated. Antibodies against viruses from different genetic clusters were detected. No reassortant strains with swine viruses were detected. The H3N2 virus was closely related to human viruses that circulated in Central America in 2010, distinct to the most recent human seasonal vaccine lineages. Spatial clusters of rRT‐PCR positive herds were detected each year by scan statistics.ConclusionsOur results demonstrate circulation of IAV throughout Guatemala and identify commercial farms, animal health status, and age as potential risk factors associated with IAV infection and exposure. Detection of human‐origin viruses in pigs suggests a role for humans in the molecular epidemiology of IAV in swine in Guatemala and evidences gaps in local animal and human surveillance.

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Section: Discussionmentioning

confidence: 99%

Origin, distribution, and potential risk factors associated with influenza A virus in swine in two production systems in Guatemala

Gonzalez‐Reiche

Ramírez

Müller

et al. 2017

Influenza Resp Viruses

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“…Agricultural fairs are one such venue where pigs and people from multiple sources and locations concentrate in relatively close proximity, and combined with the propensity for prolonged exposure, this may facilitate interspecies transmission. The transmission of IAV is bidirectional, with several reported human-to-swine and swine-to-human transmission events associated with agricultural fairs (11,27). In the fall of 2011, there were a limited number of reports of human IAV infection with a swine origin H3N2 virus, all of which were epidemiologically linked to exposure to pigs at county fairs.…”

Section: Discussionmentioning

confidence: 99%

Efficacy in Pigs of Inactivated and Live Attenuated Influenza Virus Vaccines against Infection and Transmission of an Emerging H3N2 Similar to the 2011-2012 H3N2v

Loving

Lager

Vincent

et al. 2013

J Virol

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cVaccines provide a primary means to limit disease but may not be effective at blocking infection and pathogen transmission. The objective of the present study was to evaluate the efficacy of commercial inactivated swine influenza A virus (IAV) vaccines and experimental live attenuated influenza virus (LAIV) vaccines against infection with H3N2 virus and subsequent indirect transmission to naive pigs. The H3N2 virus evaluated was similar to the H3N2v detected in humans during 2011-2012, which was associated with swine contact at agricultural fairs. One commercial vaccine provided partial protection measured by reduced nasal shedding; however, indirect contacts became infected, indicating that the reduction in nasal shedding did not prevent aerosol transmission. One LAIV vaccine provided complete protection, and none of the indirect-contact pigs became infected. Clinical disease was not observed in any group, including nonvaccinated animals, a consistent observation in pigs infected with contemporary reassortant H3N2 swine viruses. Serum hemagglutination inhibition antibody titers against the challenge virus were not predictive of efficacy; titers following vaccination with a LAIV that provided sterilizing immunity were below the level considered protective, yet titers in a commercial vaccine group that was not protected were above that level. While vaccination with currently approved commercial inactivated products did not fully prevent transmission, certain vaccines may provide a benefit by limitating shedding, transmission, and zoonotic spillover of antigenically similar H3N2 viruses at agriculture fairs when administered appropriately and used in conjunction with additional control measures.

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“…Perform quality assurance testing on the viral transport medium by testing for influenza A virus matrix protein by rRT-PCR, as described by Zhang and Harmon. 22 7. Dispense 5 ml of the viral transport medium into sterile high-density polyethylene bottles with 8 ml capacity.…”

Section: Preparation Of Viral Transport Medium and Sample Collection mentioning

confidence: 99%

“…15 Genomic analysis of viral isolates from exhibition pigs compared with human isolates confirmed zoonotic transmission. 21 Exhibition swine infected with IAV often do not show clinical signs of illness, [21][22][23] indicating the need for direct diagnostic tests.…”

Section: Introductionmentioning

confidence: 99%

Nasal Wipes for Influenza A Virus Detection and Isolation from Swine

Nolting

Szablewski

Edwards

et al. 2015

JoVE

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Surveillance for influenza A viruses in swine is critical to human and animal health because influenza A virus rapidly evolves in swine populations and new strains are continually emerging. Swine are able to be infected by diverse lineages of influenza A virus making them important hosts for the emergence and maintenance of novel influenza A virus strains. Sampling pigs in diverse settings such as commercial swine farms, agricultural fairs, and live animal markets is important to provide a comprehensive view of currently circulating IAV strains. The current goldstandard ante-mortem sampling technique (i.e. collection of nasal swabs) is labor intensive because it requires physical restraint of the pigs. Nasal wipes involve rubbing a piece of fabric across the snout of the pig with minimal to no restraint of the animal. The nasal wipe procedure is simple to perform and does not require personnel with professional veterinary or animal handling training. While slightly less sensitive than nasal swabs, virus detection and isolation rates are adequate to make nasal wipes a viable alternative for sampling individual pigs when low stress sampling methods are required. The proceeding protocol outlines the steps needed to collect a viable nasal wipe from an individual pig. Video LinkThe video component of this article can be found at

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Subclinical Influenza Virus A Infections in Pigs Exhibited at Agricultural Fairs, Ohio, USA, 2009–2011

Abstract: Close contact between pigs and humans could result in zoonotic transmission.

Cited by 60 publications

References 30 publications

Origin, distribution, and potential risk factors associated with influenza A virus in swine in two production systems in Guatemala

Origin, distribution, and potential risk factors associated with influenza A virus in swine in two production systems in Guatemala

Efficacy in Pigs of Inactivated and Live Attenuated Influenza Virus Vaccines against Infection and Transmission of an Emerging H3N2 Similar to the 2011-2012 H3N2v

Nasal Wipes for Influenza A Virus Detection and Isolation from Swine

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