Frequency and severity of enzootic pneumonia-like lesions in Greek swine herds and their association with different vaccination protocols against Mycoplasma hyopneumoniae

Several European countries, but Greece, reported data of Enzootic Pneumonia (EP)-like lesions at slaughter. In the present study, frequency and severity of EP-like lesions were evaluated at slaughter and their association with different vaccination protocols for Mycoplasma hyopneumoniae, the primary pathogen of EP, was investigated, in Greek swine herds. In total, 7047 lungs from 53 farrow-to-finish herds were scored at slaughter by using the Ceva Lung Program TM tool, from January 2016 to December 2019. The frequency of EP-like lesions was 47.6% and the median (range) of the total lung lesions score was 0 (0-25). Pigs, which were vaccinated with a monovalent vaccine for M. hyopneumoniae either once or twice and those which received an extra shot, were less likely to have EP-like lesions, compared to pigs that received a bivalent vaccine containing both M. hyopneumoniae and PCV2 antigens. For the pigs which received two shots of a monovalent vaccine, the odds of higher versus lower lung lesion score(s) were lower compared to pigs that received a bivalent vaccine. Almost half of the lungs were affected, although 98.3% of the pigs were vaccinated. Poor housing and management, commonly seen in Greek herds, may hamper the efficient reduction of M. hyopneumoniae spread.