title: Efficient isolation of Swine influenza viruses by age-targeted specimen collection.
abstract: The control of swine influenza virus (SIV) infection is paramount for increasing the productivity of pig farming and minimizing the threat of pandemic outbreaks. Thus, SIV surveillance should be conducted by region and on a regular basis. Here, we established a microneutralization assay specific for SIV seroprevalence surveillance by using reporter gene-expressing recombinant influenza viruses. Growth-based SIV seroprevalence revealed that most sows and piglets were positive for neutralizing antibodies against influenza viruses. In contrast, the 90-day-old growing pigs exhibited limited neutralizing activity in their sera, suggesting that this particular age of population is most susceptible to SIV infection and thus is an ideal age group for SIV isolation. From nasal swab specimens of healthy pigs in this age population, we were able to isolate SIVs at a higher incidence (5.3%) than those of previous reports. Nucleotide sequencing and phylogenetic analysis of the hemagglutinin (HA) genes revealed that the isolated SIVs have circulated and evolved in pigs but not have been recently introduced from humans, implying that a large number of SIV lineages may remain "undiscovered" in the global porcine populations. We propose that the 90-day-old growing pig-targeted nasal swab collection presented in this study facilitates global SIV surveillance and contributes to the detection and control of SIV infection.
authors.affiliation: Laboratory of Animal Hygiene, Joint Faculty of Veterinary Medicine, Kagoshima University, Kagoshima, Japan Transboundary Animal Diseases Center, Joint Faculty of Veterinary Medicine, Kagoshima University, Kagoshima, Japan United Graduate School of Veterinary Science, Yamaguchi University, Yamaguchi, Japan mozawa@vet.kagoshima-u.ac.jp.
authors.forename: Makoto
authors.initials: M
authors.lastname: Ozawa
authors.affiliation: Transboundary Animal Diseases Center, Joint Faculty of Veterinary Medicine, Kagoshima University, Kagoshima, Japan United Graduate School of Veterinary Science, Yamaguchi University, Yamaguchi, Japan.
authors.forename: Aya
authors.initials: A
authors.lastname: Matsuu
authors.affiliation: Department of Computer Bioscience, Nagahama Institute of Bio-Science and Technology, Nagahama, Japan.
authors.forename: Kouki
authors.initials: K
authors.lastname: Yonezawa
authors.affiliation: Hokkaido University Research Center for Zoonosis Control, Sapporo, Japan Global Institution for Collaborative Research and Education, Hokkaido University, Sapporo, Japan.
authors.forename: Manabu
authors.initials: M
authors.lastname: Igarashi
authors.affiliation: Laboratory of Animal Hygiene, Joint Faculty of Veterinary Medicine, Kagoshima University, Kagoshima, Japan.
authors.forename: Kosuke
authors.initials: K
authors.lastname: Okuya
authors.affiliation: Transboundary Animal Diseases Center, Joint Faculty of Veterinary Medicine, Kagoshima University, Kagoshima, Japan.
authors.forename: Toshiko
authors.initials: T
authors.lastname: Kawabata
authors.affiliation: Hokkaido University Research Center for Zoonosis Control, Sapporo, Japan Global Institution for Collaborative Research and Education, Hokkaido University, Sapporo, Japan.
authors.forename: Kimihito
authors.initials: K
authors.lastname: Ito
authors.affiliation: Laboratory of Animal Hygiene, Joint Faculty of Veterinary Medicine, Kagoshima University, Kagoshima, Japan Transboundary Animal Diseases Center, Joint Faculty of Veterinary Medicine, Kagoshima University, Kagoshima, Japan United Graduate School of Veterinary Science, Yamaguchi University, Yamaguchi, Japan.
authors.forename: Kyoko
authors.initials: K
authors.lastname: Tsukiyama-Kohara
authors.affiliation: Vaxxinova Japan K.K., Tokyo, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Taneno
authors.affiliation: Transboundary Animal Diseases Center, Joint Faculty of Veterinary Medicine, Kagoshima University, Kagoshima, Japan United Graduate School of Veterinary Science, Yamaguchi University, Yamaguchi, Japan Laboratory of Farm Animal Production Medicine, Joint Faculty of Veterinary Medicine, Kagoshima University, Kagoshima, Japan.
authors.forename: Eisaburo
authors.initials: E
authors.lastname: Deguchi
mesh_terms: D000367:Age Factors; D000818:Animals; D062665:Epidemiological Monitoring; D005838:Genotype; D019267:Hemagglutinin Glycoproteins, Influenza Virus / Q000235:genetics; D006801:Humans; D008969:Molecular Sequence Data; D009296:Nasal Cavity / Q000821:virology; D009500:Neutralization Tests / Q000379:methods*; D009975:Orthomyxoviridae / Q000276:immunology / Q000302:isolation & purification*; D009976:Orthomyxoviridae Infections / Q000175:diagnosis* / Q000453:epidemiology*; D010802:Phylogeny; D017422:Sequence Analysis, DNA; D017385:Sequence Homology; D016036:Seroepidemiologic Studies; D013048:Specimen Handling / Q000379:methods*; D013552:Swine; D013553:Swine Diseases / Q000175:diagnosis* / Q000453:epidemiology*
chemical_list: D019267:Hemagglutinin Glycoproteins, Influenza Virus