CategoryPublic Health - Influenza
Date Full Report Received07/01/2017
Date Abstract Report Received07/01/2017
Funded ByNational Pork Board
Pigs play a critical role in the ecology and epidemiology of influenza A viruses (IAVs) by serving as a source of novel reassortant viruses infecting humans. Agricultural fairs and livestock exhibitions create an environment conducive to zoonotic IAV transmission by commingling pigs and people for a prolonged period, resulting in a dramatic increase in the number of documented variant influenza A cases in people during 2011-2016. The epidemiological investigations into the 306 reported human cases of variant H3N2 influenza A (H3N2v) that occurred in 2012 linked the majority of them to human-swine exposure occurring at fairs. Research conducted by this study team provided molecular confirmation of zoonotic H3N2v transmission at county fairs in addition to evidence that IAV infections are common among apparently healthy swine at agricultural fairs.
H3N2v outbreaks in 2011-2016 show that swine infected with IAV at fairs and livestock exhibitions are a public health threat. Reducing zoonotic transmission of IAV between pigs and people is crucial to both agriculture and public health. Swine industry leaders and public health officials are seeking strategies to reduce intra- and inter- species transmission of IAV at swine exhibitions. The ultimate objective of this proposal is to provide new knowledge and insight into the dynamics of IAVs circulating in exhibition swine that can be used to make evidence based recommendations to prevent cases, outbreaks, epidemics, and/or pandemics caused by swine-to-human transmission of IAV occurring at agricultural fairs and livestock exhibitions. In order to achieve this objective, three specific aims were investigated:
The scientific community currently had little data about IAV activity among exhibition swine at jackpot shows. While it is common to find > 75% of the pigs infected at agricultural fairs with IAV, we believed that jackpot shows, due to the short exhibition period (1-2 days), would not provide enough time for IAV amplification within the swine population as occurs at longer agricultural fairs (3-10 days). Therefore, we hypothesized that the prevalence of IAV at jackpot shows would be <5%. Animal and public health officials have recommended that swine exhibitions be shortened to less than 72 hours to limit influenza amplification. By sampling pigs at short duration jackpot shows, this aim will directly provide data to evaluate the recommendation of shortening swine exhibitions.
Our previous work has demonstrated that it is common to find similar IAVs at several fairs across a large geographic area (across states). We suspected that pigs were becoming infected with IAV at jackpot shows, subsequently start shedding virus after the show thus perpetuating viral transmission between additional naïve exhibition swine at future jackpot shows and local agricultural fairs. Thus, we hypothesized the IAV strains found in pigs at jackpot shows would be genomically the same as those strains found in pigs at agricultural fairs during the same year.
Pigs can be transported long distances for the purpose of competition in livestock shows, which may facilitate rapid and wide-spread dissemination of IAV. The extent to which exhibition pigs move for competition has been poorly defined but may be a critical key in understanding the natural history of IAV in exhibition swine. We sought to better define the extent of swine movement for the purposes of exhibition by capturing the zip code of residence of jackpot show exhibitors.