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Since the pandemic H1N1 emergence in 2009 (pdmH1N1), many reassortant pdmH1N1 viruses emerged and found circulating in the pig population worldwide. Currently, commercial human subunit vaccines are used commonly to prevent the influenza symptom based on the WHO recommendation. In case of current reassortant swine influenza viruses transmitting from pigs to humans, the efficacy of current human influenza vaccines is of interest. In this study, influenza A negative pigs were vaccinated with selected commercial human subunit vaccines and challenged with rH3N2. All sera were tested with both HI and SN assays using four representative viruses from the surveillance data in 2012 (enH1N1, pdmH1N1, rH1N2 and rH3N2). The results showed no significant differences in clinical signs and macroscopic and microscopic findings among groups. However, all pig sera from vaccinated groups had protective HI titers to the enH1N1, pdmH1N1 and rH1N2 at 21DPV onward and had protective SN titers only to pdmH1N1and rH1N2 at 21DPV onward. SN test results appeared more specific than those of HI tests. All tested sera had no cross-reactivity against the rH3N2. Both studied human subunit vaccines failed to protect and to stop viral shedding with no evidence of serological reaction against rH3N2. SIV surveillance is essential for monitoring a novel SIV emergence potentially for zoonosis., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

We studied the occurrence of swine influenza virus (SIV) infection in piglets with respiratory symptoms resembling porcine respiratory disease complex (PRDC). A total of 106 samples including nasal swab and lung suspension from sick piglets were collected from 30 farms of medium size in the central and eastern parts of Thailand from August 2006 to February 2007. Samples were inoculated onto Mardin-Darby Canine Kidney (MDCK) cells and SIV infection was confirmed by immunofluorescent assay (IFA) and reverse transcriptase polymerase chain reaction (RT-PCR) specific for M gene. Of 106 samples, 3 pigs from 3 different farms were found to be SIV positive on all assays. The positive samples were further identified by RT-PCR as H3N2 subtype using specific primers for hemagglutinin (HA) and neuraminidase (NA) genes. SIV infection was found in 2.8% of swine suffering from respiratory distress suggesting SIV may not be the major pathogen for PRDC in the central and eastern Thailand. SIV was present in 3 of 30 farms (10%) indicating the prevalence of SIV in these regions is considerable. Since pigs are vulnerable to infection from both human and avian influenza viruses and interspecies transmission between humans and swine occurs sporadically, it is essential to continue surveillance and monitoring of SIV infection in the swine population.