Acute Influenza A virus outbreak in an enzootic infected sow herd: Impact on viral dynamics, genetic and antigenic variability and effect of maternally derived antibodies and vaccination

Autoři: Pia Ryt-Hansen aff001;  Anders Gorm Pedersen aff002;  Inge Larsen aff003;  Jesper Schak Krog aff001;  Charlotte Sonne Kristensen aff004;  Lars Erik Larsen aff001
Působiště autorů: National Veterinary Institute, Technical University of Denmark, Kongens Lyngby, Denmark aff001;  Department of Health Technology, Section for Bioinformatics, Technical University of Denmark, Kongens Lyngby, Denmark aff002;  University of Copenhagen, Dpt. of Veterinary and Animal Sciences, Frederiksberg C, Denmark aff003;  SEGES, Danish Pig Research Centre, Aarhus N, Denmark aff004
Vyšlo v časopise: PLoS ONE 14(11)
Kategorie: Research Article
doi: 10.1371/journal.pone.0224854


Influenza A virus (IAV) is a highly contagious pathogen in pigs. Swine IAV (swIAV) infection causes respiratory disease and is thereby a challenge for animal health, animal welfare and the production economy. In Europe, the most widespread strategy for controlling swIAV is implementation of sow vaccination programs, to secure delivery of protective maternally derived antibodies (MDAs) to the newborn piglets. In this study we report a unique case, where a persistently swIAV (A/sw/Denmark/P5U4/2016(H1N1)) infected herd experienced an acute outbreak with a new swIAV subtype (A/sw/Denmark/HB4280U1/2017(H1N2)) and subsequently decided to implement a mass sow vaccination program. Clinical registrations, nasal swabs and blood samples were collected from four different batches of pigs before and after vaccination. Virus isolation, sequencing of the virus strain and hemagglutinin inhibition (HI) tests were performed on samples collected before and during the outbreak and after implementation of mass sow vaccination. After implementation of the sow mass vaccination, the time of infection was delayed and the viral load significantly decreased. An increased number of pigs, however, tested positive at two consecutive sampling times indicating prolonged shedding. In addition, a significantly smaller proportion of the 10–12 weeks old pigs were seropositive by the end of the study, indicating an impaired induction of antibodies against swIAV in the presence of MDAs. Sequencing of the herd strains revealed major differences in the hemagglutinin gene of the strain isolated before- and during the acute outbreak despite that, the two strains belonged to the same HA lineage. The HI tests confirmed a limited degree of cross-reaction between the two strains. Furthermore, the sequencing results of the hemagglutinin gene obtained before and after implementation of mass sow vaccination revealed an increased substitution rate and an increase in positively selected sites in the globular head of the hemagglutinin after vaccination.

Klíčová slova:

Amino acid sequence analysis – Antibodies – DNA sequence analysis – Influenza A virus – Nucleotide sequencing – Swine – Vaccination and immunization – Vaccines


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2019 Číslo 11