Mycoplasma hyopneumoniae (Mhyo) is primary pathogen involved in porcine respiratory diseases complex (PRDC). The objective of this study was to evaluate Mycoplasma hyopneumoniae (Mhyo) infection in five commercial pig farms by using serology and lung lesion scoring at slaughter. Five Macedonian pig herds with a history of respiratory diseases were included in the study. Blood samples were taken from pigs at 6, 10, 14, 18, and 22 weeks of age. Ten animals per age group from each farm were sampled and tested for antibodies to Mhyo. At abattoir, 50 lungs per farm were scored for lesions associated with enzootic pneumonia (EP). All farms were seropositive to Mhyo. Higher seroprevalence to Mhyo was observed in grower and finisher pigs, while significant difference (p<0.001) was detected among farms in 10-, 14-, and 22-week-old pigs. Enzootic pneumonia-like lesions were detected in 91.2% of all tested lungs with range of 82 to 98% on farm level. Mean lung lesion score (LLS) obtained for all farms was 11.5 (8.04–14.4). Significant difference for LLS and significantly higher percentage of severe LLS grade (>10) were found among some of the farms (p<0.001). In conclusion, high seroprevalence to Mhyo in finishing pigs in most of the farms was most likely due to vaccination. Farms with higher seroprevalence to Mhyo obtained lower LLS. Serology monitoring of different pig categories and lung assessment at slaughterhouse is a practical tool for assessing vaccine efficacy of Mhyo in pig farms.
