Multiple vaccinations: what effect on M. hyopneumoniae infection?

Dr. Betlach and the team from the MycoLab recently published a study in the journal Vaccine, regarding the impact of multiple vaccines against Mycoplasma hyopneumoniae. They assessed bacterial load and protection against infection in gilts.


  • Vaccination against M. hyopneumoniae reduced bacterial load in infected gilts.
  • Vaccination of both infected and contact gilts reduced M. hyopneumoniae transmission.
  • Genetic diversity of M. hyopneumoniae was not influenced by vaccination.


Briefly, 32 Myco-negative gilts were enrolled in the study. Researchers infected a subset of them to create reliable seeders while the other subset remained naïve to Mycoplasma hyopneumoniae. Within each subset, some gilts were vaccinated against Mycoplama hyopneumoniae while others were not. Therefore, four groups of gilts were in this study: seeder vaccinated, seeder non-vaccinated, contact vaccinated and contact non-vaccinated. Vaccinated animals received three doses of a commercial vaccine. Tracheal and bronchial samples were tested by PCR while an ELISA was used for the collected serum samples. Additionally, the percentage of anatomic lung lobe lesions was recorded at the end of the study.


All vaccinated gilts showed antibody levels after the 3-dose vaccination protocol. Additionally, a reduction in bacterial load was found in vaccinated seeder gilts compared to the non-vaccinated ones.

No vaccinated contact gilt was found positive at the end of the study whereas three non-vaccinated contact gilts were positive: one which was in contact with a vaccinated seeder and two in-contact with non-vaccinated seeders. Therefore, vaccination of the seeder and contact animals showed protection against infection for the two weeks in which these populations were in contact and in this study.

The strains tested by Multiple-locus Variable Number tandem repeat Analysis (MLVA) showed that a single type was found in all of the positive animals tested, vaccinated or not.

Read the full article on the journal website.


Mycoplasma hyopneumoniae (M. hyopneumoniae) infections continue to result in significant respiratory challenges in the swine industry worldwide. Vaccination for M. hyopneumoniae is commonly utilized, as reduction in bacterial loads and clinical severity in vaccinated pigs have been shown. However, the effect of M. hyopneumoniae vaccination on transmission across different pig populations has been minimally investigated. The aim of this pilot study was to evaluate the effect of multiple vaccinations on M. hyopneumoniae infection, transmission, and genetic variability in infected and susceptible gilt populations. Thirty-two naïve gilts were allocated to four treatment groups: (1) Vaccinated seeder (VS); (2) Non-vaccinated seeder (NVS); (3) Vaccinated contact (VC); and (4) Non-vaccinated contact (NVC). At 5, 7, and 9 weeks of age, all gilts selected to be vaccinated received a commercial M. hyopneumoniae bacterin for a total of 3 doses. At 11 weeks of age, VS and NVS gilts were inoculated with M. hyopneumoniae to become seeders. At 28 days post-inoculation (dpi), VS and NVS gilts were individually relocated to clean experimental rooms, where they were placed in contact with one age-matched VC or NVC gilt (1:1 ratio) for 14 days. Blood and tracheal samples, bronchial swabs, and lung lesions were collected and/or evaluated for M. hyopneumoniae infection. In this study, a three-dose vaccination strategy against M. hyopneumoniae significantly reduced bacterial load in seeder gilts. Furthermore, a numerical reduction in M. hyopneumoniae lung lesions at 28 dpi was observed in VS gilts. All VC gilts in the VS:VC treatment group pairing remained Mhyopneumoniae negative, compared to other groups in which 1–2 transmission events occurred per treatment group. Results from this investigation provide insight on the potential impact of multiple vaccinations on reducing M. hyopneumoniae transmission and infection. Further research encompassing vaccinations of gilt groups in field settings is necessary to validate findings.

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