PORCINE LUNG LESIONS AT SLAUGHTER AND THEIR CORRELATION TO THE INCIDENCE OF INFECTIONS BY MYCOPLASMA-HYOPNEUMONIAE AND ACTINOBACILLUS-PLEUROPNEUMONIAE DURING THE REARING PERIOD

Porcine lungs were macroscopically and microscopically examined at sla ughter, with special regard to different stages of lesions similar to those caused by Mycoplasma hyopneumoniae. There was good conformity be tween the macroscopical and microscopical findings. In an extended aba ttoir survey, lesions were found in 4210 our of 4508 lungs examined. T he majority of lungs with pleuritic lesions (274 out of 369) revealed by the extended examination were registered by the official procedure. No correlation between pleuritis and time for seroconversion, or with the levels of antibodies to Actinobacillus pleuropneumoniae, was foun d. Among lungs affected with pneumonic lesions (n = 3841), lesions sim ilar to those caused by Mycoplasma hyopneumaniae were predominant (n = 3769). Only 15% of these lesions were revealed by official registrati on at slaughter. This figure is explained by the fact that only 35% of the infections were still active at the time of slaughter and that on ly ongoing lesions exceeding a certain magnitude were recorded accordi ng to the official regulations. By following the development of antibo dies to Mycoplasma hyopneumoniae through the fattening period, the dur ation of the active infection was estimated to be approximately 12 wee ks. Consequently, infections with Mycoplasma hyopneumoniae gained duri ng the early fattening period will, in general, escape detection at sl aughter.