Monitoring for Mycoplasma hyopneumoniae before and after a partial depopulation program using a typing scheme based on the polyserine repeat motif of pl46

Abstract

Mycoplasma hyopneumoniae diversity was determined using a molecular typing method based on the polyserine repeat motif within the pi 46 gene. Three related Argentinian farms (A, B, and C) were investigated. To obtain a population free of enzootic pneumonia on Farm C, a partial depopulation program had been carried out first on Farm A and then on Farm B. Finally, Farm C was populated with early-weaned piglets from Farm B. To evaluate the success of the partial depopulation program, thefarms were monitored for clinical signs and by serological testing, lung examination at slaughter, and nested polymerase chain reaction (nPCR). It was concluded that they were free of enzootic pneumonia, but M hyopneumoniae remained despite the eradication measures applied. An outbreak of enzootic pneumonia in Farm C triggered an investigation of M hyopneumoniae genetic diversity in these farms. For this purpose, all DNA samples obtained from PCR-positive nasal swabs were further characterized using another nPCR designed for Mhyopneumoniae typing.Several M hyopneumoniae types were identified in these farms, but one strain seemed to be present before and after the application of the partial depopulation program. Unambiguous discrimination of M hyopneumoniae would require analysis of other genomic regions.