Candidate genes and gene markers for the resistance to porcine pleuropneumonia

Florian Nietfeld,Hermann Willems,Christine Wurmser,Ruedi Fries,Peter Valentin-Weigand,Karl-Heinz Waldmann,Gerald Reiner,Doris Höltig

doi:10.1007/s00335-019-09825-0

Abstract

Actinobacillus (A.) pleuropneumoniae is one of the most important respiratory pathogens in global pig production. Antimicrobial treatment and vaccination provide only limited protection, but genetic disease resistance is a very promising alternative for sustainable prophylaxis. Previous studies have discovered multiple QTL that may explain up to 30% of phenotypic variance. Based on these findings, the aim of the present study was to use genomic sequencing to identify genetic markers for resistance to pleuropneumonia in a segregating commercial German Landrace line. 163 pigs were infected with A. pleuropneumoniae Serotype 7 through a standardized aerosol infection method. Phenotypes were accurately defined on a clinical, pathological and microbiological basis. The 58 pigs with the most extreme phenotypes were genotyped by sequencing (next-generation sequencing). SNPs were used in a genome-wide association study. The study identified genome-wide associated SNPs on three chromosomes, two of which were chromosomes of QTL which had been mapped in a recent experiment. Each variant explained up to 20% of the total phenotypic variance. Combined, the three variants explained 52.8% of the variance. The SNPs are located in genes involved in the pathomechanism of pleuropneumonia. This study confirms the genetic background for the host’s resistance to pleuropneumonia and indicates a potential role of three candidates on SSC2, SSC12 and SSC15. Favorable gene variants are segregating in commercial populations. Further work is needed to verify the results in a controlled study and to identify the functional QTN.

Highlights

The pathogen Actinobacillus (A.) pleuropneumoniae is a gram-negative bacterium from the genus Pasteurellaceae and one of the major bacterial pulmonary pathogens in swine (Gottschalk 2012)
The pigs tested negative in antibody tests for A. pleuropneumoniae, Haemophilus parasuis, PRRSV and Influenza A
SNP 12_14641621 on SSC12 explained up to 19.9%, SNP 15_128476618 on SSC15 up to 18.5% and SNP 2_45022788 on SSC2 up to 33% of the phenotypic variance of the respiratory health score (RHS) score (Table 4)

Summary

Introduction

The pathogen Actinobacillus (A.) pleuropneumoniae is a gram-negative bacterium from the genus Pasteurellaceae and one of the major bacterial pulmonary pathogens in swine (Gottschalk 2012). Actinobacillus pleuropneumoniae is transmitted from sow to piglets. The main problem with a vaccination strategy appears to be a low cross-immunity between serotypes (Higgins et al 1985; Fenwick and Henry 1994). Modern subunit or toxoid vaccines do not provide full protection against the clinical outbreak of the disease (e.g., reduction in mortality, increase in daily weight gain, amounts of condemnations for pneumonia) (Chiers et al 1998; Sjölund and Wallgren 2010; Jirawattanapong et al 2010; Del Pozo Sacristan et al 2014).

Objectives

Methods

Results

Discussion

Conclusion