The last issue of the Journal of Swine Health and Production featured a practice tip written by Dr. Rebecca Robbins from Seaboard Foods, in collaboration with Dr. Maria Pieters and the MycoLab. This publication has for objective to share a safe, reliable and herd-specific technique to expose gilts to Mycoplasma hyopneumoniae.
Create a lung-homogenate to expose animals to M. hyopneumoniae in order to stimulate immunity and decrease the circulation of the pathogen in the herd.
Creating the lung homogenate
Lungs from an animal displaying clinical signs of enzootic pneumonia were harvested. Diagnostic testing confirmed that the lungs were indeed infected with M. hyopneumoniae but did not host other respiratory pathogens. Both macropscopic lesions and PCR testing were conducted to select the appropriate set of lung tissues.
Then, a naive animal was chosen to amplify M. hyopneumoniae i.e. to allow the pathogen to multiply and therefore, ensure a sufficient quantity of mycoplasms in the lung at harvesting. These animals were inoculated with a solution made of blended lung tissue from the initial donor (described in the previous paragraph). Lungs from the amplifiers were harvested 5 weeks post-inoculation but only if the animals were tested positive for M. hyopneumoniae by PCR testing on laryngeal swabs.
Evaluation of the lung homogenate
The homogenates created from the amplifiers’ lung tissue were then evaluate for their stability and their infectivity. 38 animals were inoculated with the homogenate and all of them were tested PCR positive for M. hyopneumoniae.
Multiple locus variable number tandem repeat analysis (MLVA) was used to evaluate the stability of M. hyopneumoniae genome. All of the samples tested showed to be of an identical type, confirming the stability of the genome.
Summary of the article
The swine industry is known for holding high standards of disease control and elimination. However, partial disease control for Mycoplasma hyopneumoniae at the farm level has been evident and has driven initiatives for unconventional health management strategies. Several approaches focused on gilt exposure for M hyopneumoniae using a herd-specific lung homogenate have been performed in the field. Nevertheless, variations in efficacy are apparent and a publicly available protocol for producing M hyopneumoniae lung homogenate under field conditions is not available. In this practice tip, a protocol is described for developing a herd-specific lung homogenate for M hyopneumoniae exposure intended for use in veterinary-supervised elimination or control programs. A herd-specific lung homogenate inoculum, free of secondary respiratory pathogens for the herd of intended use and with an adequate M hyopneumoniae concentration, was obtained through extensive diagnostic testing and evaluation of M hyopneumoniae localization within the lung. Molecular methods were applied to characterize the M hyopneumoniae present in the lung and to evaluate the genomic stability of the bacterium during the exposure process. In doing so, a herd-specific M hyopneumoniae lung homogenate for gilt acclimation was obtained under field conditions.