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Mycoplasma Hyopneumoniae Surveillance – A Production System Approach for Health Management Decision Making

Shamus Brown, Eduardo Fano, Nathan Schaefer, Katie Wedel, Maria PietersJune 7, 2016

INTRODUCTION 

Mycoplasma hyopneumoniae (M. hyo) is a common etiologic agent that causes economic losses in all production stages of our system. 

The pathogenesis of disease is unknown and variable across the 38 sow flows. 

The goal in this project was to develop a surveillance program to successfully classify the M. hyo status and strain within three distinct production flows. 

By routinely testing the gilt development units (GDU), sow farms, and downstream pigs of each flow, we can determine the timing of M. hyo colonization and infection dynamics within the system to develop systematic intervention methods to reduce or eliminate the clinical impact.

MATERIALS AND METHODS 

Historical wean-to-finish (wtf) diagnostics identified three sow farms experiencing clinical M. hyo. 

Each sow farm represents one of three distinct genetic flows. 

At each sow farm, 30 laryngeal swabs were collected from gilts entered into the sow farm 8 weeks prior from the GDU, at expected peak M. hyo shedding, to prove M. hyo instability. 

Swabs were tested individually by real-time PCR at the BIVI HMC, Ames, IA. Positive PCR samples were sent to the University of Minnesota VDL for sequencing and a comparative dendrogram developed. 

After baseline sow farm sampling, additional laryngeal swabs were tested at the gilt grow-finish, GDU, and wtf at approximately 8 weeks placed.

RESULTS 

Gilts in Flow A 

  • Tested negative for M. hyo at the grow-finish and GDU 

  • 27 % of gilts tested positive at the sow farm 

  • No wtf pigs have tested positive for M. hyo, but sampling is ongoing 

Gilts in Flow B 

Tested negative for M. hyo at the grow-finish and GDU 

  • 27 % of gilts tested positive at the sow farm 

  • 24 % of wtf pigs were positive 

Gilts in Flow C 

  • Tested negative for M. hyo in grow-finish 

  • 40 % of gilts tested positive at the GDU 

  • The sow farm and wtf both tested negative 

Sequence results showed each multiplication flow has a unique M. hyo strain with 99 % + homology consistent across each production stage. 

The three flows are 97 % homologous, but each flow has a distinct dendrogram cluster.

CONCLUSION AND DISCUSSION

The results have led to discussion about M.hyo stabilization and elimination programs. 

The keys to successful implementation will be: 

  • Early gilt acclimation 

  • 250+ day cool down to clear active infection before first farrowing 

The previously described surveillance strategy utilizing laryngeal swabs will be used to confirm the cessation of M. hyo shedding prior to gilt entry into the sow farms. 

Sequencing and dendogram development have been helpful epidemiological tools that allow agent tracking and support the system approach.

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