Comparison of transmission of Mycoplasma hyopneumoniae in vaccinated and non-vaccinated populations

A transmission experiment was performed to quantify the effect of vaccination on the transmission of Mycoplasma hyopneumoniae ( M. hyopneumoniae) in nursery piglets by means of an adjusted reproduction ratio ( R n ). Thirty piglets, vaccinated at 1 week of age, and 30 non-vaccinated piglets, free of M. hyopneumoniae, were housed in six separate pens. In each pen, three animals that were intratracheally inoculated with M. hyopneumoniae, were housed together with seven contact piglets during the conventional nursery period of 6 weeks. At the end of the study, the infectious status of the animals was determined based on results of nPCR performed on bronchoalveolar lavage fluid. The R n -value in the vaccinated group was 2.38 (1.07–7.53) while in the non-vaccinated group, an R n -value of 3.51 (1.51–9.34) was observed, both not significantly different from each other ( p = 0.77). Under the actual experimental conditions, transmission of M. hyopneumoniae in nursery piglets was only numerically lower in vaccinated groups. In addition, vaccination with a conventional vaccine could not prevent the establishment of M. hyopneumoniae organisms in the lung.