High turnover drives prolonged persistence of influenza in managed pig herds

Virginia E. Pitzer*, Ricardo Aguas, Steven Riley, Willie L.A. Loeffen, James L.N. Wood, Bryan T. Grenfell

*Corresponding author for this work

Research output: Contribution to journalArticleAcademicpeer-review

14 Citations (Scopus)

Abstract

Pigs have long been hypothesized to play a central role in the emergence of novel human influenza A virus (IAV) strains, by serving as mixing vessels for mammalian and avian variants. However, the key issue of viral persistence in swine populations at different scales is ill understood. We address this gap using epidemiological models calibrated against seroprevalence data from Dutch finishing pigs to estimate the 'critical herd size' (CHS) for IAV persistence. We then examine the viral phylogenetic evidence for persistence by comparing human and swine IAV. Models suggest a CHS of approximately 3000 pigs above which influenza was likely to persist, i.e. orders of magnitude lower than persistence thresholds for IAV and other acute viruses in humans. At national and regional scales, we found much stronger empirical signatures of prolonged persistence of IAV in swine compared with human populations. These striking levels of persistence in small populations are driven by the high recruitment rate of susceptible piglets, and have significant implications for management of swine and for overall patterns of genetic diversity of IAV.

Original languageEnglish
Article number20160138
JournalJournal of the Royal Society, Interface
Volume13
Issue number119
DOIs
Publication statusPublished - 2016

Fingerprint

Viruses
Influenza A virus
Human Influenza
Swine
Population
Seroepidemiologic Studies

Keywords

  • Influenza
  • Mathematical modelling
  • Surveillance
  • Swine
  • Transmission dynamics

Cite this

Pitzer, Virginia E. ; Aguas, Ricardo ; Riley, Steven ; Loeffen, Willie L.A. ; Wood, James L.N. ; Grenfell, Bryan T. / High turnover drives prolonged persistence of influenza in managed pig herds. In: Journal of the Royal Society, Interface. 2016 ; Vol. 13, No. 119.
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High turnover drives prolonged persistence of influenza in managed pig herds. / Pitzer, Virginia E.; Aguas, Ricardo; Riley, Steven; Loeffen, Willie L.A.; Wood, James L.N.; Grenfell, Bryan T.

In: Journal of the Royal Society, Interface, Vol. 13, No. 119, 20160138, 2016.

Research output: Contribution to journalArticleAcademicpeer-review

TY - JOUR

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AU - Pitzer, Virginia E.

AU - Aguas, Ricardo

AU - Riley, Steven

AU - Loeffen, Willie L.A.

AU - Wood, James L.N.

AU - Grenfell, Bryan T.

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AB - Pigs have long been hypothesized to play a central role in the emergence of novel human influenza A virus (IAV) strains, by serving as mixing vessels for mammalian and avian variants. However, the key issue of viral persistence in swine populations at different scales is ill understood. We address this gap using epidemiological models calibrated against seroprevalence data from Dutch finishing pigs to estimate the 'critical herd size' (CHS) for IAV persistence. We then examine the viral phylogenetic evidence for persistence by comparing human and swine IAV. Models suggest a CHS of approximately 3000 pigs above which influenza was likely to persist, i.e. orders of magnitude lower than persistence thresholds for IAV and other acute viruses in humans. At national and regional scales, we found much stronger empirical signatures of prolonged persistence of IAV in swine compared with human populations. These striking levels of persistence in small populations are driven by the high recruitment rate of susceptible piglets, and have significant implications for management of swine and for overall patterns of genetic diversity of IAV.

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