VALUTAZIONE DEI FATTORI PREDISPONENTI E STUDIO MORFOLOGICO E ISTOPATOLOGICO DELLE LESIONI POLMONARI IN SOGGETTI INFETTI DA MYCOPLASMA HYOPNEUMONIAE VACCINATI E NON VACCINATI

Mycoplasma hyopneumoniae (Mh) and several predisposing factors are involved in the pathogenesis of enzootic pneumonia (PEN). The aim of this study was to investigate the correlation between farm management factors and PEN associated pulmonary lesions in slaughtered pigs. One thousand one hundred and three lungs of fattened pigs from 18 different vaccinated and unvaccinated batches from Italian swine farms were macroscopically examined. Data related to production system, management practices and vaccination protocols were collected. One hundred and ten lung tissue samples were formalin and zinc salts ixed for histopathological and immunohistochemistry studies to detect Mh, B- and T-lymphocytes, and macrophages antigens. Our study revealed that open cycle, growing-inishing weight lower than 30 kg, presence of slatted systems and mixed natural and forced ventilation systems are important predisposing factors. Macroscopic and histopathologic studies demonstrated that vaccinated subjects have less severe lung lesions. In vaccinated pigs without pulmonary lesions and increase in B-lymphocytes was detected in BALT and inter-alveolar septa. Vaccinated pigs with PEN lung alterations had a decrease of B-lymphocytes in BALT, bronchiolar wall and interalveolar septa and an increased number of T-lymphocytes in inter-alveolar septa and macrophages in BALT, bronchiolar wall and inter-alveolar septa. Our study evidenced the main risk factors involved in the pathogenesis of PEN. A positive humoral tissue immune response was evident in vaccinated pigs without lung lesions. while vaccinated animals with pneumonia showed a reduction of B-lymphocytes and an increased Th1 response.