PCR detection of Mycoplasma hyopneumoniae in piglet processing fluids in the event of a clinical respiratory disease outbreak

Dr. Vilalta and collaborators from the University of Minnesota provide new insights for the potential use that processing fluid (PF) may have to detect M. hyopneumoniae in breeding farms by bringing us a clinical case published in VetRecord Case Reports.


  • Genetic material of Mycoplasma hyopneumoniae from PF was quantified by real-time PCR.
  • The origin of M. hyopneumoniae genetic material detected in PF needs to be clarified.
  • Processing fluids are a potential sample to detect M. hyopneumoniae in breeding herds.

Clinical case description

The sow farm included in the study was located in the US Midwest and housed approximately 5450 sows and gilts. For the purpose of monitoring PRRSV, PF were collected weekly starting in March 2018. By then, the farm was deemed as clinically stable for PRRSV and negative for M. hyopneumoniae. An outbreak of respiratory disease, initially characterised by sudden coughing in the farrowing and gestation units, appeared during the first week of August 2018. A battery of diagnostic laboratory tests confirmed the coexistence of M. hyopneumoniae along with other bacteria and porcine circovirus type 2.


The farm routinely tested three pooled PF of approximately 15 litters each on a weekly basis. Once confirmed a respiratory disease outbreak with M. hyopneumoniae involvement, a retrospective investigation was performed on the collected PF. A total of 90 PF samples, from March 19 to October 8 2018, were tested for M. hyopneumoniae using real-time PCR.

For more information regarding the clinical case description, sample collection and testing, please refer back to the full manuscript on the journal’s webpage.


All PF tested negative, except for three suspect samples (Ct 37-40) collected while the clinical respiratory disease outbreak was taking place. The tweleve individual litter PF gathered in one of the positive samples were available for further testing. All litter PF tested negative, except for one litter with a Ct value of 32.21. In addition, all suspects and this last positive sample could be relatively quantified using a standard curve method (Figure 1), which confirmed the presence of M. hyopneumoniae genetic material in PF. 

Figure 1. Real-time PCR standard curve graphically represented as a semi-log regression line plot of Ct value vs. log of input DNA. Blue dots represent the ten-fold serial dilutions of the control DNA whereas the green squares represent the retested PF samples.

To read the results in more detail, refer to the full manuscript here.


Diagnosis of early infection with Mycoplasma hyopneumoniae in breeding herds remains challenging. Mycoplasma hyopneumoniae has been recently detected in PF, an emerging sample suitable for porcine reproductive and respiratory syndrome virus monitoring in pig breeding farms. This clinical report describes the unusual detection of M. hyopneumoniae in PF at the same time that a clinical respiratory disease outbreak occurred in a previously M. hyopneumoniae-negative sow farm. These results provide new insights into the value that testing PF to detect M. hyopneumoniae may have in breeding herds.

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