Active Influenza A Virus Surveillance in Swine at Agricultural Fairs

Pigs are recognized to play a key role in the ecology and epidemiology of influenza A virus infections and in the emergence of novel viruses which may progress to pandemics. Retrospective epidemiological investigations have demonstrated multi-directional interspecies transmission of influenza A viruses can occur between humans and swine at agricultural fairs. Following the emergence of the influenza A(H1N1)pdm09 virus, we hypothesized that an active, influenza A virus surveillance program at agriculture exhibitions could be used as an active, cost-effective, and efficient, approach for the early detection of zoonotic transmission of influenza A virus between swine and humans.;The second chapter of this dissertation describes the results of a study investigating the effectiveness of two virus isolation methods for the recovery of contemporary influenza A virus strains circulating in swine at agricultural exhibitions. Results demonstrated MDCK cells adapted to serum free medium were better than embryonating chicken eggs for the recovery of contemporary swine-origin influenza A viruses circulating in swine at agriculture exhibits.;The third chapter examines influenza A virus activity at selected agricultural fairs in Ohio over three years, 2009-2011. The results demonstrated that subclinical influenza A virus infections were common among exhibition swine in Ohio and these infections were going unreported in current national swine influenza virus surveillance programs. These subclinical infections at the swine-human interface were hypothesized to be playing a role in variant influenza A virus infections in humans.;The fourth chapter expanded upon the previous chapters to conduct active virus surveillance at Ohio agriculture exhibitions during 2012. This study used nucleotide sequencing of isolates concurrently recovered from humans and pigs at the same location to confirm that H3N2pM influenza A virus infections in pigs were the source of H3N2v influenza A viruses infecting humans.;In chapter five, further analyses of isolates from pigs and humans from across Ohio during 2012 provided evidence that interspecies transmission was not limited to one rare event but the occurred at six additional agriculture exhibits over a three week period. Nucleotide identity of the H3N2 isolates from humans and swine at all seven fairs was greater than 99%, indicating that this H3N2pM swine-origin influenza A virus became widely disseminated among exhibition swine across Ohio during the 2012 fair season and was transmitted to humans at each of the seven fairs.;In chapter six, the final study seeked to examine fair-level risk factors potentially contributing to influenza A virus infections in the pigs at agricultural fairs. These data collected during 2012 indicate that larger swine shows have an increased risk for the presence of influenza A virus among the swine at the exhibition.;Overall, this project has established an active surveillance program to study influenza A virus activity at the swine-human interface. The first three years of the program provide an invaluable set of baseline data to which future results can be compared. The outcomes documented in 2012 highlight the need for effective mitigation strategies to control intra- and inter-species spread of influenza A virus at swine exhibitions.