Influenza Herd-Level Prevalence and Seasonality in Breed-to-Wean Pig Farms in the Midwestern United States
Chamba Pardo, Fabian Orlando (University of Minnesota. Veterinary Population Medicine Department)
Alba-Casals, Ana (University of Minnesota. Veterinary Population Medicine Department)
Nerem, Joel (Pipestone Veterinary Services)
Morrison, Robert B. (University of Minnesota. Veterinary Population Medicine Department)
Puig, Pedro (Universitat Autònoma de Barcelona. Departament de Matemàtiques)
Torremorell, Montserrat (University of Minnesota. Veterinary Population Medicine Department)

Data:	2017
Resum:	Influenza is a costly disease for pig producers and understanding its epidemiology is critical to control it. In this study, we aimed to estimate the herd-level prevalence and seasonality of influenza in breed-to-wean pig farms, evaluate the correlation between influenza herd-level prevalence and meteorological conditions, and characterize influenza genetic diversity over time. A cohort of 34 breed-to-wean farms with monthly influenza status obtained over a 5-year period in piglets prior to wean was selected. A farm was considered positive in a given month if at least one oral fluid tested influenza positive by reverse transcriptase polymerase chain reaction. Influenza seasonality was assessed combining autoregressive integrated moving average (ARIMA) models with trigonometric functions as covariates. Meteorological conditions were gathered from local land-based weather stations, monthly aggregated and correlated with influenza herd-level prevalence. Influenza herd-level prevalence had a median of 28% with a range from 7 to 57% and followed a cyclical pattern with levels increasing during fall, peaking in both early winter (December) and late spring (May), and decreasing in summer. Influenza herd-level prevalence was correlated with mean outdoor air absolute humidity (AH) and temperature. Influenza genetic diversity was substantial over time with influenza isolates belonging to 10 distinct clades from which H1 delta 1 and H1 gamma 1 were the most common. Twenty-one percent of farms had three different clades co-circulating over time, 18% of farms had two clades, and 41% of farms had one clade. In summary, our study showed that influenza had a cyclical pattern explained in part by air AH and temperature changes over time, and highlighted the importance of active surveillance to identify high-risk periods when strategic control measures for influenza could be implemented.
Drets:	Aquest document està subjecte a una llicència d'ús Creative Commons. Es permet la reproducció total o parcial, la distribució, la comunicació pública de l'obra i la creació d'obres derivades, fins i tot amb finalitats comercials, sempre i quan es reconegui l'autoria de l'obra original.
Llengua:	Anglès
Document:	Article ; recerca ; Versió publicada
Matèria:	Influenza ; Seasonality ; Prevalence ; Genetic diversity ; Swine ; Absolute humidity ; Breed-to-wean pig farm ; Swine influenza virus
Publicat a:	Frontiers in Veterinary Science, Vol. 4 (October 2017) , art. 167, ISSN 2297-1769

DOI: 10.3389/fvets.2017.00167
PMID: 29075636

10 p, 3.3 MB

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