Understanding Mycoplasma hyosynoviae
A lesser-known species affecting pigs
By Maria Pieters and Haley Schwecke
The mention of Mycoplasma in pigs is generally related to respiratory disease, as problems such as enzootic pneumonia or the Porcine Respiratory Disease Complex can result after infection with Mycoplasma hyopneumoniae, which is a well-known bacterium that can be detected in swine worldwide. Only less frequently, one thinks about other Mycoplasma species that can affect swine health.
However, an increase in detection of M. hyosynoviae has been evidenced in the most recent decade, as problems caused by the agent have become more apparent and its management and treatment more necessary. The health problems caused by M. hyosynoviae are associated with pig lameness during the finishing phase of production.
Research data and textbook information suggest M. hyosynoviae to be a commensal bacterium capable of inducing disease. In other words, although the agent can induce a series of clinical signs in infected animals, it can also be detected, and actually is, in a large proportion of pigs that are apparently healthy. Thus, establishing a solid diagnostic of M. hyosynoviae infection can be a difficult task, even for experienced pathologists.
Several assays and techniques have been develop to aid diagnostic investigations, with various degrees of success. Nevertheless, one aspect is very clear, that the interpretation of diagnostic results for M. hyosynoviae is extremely challenging and unanswered questions remain.
For instance, Mycoplasma hyosynoviae can detected through bacterial culture, although the success of growing the agent in laboratory conditions is very low, compared to other pathogens. For that reason, bacterial isolation is not usually attempted and detection of the agents is mainly based on the application of detection of genetic material via PCR testing.
Another commonly employed manner to identify exposure to an agent is by detecting antibodies produced against it in the host, and for that purpose, ELISA testing is one of the most common assays. The issue in this case is that being a commensal bacterium, development of antibodies may not be the result of an active infection, and more importantly the humoral (antibody) immune response for M. hyosynoviae has been poorly characterized.
In other words, even though antibodies to M. hyosynoviae can be identified, the meaning and implications of such results can be far from that of a previous true infection. Detecting M. hyosynoviae antibodies may not necessarily mean that the bacterium is causing lameness in the pigs. Therefore, it is imperative to characterize the immune response of pigs to M. hyosynoviae in order to identify possible opportunities to successfully apply treatment or preventative options. This approach has been the one we have taken and by collecting a large number of samples from various production systems in multiple locations, an attempt to describe the antibody profile against M. hyosynoviae has been performed.
Our research laboratory has investigated patterns of M. hyosynoviae seroconversion and antibody profiling to better understand the dynamics of host response to the bacterium. Based on the information obtained so far, antibodies against M. hyosynoviae have been detected in a high proportion of dams at various stages in the production cycle. For the most part, maternal antibodies are successfully transferred from the sow to the piglet via colostrum and those antibodies slowly wane as pigs grow and head to late nursery and finishing.
The real significance and disease protective potential of antibodies against M. hyosynoviae may be complex and require research efforts to clarify it. Moreover, the next logical questions can be:
Do antibodies provide protection from disease in piglets?
Is the high antibody level in sows a reflect of significant agent circulation in the farm?
Should pigs be boosted to maintain a high level of antibodies?
And if so, what would be the timing for that?
These and other questions are keeping investigators at the Mycoplasma Research Laboratory (UMN) busy and promise to provide insightful results to help design strategies for the control of swine lameness in the field.
Pieters is an associate professor and Schweke is a graduate student research assistant, both in the Veterinary Population Medicine Department, College of Veterinary Medicine, University of Minnesota.
