Submitted to: American Veterinary Medical Association Abstract
Publication Type: Abstract Only
Publication Acceptance Date: May 1, 2013
Publication Date: N/A
Technical Abstract: Surveillance for influenza A viruses (IAV) circulating in pigs and other non-human mammals has been chronically underfunded and virtually nonexistent in many areas of the world. In March-April 2009, a novel pandemic H1N1 emerged and demonstrated in a very public forum the paucity of data on influenza viruses in swine. The gene constellation of the emerging virus was demonstrated to be a combination of genes from swine influenza A viruses (SIV) of North American and Eurasian lineages that had never before been identified in swine or other species. The emergent H1N1 quickly spread in the human population and the outbreak reached pandemic level 6 as declared by the World Health Organization on June 11, 2009. Although the 8 gene segments of the novel virus are similar to available sequences of corresponding genes from SIV from North America and Eurasia, no closely related ancestral IAV with this gene combination had been identified in North America or elsewhere in the world. Other than sporadic transmission to humans, swine influenza A viruses of the H1N1 subtype historically have been distinct from avian and other mammalian H1N1 influenza viruses in characteristics of host specificity, serologic cross-reactivity, and/or nucleotide sequence. The emergence of the 2009 pandemic H1N1 (pH1N1) virus brought a heightened awareness to the evolution and epidemiology of influenza A viruses in swine and presents a new era of challenges and opportunities for understanding and controlling influenza in pigs. SIV remains as one of the leading causes of viral pneumonia in swine and is a significant contributor to the porcine respiratory disease complex (PRDC). In addition to the primary disease caused by IAV, this virus is well documented to predispose pigs and many other host species to subsequent secondary bacterial pneumonia, the effects of which may last long after IAV can be detected. Due to the complicated nature of IAV evolution in all major host species, it is recognized that inactivated vaccines have become a suboptimal method to control IAV in all populations under all conditions. Likewise, there is no single inactivated IAV vaccine that fits all situations in the U.S. swine industry. In addition to partial protection often seen from inactivated IAV vaccines, recent studies have demonstrated the potential for enhancement of disease and pathologic changes in the lungs of pigs vaccinated with a virus that does not sufficiently neutralize against a subsequent challenge virus. These data suggest that non-neutralizing inactivated vaccine-induced antibodies contributed to the enhanced disease known as vaccine-associated enhanced respiratory disease (VAERD). This presentation will review the global situation for SIV and the need for improved surveillance and improved SIV vaccines.