The story of swine influenza in Sri Lanka

Abstract

Influenza A virus infections in pigs is a disease of concern in terms of both animal and human health. Systematic virological and serological surveillance was carried in the Government Slaughter House Dematagoda, Sri Lanka during 2009-2013, with paired nasal and tracheal swabs from 4683 animals and serum from 3351 animals. We isolated 26 H1N1pdm like virus from swine swabs from MDCK monolayers and serological data was obtained by haemagglutination inhibition test using panel of swine and human viral antigens. We comprehensively analyzed full genomes of viral isolates from 26 swine and 35 human samples. To understand the molecular epidemiology and spatial and temporal dynamics of spillover events, we compared our data with full-genome sequences of H1N1pdm available in public databases as of August 2013. Full genome phylogenetic and epidemiologic analysis of the human and swine influenza viruses demonstrated natural independent spillover events of H1N1pdm influenza viruses from human to pigs, with self-limited transmission and extinction within pig herds. H1N1pdm viruses appear assembled as multiple discrete introductions into swine, followed by clonal expansion within swine. The spread of such virus lineages across multiple farms appears to be mediated by breaches of external bio-security measures including the manner of swine transportation.