Control of a Reassortant Pandemic 2009 H1N1 Influenza Virus Outbreak in an Intensive Swine Breeding Farm: Effect of Vaccination and Enhanced Farm Management Practices.

Influenza A viruses in swine cause considerable economic losses and raise concerns about their zoonotic potential. The current paucity of thorough empirical assessments of influenza A virus infection levels in swine herds under different control interventions hinders our understanding of their effectiveness. Between 2012 and 2013, recurrent outbreaks of respiratory disease caused by a reassortant pandemic 2009 H1N1 (H1N1pdm) virus were registered in a swine breeding farm in North-East Italy, providing the opportunity to assess an outbreak response plan based on vaccination and enhanced farm management. All sows/gilts were vaccinated with a H1N1pdm-specific vaccine, biosecurity was enhanced, weaning cycles were lengthened, and cross-fostering of piglets was banned. All tested piglets had maternally-derived antibodies at 30 days of age and were detectable in 5.3% of ~90 day-old piglets. There was a significant reduction in H1N1pdm RT-PCR detections after the intervention. Although our study could not fully determine the extent to which the observed trends in seropositivity or RT-PCR positivity among piglets were due to the intervention or to the natural course of the disease in the herd, we provided suggestive evidence that the applied measures were useful in controlling the outbreak, even without an all-in/all-out system, while keeping farm productivity at full.

Temporal insight into the natural generation of a new reassortant porcine influenza virus in a swine holding.

The influenza A virus (IAV) subtypes H1N1, H3N2 and H1N2 are the most prevalent subtypes in swine in Italy. Reassortant influenza A viruses subtypes in swine appeared in European pig population. In particular reassortant viruses carrying genome segment from the pandemic H1N1 (H1N1pdm) are reported in many European countries, including Italy. In a 1000 sows farrow-to feeder farm, in Northern Italy, we isolated 10 IAVs from recurrent episodes of respiratory disease in 45-70 days-old pigs from September 2012 to June 2013. The antigenic and genetic characterization of the swine IAV isolates showed the contemporary circulation of H1N1 avian-like and H1N1pdm strains in the first outbreak. The analysis of the viruses isolated subsequently showed the circulation of H1N1pdm IAV and then the establishment of a new previously undescribed H1N1 reassortant strain with a pandemic derived hemagglutinin gene and all the other seven segments of swine H1N1 avian-like lineage.

Full-Genome Sequence of a Reassortant H1N1 Swine Influenza Virus Isolated from Pigs in Italy.

In this study, the full-genome sequence of a novel reassortant H1N1 swine influenza virus (SIV) is reported. The isolate has a hemagglutinin (HA) gene of the pandemic H1N1 influenza virus, but it carries the seven genome segments of the avian-origin H1N1 SIV currently circulating in European pig farms.