Polymorphisms in Pattern Recognition Receptor Genes Are Associated with Respiratory Disease Severity in Pig Farms

SIMPLE SUMMARY: Infections such as respiratory diseases pose major problems in pig production. We evaluated how these polymorphisms affect pattern recognition receptor genes, altering molecular function and reducing respiratory disease on two pig farms with different health conditions. Three polymorphisms were associated with respiratory disease severity, and they responded differently to two pneumonia pathogens, Mycoplasma hyopneumoniae, and Actinobacillus pleuropneumoniae, which showed different invasion levels on each farm. Likewise, the respective effects of each polymorphism were more pronounced on the different farms, depending on the severity of the symptoms. These findings demonstrate the possibility of using a combination of immune-gene-located DNA markers to reduce respiratory diseases caused by bacterial pathogens in pig breeding. ABSTRACT: Reduced productivity caused by infections, particularly respiratory diseases, is a serious problem in pig farming. We have previously reported polymorphisms in porcine pattern recognition receptor genes affecting molecular functions and demonstrated that the 2197A/C polymorphism in the nucleotide-binding oligomerization domain containing 2 (NOD2) gene influences porcine circovirus 2-induced mortality. Here, we investigated how these polymorphisms affect respiratory disease-induced lesions, using samples from a slaughterhouse dealing with pigs from two farms. Lung lesions were evaluated using two scoring systems, Goodwin (GW) and slaughterhouse pleuritis evaluation system (SPES), to determine the influence of Mycoplasma hyopneumoniae (Mhp) and Actinobacillus pleuropneumoniae (App), respectively. SPES scores were significantly higher when the 1205T allele of Toll-like receptor 5 (TLR5-1205T), rather than TLR5-1205C, was present. On the farm with more severe Mhp invasion, lower GW lesion scores were significantly associated with the presence of the NOD-like receptor family pyrin domain containing 3 (NLRP3)-2906G allele; where App invasion was worse, lower SPES scores were significantly associated with the presence of the NOD2-2197C allele. Combinations of polymorphisms in pattern recognition receptor genes can therefore be utilized for breeding for resistance against respiratory diseases in pigs. DNA markers of these polymorphisms can thus be used to improve productivity by reducing respiratory diseases due to bacterial pathogens in pig livestock.