ABSTRACT
Mycoplasmal pneumonia of swine causes considerable economic losses in porciculture. Diverse agents, such as environmental stress and infectious microorganisms, increase the possibility of infection, an the damage to pulmonary tissue when the infection is established. It is known that Mycoplasma hyopneumoniae has an important role in this desease, in addition to secondary microbial agents, susch as Pasteurella mutocida and Actinobacillus pleuropneumoniae. However, the characteristics of this disease in farms are well known. In this work we review the interactions among the different microorganisms involved and the immunological strategies utilized to control this disease. The interaction between Mycoplasma hyopneumoniae and P. multocida in experimental pneumonia was reported by us in conventional pig. M. hyopneumoniae causes mild pneumonia, whereas P. multocida aggravates the pneumonia initiated by M. hyopneumoniae. The disease has been reproduced to test the efficacy of two immunogens, and can also be used to evaluate some antibiotics. A M. hyopneumoniae bacterine administered intraperiotoneally conferred more protection than when it was used with adjuvant, although protection was not complete and colonization by M. hyopneumoniae was not prevented, as is claimed to have been the case with other vaccines