Piglets.

2020-21 Rapid Ag: A Comprehensive Approach to Elucidate the Detection of Mycoplasma Hyopneumoniae in Processing Fluids and Its Potential for Disease Monitoring and Surveillance

May 17, 2019

Principal Leader

Maria Pieters

Department

Veterinary Population Medicine

The Problem

Processing fluids (PF) are a cost-effective tool to monitor breeding herds for certain swine pathogens. PF accumulate at the bottom of containers with tails and testicles after tail docking and castration. Early in 2018, our group investigated the first report of Mycoplasma hyopneumoniae (M.hyopneumoniae) detection in PF. M.hyopneumoniae infections are highly prevalent and significantly affect the swine industry, with infections historically restricted to the respiratory tract. Thus, detection of the bacterium in PF is a conflicting finding. Results from our investigation showed M.hyopneumoniae in PF over a two-month period in 50% of daily-pooled samples. PF obtained from several positive farms yielded M.hyopneumoniae detection, while no positive results have been obtained in negative farms. The source of M.hyopneumoniae in PF has not been determined, generating crucial questions regarding potential systemic circulation of the bacterium or environmental contamination. Therefore, this investigation is designed to characterize the nature of PF, explore the potential source of M.hyopneumoniae in PF, and evaluate the feasibility of PF for M.hyopneumoniae monitoring in breeding herds. This project will provide answers to newly raised questions in the epidemiology and pathogenesis of M.hyopneumoniae, which constitute significant risks that could to succumb the bases of common approaches for disease elimination.

Background

Mycoplasma hyopneumoniae is the causative agent of enzootic pneumonia, a chronic respiratory condition affecting pigs worldwide (Thacker and Minion, 2012). Pigs infected with M. hyopneumoniae exhibit a dry cough that is associated with significant production losses (Maes et al., 2017). Besides being chronic and endemic, M. hyopneumoniae infections can act as door openers for other respiratory diseases of viral or bacterial origin. Thus, M. hyopneumoniae infections are of significant importance to swine producers.

Pig management practices, such as tail docking and castration, often known as processing, are implemented in most intensive production swine farms in the U.S. Processing of piglets is usually performed between 1 and 5 days of age. The removed tissues (i.e. tails and testicles) are collected in a container to avoid debris leftover that could promote the spread of pathogens in the farrowing room. Blood and fluids obtained from the tails and testicles accumulate at the bottom of the container, and are termed processing fluids (PF). PF have become a potential pooled sample to evaluate presence of various disease causing agents (e.g. Porcine Reproductive and Respiratory Syndrome virus - PRRSv). The use of PF to detect PRRSv is increasing among producers and veterinarians (Lopez et al., 2018; Vilalta et al., 2018). However, the use of PF for detection of bacterial infectious agents endemic to the sow farm, such as M. hyopneumoniae, has not been investigated. The most obvious reason for the lack of information on M. hyopneumoniae detection in PF would be that the pathogen is considered to be restricted to the respiratory tract of the pig, suggesting that no systemic circulation of the bacterium occurs (Thacker and Minion, 2012). In fact, sample types generally used for M. hyopneumoniae detection are those of the upper and lower respiratory tract (Sibila et al., 2009; Fablet et al., 2010; Pieters et al., 2017).

Preliminary data from our research team identified M. hyopneumoniae in 38% (8/21) PF obtained from testicles, using a species-specific real-time PCR. The farm in which positive samples were obtained was positive for M. hyopneumoniae but considered stable, as no clinical signs were evident at the time of sample collection. Furthermore, in our results an Odds Ratio of 3.2 times of being detected positive was observed in gilt litters, when compared with litters of multiple parity sows. Additionally, PF obtained from several other farms where M. hyopneumoniae is endemic have resulted positive for detection of the bacterium. In contrast, a minimal sample size in negative farms has yielded negative for detection of the pathogen. These results, along with those of other diagnostic laboratories, seem to contradict the common knowledge that M. hyopneumoniae does not circulate systemically in pigs, and have certainly challenged our understanding of the epidemiology and pathogenesis of this microorganism. Interestingly, information available in the literature could support the described findings as well as potential implications. Mycoplasma pneumoniae, a human mycoplasma previously associated to the respiratory tract has been detected in the reproductive tract of both males and females suggesting sexual transmission (Goulet et al., 1995; Scagni et al., 2008). Furthermore, M. hyopneumoniae and several other Mycoplasma species have been reported directly associated with semen or spermatozoids, both either intra or extracellular (Schulman et al., 1974; Svenstrup et al., 2003; Sylla et al., 2005; Diaz-Garcia et al., 2006; Wrathall et al., 2007). Finally, a Finnish research pointed the semen as the most likely cause of a M. bovis outbreak in two naïve herds by linking the affected animals with the sperm of a donor bull (Haapala et al., 2018). Thus, sexual contact and semen could be likely routes of Mycoplasma transmission that definitely deserve investigation.

This study proposes to tackle several of the questions already in the field in reference to the epidemiology and pathogenesis of M. hyopneumoniae that can have significant potential economic implications. M. hyopneumoniae can be eradicated from breeding herds (Holst et al., 2015). Eradication is a cost-effective approach in the long term but requires expensive antimicrobial treatment and investment of resources (Maes et al., 2017). Once eradication has been achieved, maintaining a M. hyopneumoniae free herd involves high biosecurity and only allowing the introduction of pathogen-free pigs. However, when it comes to semen this is usually purchased from boar studs which M. hyopneumoniae status maybe unknown or known M. hyopneumoniae positive. Deciphering the implications that semen could have in the transmission of the disease will rule out a potential uncontrolled way of transmission to date and potentially lead to a better rate of success in maintaining the naïve status of the herd. Furthermore, we propose to carry a comprehensive investigation in collaboration with swine practitioners, producers, and accredited swine pathologists in order to uncover the basis of the MH detection in PF. Thus, it can be hypothesized that PCR detection of M. hyopneumoniae in PF can be used as a tool for monitoring the status for this pathogen in sow farms, as the sensitivity seems to be higher than that achieved with other sample types in pre-weaning pigs. Therefore, the overall goal of this study is to elucidate the detection of M. hyopneumoniae in PF and the potential implications on monitoring and disease spread.

Objectives and Goals

The main goal of this investigation is to characterize the detection of M. hyopneumoniae in PF, identifying probable sources of the bacterium, and to evaluate the potential use of PF in monitoring and surveillance programs. In order to achieve the main goal, the following objectives are proposed:

  1. To profile the composition of PF
  2. To evaluate the detection of M. hyopneumoniae in PF, tissue, and secretions from the reproductive tract of pigs from infected farms
  3. To evaluate the detection of M. hyopneumoniae in environmental samples in farrowing rooms
  4. To assess the use of PF as a monitoring tool for M. hyopneumoniae in positive breeding herds

References

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