Mycoplasma hyopneumoniae genetic variability within swine production flows

ithin swine production flows

In this recent publication in the Canadian Journal of Veterinary Research, Dr. Alyssa Betlach from the MycoLab at the University of Minnesota investigates the genetic variability of Mycoplasma hyopneumoniae within and across various production flows within a single system.

Key points

  • Multiple-locus variable-number tandem repeat analysis allows to detect genetic variability between M. hyopneumoniae strains.
  • Four production flows were sampled over a duration ranging from 4 months to 3 years.
  • Between 1 and 6 variable-number tandem repeat (VNTR) types were found within the four production flows.
  • VNTR types in growing sites seem to originate from their respective breeding herds.


Four production flows were enrolled within one Midwest production system. Samples were taken from all four stages of production, from the gilt development unit to the finishing barn, across several herds for each of the production flows. A total of 262 bronchial or laryngeal swabs were collected over a time period ranging from 4 months to 3 years. Samples were then tested by PCR and multiple-locus variable-number tandem repeat analysis. Based on the results, a minimum spanning tree was created to illustrate genetic diversity between strains.


Around 45% of the samples were positive for M. hyopneumoniae and a variable-number tandem repeat (VNTR) type was obtained in 89% of the samples for which the analysis was attempted. Between 1 and 6 VNTR types were found within flows for a total of 15. One dominant type was observed across the four production flows and one identical type was found in the GDU and growing sites for a period of 4 months to 2 years within three of the four flows. In this study, VNTR types in the nursery and finishing sites seemed to derive from their respective breeding herds. Overall, there was minimal genetic variation within and across production flows.

Read the full publication to see the genetic tree.


The aim of this study was to assess the genetic variability of Mycoplasma hyopneumoniae within various swine production flows. Four M. hyopneumoniae positive production flows, composed of 4 production stages, were selected for this study. Laryngeal and/or bronchial swabs were collected from each production stage within a flow, for a period of 4 months up to 3 years. A multiple-locus variable-number tandem repeat analysis was performed to assess the genetic variation of M. hyopneumoniae within and across production flows through the identification of variable-number tandem repeat (VNTR) types. A maximum of 6 M. hyopneumoniae VNTR types were identified in a single flow, in which VNTR types appeared to be flow specific. An identical VNTR type was detected across several production stages for up to 3 years. In this study, minimal M. hyopneumoniae genetic variation was evidenced within and across production flows.