Effect of antibiotic treatment on Mycoplasma hyopneumoniae detection and infectious potential

Mycoplasma hyopneumoniae (M. hyopneumoniae) causes significant economic losses in the swine industry. Antibiotics with activity against Mycoplasma spp. are employed for disease mitigation and pathogen elimination. However, veterinarians are often challenged with the detection of M. hyopneumoniae by PCR after antibiotic treatment, thus raising the question whether the bacterium is still infectious. The objective of this study was to evaluate the effect of tulathromycin treatment on M. hyopneumoniae detection and infectious potential during the acute and chronic phases of infection. For each infection phase, one age-matched naïve gilt was placed in contact with one M. hyopneumoniae infected gilt that was either treated with tulathromycin, treated and vaccinated, or non-treated, for 14 days. Four replicates per treatment group were performed for each infection phase. A numerical reduction in relative bacterial load was observed in acutely treated gilts compared to non-treated gilts. The rate at which naïve gilts became infected with M. hyopneumoniae was numerically reduced when co-housed with treated, acutely infected gilts compared to those housed with non-treated, infected gilts. During the chronic infection phase, M. hyopneumoniae was detected by PCR in more than 50 % of treated infected gilts and persisted for up to three months post-treatment. Transmission was not detected in all treatment groups however, the possibility that the pathogen was infectious could not be completely ruled out. Further research focused on assessing M. hyopneumoniae detection and viability post-treatment is necessary to guide control and elimination efforts.