This is our Friday rubric: every week a new Science Page from the Bob Morrison’s Swine Health Monitoring Project. The previous editions of the science page are available on our website.
Doctors Guilherme Preis and Cesar Corzo from the University of Minnesota share with us preliminary data from a Senecavirus A (SVA) outbreak investigation in a sow herd. This research emphasizes the importance of understanding the within-herd epidemiology of this virus.
SVA is still present in the U.S. swine herds at lower levels.
SVA RNA has been consistently detected in processing fluids in the event of a disease outbreak in a sow herd.
Viral dynamics and shedding cessation in the breeding herds need to be better characterized.
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.
The Science Page this week was written by the MSHMP team and covers pooling of processing fluids. A more detailed report can be found on the blog. Currently, a study to evaluate the number of negative processing fluids to declare a farm stable is ongoing. If you are interested in participating in this study, contact Dr. Juan Sanhueza (jsanhuez-at-umn-dot-edu).
The use of processing fluids (PF) to detect and monitor PRRSvand other pathogens is increasing among producers and veterinarians. Preliminary data from our research team identified Mycoplasma hyopneumoniae in PF at the litter level, using a speciesͲspecific realͲtime PCR, in a M. hyopneumoniae endemically infected farm.
To investigate the detection of M. hyopneumoniae in non-respiratory tissues and fluids collected from suckling pigs at processing age.
To develop an in situ hybridization (ISH) assay to further identify M. hyopneumoniae in non-respiratory tissues.
Material and methods
Freshly farrowed litters were sampled at two sow farms with previous detection of M. hyopneumoniae in PF. The following samples were obtained from:
Dams: Whole blood, serum,colostrum, whole placenta and vaginal swab.
Stillborn: Individually bagged and submitted for full diagnostics M. hyopneumoniae workup at the UMN-VDL. Whole blood was also collected during sampling.
Viable piglets: New born piglets were processed prior to suckling. Tails and testicles were collected individually per piglet and gender was recorded. Whole blood and laryngeal swabs were collected for all piglets. (PPE and sampling supplies were changed or disinfected between collection for each piglet)
Daily aggregated PF were collected at a sow farmover a 10-week period. A novel RNA-based ISH was developed using hybridization-coupled signal amplification system in histological tissue sections. To aid visualization of transcriptionally active bacterial organism expressing ribosomal and adhesin proteins.
Mycoplasma hyopneumoniae detection in non-respiratory tissues or fluids
All dams tested negative for M. hyopneumoniae by RT-PCR in blood, serum, colostrum, placenta, and vaginal swabs. Fifty percent of dams were seropositive by Oxoid™ Mycoplasma hyopneumoniae ELISA. All blood samples from stillborn and piglets resulted negative to M. hyopneumoniae by RT-PCR. Mycoplasma hyopneumoniae was detected in 2/54 individual fluid samples (tails and testicles). M. hyopneumoniae was detected (Ct<40) over the 10-week period by RT-PCR (Figure 1). PF and their associated testicles were collected individually at the litter level. All PF were tested by M. hyopneumoniae by RT-PCR. Samples were fixed in formalin to perform ISH on positive samples.
Development of an In situ hybridization assay
The ISH-RNA technique established the distribution of M. hyopneumoniae in affected tissues in association with histological lesions, characterized by lymphoplasmocytic peribronchiolitis and/or hyperplasia of the broncho-associated lymphoid tissues. In M. hyopneumoniae positive lungs, hybridization signals were observed in the apical membrane of the respiratory epithelium of bronchi and bronchioles. Positive signals were also observed in inflammatory cells and degenerative epithelial cells within the bronchial and bronchiolar lumen. The ISH-RNA technique provided molecular detection of M. hyopneumoniae cells expressing mRNA of proteins and elucidated the localization patterns by visualization in tissue.
Conclusions and Implications
Mycoplasma hyopneumoniae was detected intermittently in aggregated PF. In this investigation, M. hyopneumoniae was not detected in piglet tissues or samples, regardless of M. hyopneumoniae detection in aggregated PF. Regardless of the fact that environmental contamination can not be ruled out, aggregated PF could be a good indicator of M. hyopneumoniae a farm level. A specific In situ hybridization assay for M. hyopneumoniae was developed, which will be applied to nonͲrespiratory piglet tissue samples.