Avaliação molecular e histopatológica da infecção por Mycoplasma hyopneumniae em pulmão de suínos submetidos ao abate em São Luís-MA

Abstract

Brazil occupies a prominent position in the world agribusiness, supported by low production costs and the improvement in zootechnical indices. Currently, the country is the world's fourth largest producer and exporter of pork, with more than 80% of its production destined for the domestic consumer market. In this context, Porcine Enzootic Pneumonia (PES), whose main causative agent is the bacterium Mycoplasma hyopneumoniae, is reported as the main cause of respiratory problems in swine, and its occurrence makes the host susceptible to secondary bacterial and viral agents. Due to the great impact of pneumonia on the swine production chain and the need for a better understanding of the epidemiology and pathogenesis of this disease that contributes to the definition of more effective control measures, which consequently lead to the reduction of the economic impact generated in production systems of pigs. The research aims to evaluate the infection by M. hyopneumoniae in swine, already described in other states, but not yet reported in the state of Maranhão. Therefore, this work aims to investigate the presence of Mycoplasma hyopneumoniae in swine submitted to slaughter in São Luís Island - MA, using molecular and histopathological diagnostic methods. For this, 150 lung samples were collected from pigs obtained from supervised and unsupervised slaughter on São Luís Island, Maranhão, from July 2019 to August 2021. Being random sampling, 65 from supervised slaughter and 85 from slaughter not supervised. Of the 150 DNA samples collected, 121 showed an amplified product for Cyt B in the PCR assay. Thus, 121 samples were submitted to analysis of M. hyopneumoniae by qPCR, of which 44 were positive, thus representing a percentage of 36.36%. The average amount of bacterial load ranged from 1.20 x 101 to 7.20 x 104 between samples, with an average of 1.73 x 104 copies. Of the reagent samples, 81.81% (36 samples) came from unsupervised slaughter, marketed at open markets, while 18.18% (8 samples) came from an supervised slaughterhouse. In the histopathological analysis, of the 44 positive samples in the qPCR, 30/44 had findings consistent with inflammatory processes, which included the presence of BALT hyperplasia, pneumocytes, alveolar edema, hemorrhage, congestion and emphysema. The microscopic findings associated with the quantifications show that there is a relationship between the quantification of the pathological agent and the presence of microscopic lesion, demonstrating that the greater bacterial load in the lung tissue is associated with the greater histopathological staining for BALT hyperplasia, since the 3 samples higher bacterial load (qPCR: 5.63 x 103, 2.19 x 104 and 7.23 x 104) were the ones that most evidenced this finding.