Control of infections with Mycoplasma hyopneumoniae in swine herds by disrupting the chain of infection, disinfection of buildings and strategic medical treatment.

A program with the aim to eliminate infections with Mycoplasma hyopneumoniae was applied in 4 herds selling breeding pigs. A "fast" (1 month) variant of the program was applied in one herd selling young gilts (30 kg body weight) and in one herd selling adult breeding stock, and a "slow" (> or = 3.5 months) variant was applied in two corresponding herds. In both variants, the spread of infections was prevented by isolating the breeding stock. These animals were treated with tiamulin before being reintroduced to the original, but emptied and disinfected units. Further, the rearing of pigs born before and after initiating the program was separated. In both herds selling young gilts, no antibodies to Mycoplasma hyopneumoniae were detected in sera collected for at least 40 months after finishing the program. In the herds selling adult breeding pigs, elimination of infections with Mycoplasma hyopneumoniae was only achieved by the "fast" variant, while the infections still were present in the breeding herd using the "slow" variant of the program. The failure of the program in the latter herd was probably due to turbulent air flows between ventilation systems of units situated close to each other and simultaneously housing uninfected and infected pigs.