Influenza B viruses in pigs, Taiwan.

Ching‐Ping Tsai,Hsiang‐Jung Tsai

doi:10.1111/irv.12588

Ching‐Ping Tsai, Hsiang‐Jung Tsai

Open Access

https://doi.org/10.1111/irv.12588

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Abstract

BackgroundInfluenza B viruses (IBVs) have never been isolated from natural‐infected pigs in clinical cases, although the susceptibility of domestic pigs to experimental IBV infections had been confirmed as well as IBV‐specific antibodies were detected from pigs under natural and experimental conditions.ObjectivesWe aimed to assess and investigate the activities for infection and circulation of IBVs in pigs.MethodsAnnual active surveys for influenza have been implemented on swine populations in Taiwan since July 1998. Nasal swabs, trachea, lungs, and blood from pigs were tested using virological and serological assays for influenza. Gene sequences of influenza viral isolates were determined and characterized. Preliminary sero‐epidemiological data for influenza virus were investigated.ResultsThree strains of IBV were isolated and identified from natural‐infected pigs in 2014. Genetic characterization revealed the highest identities (>99%) of molecular sequence with the contemporary IBVs belonged to the B/Brisbane/60/2008 genetic clade of Victoria lineage in the phylogenetic trees for all 8 genes. IBV‐specific antibodies were detected in 31 (0.2%; 95%CI: 0.1%‐0.2%) of 15 983 swine serum samples from 29 (2.8%; 95%CI: 1.9%‐3.9%) of 1039 farm visits under annual active surveys from 2007 through 2017. Seropositive cases have been found sparsely in 1‐5 of test prefectures every year except 2015 and 2017 as well as scattered loosely over 26 townships/districts of 11 prefectures in Taiwan cumulatively in 11 years.ConclusionsInfluenza B viruse infections from humans to pigs remained sporadic and accidental currently in Taiwan but might have paved potential avenues for newly emerging zoonotic influenza in the future.

Highlights

Influenza viruses had been classified into 4 genera (A, B, C and D) in the Orthomyxoviridae family.[1]
Influenza B viruses (IBVs) are classified into two antigenically distinct lineages, according to the phylogenetic relationship of the hemagglutinin (HA) gene: the Victoria lineage B/ Victoria/2/1987 and the Yamagata lineage B/Yamagata/16/1988.6,7 Since 2008, most B/Victoria/2/1987 lineage viruses have belonged to the B/Brisbane/60/2008 genetic clade based on the HA gene sequences.[8]
An experimental challenge study was performed in pigs using two representative IBVs: B/Yamagata/16/1988 and B/ Brisbane/60/2008.14 The susceptibility of domestic pigs to IBV infection in the US study supports and extends former observations made in the 1960s

Summary

Background

Influenza B viruses (IBVs) have never been isolated from natural- infected pigs in clinical cases, the susceptibility of domestic pigs to experimental IBV infections had been confirmed as well as IBV-specific antibodies were detected from pigs under natural and experimental conditions. Objectives: We aimed to assess and investigate the activities for infection and circulation of IBVs in pigs. Methods: Annual active surveys for influenza have been implemented on swine populations in Taiwan since July 1998. Gene sequences of influenza viral isolates were determined and characterized. IBV-specific antibodies were detected in 31 (0.2%; 95%CI: 0.1%-0.2%) of 15 983 swine serum samples from 29 (2.8%; 95%CI: 1.9%-3.9%) of 1039 farm visits under annual active surveys from 2007 through 2017. Conclusions: Influenza B viruse infections from humans to pigs remained sporadic and accidental currently in Taiwan but might have paved potential avenues for newly emerging zoonotic influenza in the future

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