CategoryPublic Health - Influenza
Date Full Report Received10/13/2017
Date Abstract Report Received10/13/2017
Funded ByNational Pork Board
Influenza is an important respiratory disease of pigs, resulting in substantial economic burden to swine producers every year. Pigs were purported to be mixing vessels for influenza A viruses (IAV) due to their susceptibility to infection with IAV from different species and a potential role in generating novel reassorted viruses. This resulted in a biased view of pigs and swine agriculture as the main source of human pandemic viruses. Though there is the potential for swine viruses to be transmitted to humans, like the 2009 H1N1 pandemic, there is also evidence that human seasonal viruses frequently spillover into pigs and have a major impact in IAV diversity in swine. However, changes to the human viruses appear to be required for human-origin viruses to infect and subsequently become transmissible from pig to pig to be maintained in swine populations. In 2012, a new spillover of a human seasonal H3 IAV was recognized in the U.S. that most likely occurred in the winter of 2010-2011. This H3N1 swine virus had a mixture of swine and human IAV gene segments from at least 3 source viruses. To investigate the underlying factors that allowed this human to swine spillover, we generated viruses from a putative human H3N2 parental virus and the swine H3N1, and swapped surface genes, hemagglutinin (HA) and neuraminidase (NA), and other virus genes, in an attempt to recreate the virus detected in nature. Our results showed that although the HA was crucial for the infectivity in pigs and swine tissue, the adaptation of these novel H3 viruses to swine depended on multiple genes. The swine-adapted HA alone was not sufficient to confer the full growth potential seen for the field isolates. These findings provide important information about the requirements for a human virus to adapt in swine and can be used to monitor swine surveillance data for viruses that have adaptation signatures similar to these novel human-like viruses. Rapid identification allows pork producers and veterinarians to implement more effective control measures to avoid establishment of additional novel human viruses before they become fully adapted and widespread. By reducing the IAV burden in the swine population, the public health perception, consumer confidence, and trust by trade-partners may be improved, and, importantly, reduce the economic cost of IAV to producers and the swine industry.