Molecular serotyping of Haemophilus parasuis isolated from diseased pigs and the relationship between serovars and pathological patterns in Taiwan

Wei-Hao Lin; Hsing-Chun Shih; Chuen-Fu Lin; Cheng-Yao Yang; Yung-Fu Chang; Chao-Nan Lin; Ming-Tang Chiou

doi:10.7717/peerj.6017

Molecular serotyping of Haemophilus parasuis isolated from diseased pigs and the relationship between serovars and pathological patterns in Taiwan

PeerJ. 2018 Nov 29:6:e6017. doi: 10.7717/peerj.6017. eCollection 2018.

Authors

Wei-Hao Lin^{1

2}, Hsing-Chun Shih², Chuen-Fu Lin³, Cheng-Yao Yang⁴, Yung-Fu Chang⁵, Chao-Nan Lin^{1

2}, Ming-Tang Chiou^{1

2

6}

Affiliations

¹ Department of Veterinary Medicine, College of Veterinary Medicine, National Pingtung University of Science and Technology, Pingtung, Taiwan.
² Animal Disease Diagnostic Center, College of Veterinary Medicine, National Pingtung University of Science and Technology, Pingtung, Taiwan.
³ Department of Veterinary Medicine, College of Veterinary Medicine, National Chiayi University, Chiayi, Taiwan.
⁴ Graduate Institute of Veterinary Pathobiology, College of Veterinary Medicine, National Chung Hsing University, Taichung, Taiwan.
⁵ Department of Population Medicine and Diagnostic Sciences, College of Veterinary Medicine, Cornell University, NY, USA.
⁶ Research Center for Animal Biologics, National Pingtung University of Science and Technology, Pingtung, Taiwan.

Abstract

Background: Haemophilus parasuis is the etiological agent of Glässer's disease, and causes severe economic losses in the swine industry. Serovar classification is intended as an indicator of virulence and pathotype and is also crucial for vaccination programs and vaccine development. According to a polysaccharide biosynthesis locus analysis, H. parasuis isolates could be classified by a molecular serotyping assay except serovars 5 and 12 detected by the same primer pair. The aim of this study was to identify H. parasuis isolates from diseased pigs in Taiwan by using a molecular serotyping assay and to analyze the relationship between serovars and pathological patterns.

Methods: From August 2013 to February 2017, a total of 133 isolates from 277 lesions on 155 diseased animals from 124 infected herds serotyped by multiplex PCR and analyzed with pathological data.

Results: The dominant serovars of H. parasuis in Taiwan were serovars 5/12 (37.6%), 4 (27.8%) and 13 (15%) followed by molecular serotyping non-typable (MSNT) isolates (13.5%). Nevertheless, the serovar-specific amplicons were not precisely the same sizes as previously indicated in the original publication, and MSNT isolates appeared with unexpected amplicons or lacked serovar-specific amplicons. Most H. parasuis isolates were isolated from nursery pigs infected with porcine reproductive and respiratory syndrome virus. The percentage of lung lesions (30.4%) showing H. parasuis infection was significantly higher than that of serosal lesions.

Discussion: Collectively, the distribution of serovars in Taiwan is similar to that found in other countries, but MSNT isolates remain due to genetic variations. Furthermore, pulmonary lesions may be optimum sites for H. parasuis isolation, the diagnosis of Glässer's disease, and may also serve as points of origin for systemic H. parasuis infections in hosts.

Keywords: Glässer’s disease; Haemophilus parasuis; Polyserositis; Serotyping.

Grants and funding

This study was supported by the Animal Disease Diagnostic Center, College of Veterinary Medicine, National Pingtung University of Science and Technology, Taiwan. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.