Betlach, Alyssa2021-10-132021-10-132021-07https://hdl.handle.net/11299/225036University of Minnesota Ph.D. dissertation. July 2021. Major: Veterinary Medicine. Advisor: Maria Pieters. 1 computer file (PDF); xii, 170 pages.Mycoplasma hyopneumoniae (M. hyopneumoniae) is a prevalent respiratory bacterium known to inflict significant health challenges in swine. Opportunities to improve disease control efforts exist, as the continuation or reoccurrence of M. hyopneumoniae infection occurs. The general objective of this thesis was to provide new information on the detection, control, and molecular characterization of this microorganism. Insight in the detection and rate of pathogen spread is essential to guide surveillance and control efforts. Therefore, the detection and transmission of M. hyopneumoniae were evaluated under natural conditions. Bacterial transmission and clinical signs were not evident until several weeks after the introduction of one infected pig, highlighting the need for accurate surveillance protocols. Despite their frequent use for disease control and elimination, there is limited information on whether vaccines and antibiotics can alter the spread and persistence of M. hyopneumoniae. The effect of multiple vaccinations on M. hyopneumoniae infection and transmission was explored. Results indicated that a three-dose vaccination strategy against M. hyopneumoniae numerically reduced pathogen transmission, especially when the entire population was vaccinated. Next, the effect of medication on M. hyopneumoniae transmission and detection by PCR was evaluated during different infection phases. Medication numerically reduced the rate of new infections during the acute phase of infection. For the chronic phase, persistence of M. hyopneumoniae detection by PCR was evident for several months post-treatment. However, the infectiousness (or transmission potential) of the bacterium could not be assessed due to lack of transmission. Further research focused on the effect of control measures on M. hyopneumoniae transmission is warranted. Multiple-Locus Variable number tandem repeat Analysis (MLVA) and complete P146 gene sequencing were employed to characterize M. hyopneumoniae variants. Fair agreement in assay outcome was calculated between the two methods. Discriminatory power was higher for MLVA than the P146 sequencing. Nevertheless, similar epidemiological inferences were obtained. Using MLVA, genetic diversity of M. hyopneumoniae was evaluated across swine production flows. Insight for pathogen origin was provided based on the presence of common M. hyopneumoniae variants between finishers and the sourcing herds. In conclusion, results from this thesis highlight the importance of diagnostics and epidemiology of M. hyopneumoniae for overall disease control.enThesis or Dissertation