The detection of Mycobacterium bovis (M. bovis) in environmental samples with precision is imperative to control bovine tuberculosis (bTB) infections at the herd level, as residual M. bovis remains one of the major causes of recurring infections. In this study, a nested PCR method for the detection of M. bovis in environmental samples was applied to identify potential environmental reservoirs of the bacterium. A set of 200 environmental samples (167 fecal samples and 33 water samples) from 39 herds with a history of bTB outbreak was analyzed using a nested PCR method to detect residual M. bovis. Amplicon libraries of the IS6110 target gene fragment were amplified from M. bovis DNA using two established primer sets. A positive nested PCR result was observed in 69.5% of fecal samples and 66.7% of water samples, thus showing that residual M. bovis was present in the environmental samples of bTB-positive herds in a high proportion. This study is the first to demonstrate high levels of M. bovis DNA in environmental samples and to show that environmental reservoirs of this pathogen contribute to recurring outbreaks of bTB. Environmental monitoring of herds in which bTB outbreaks have occurred with high sensitivity and specificity is expected to help prevent the recurrence of potential bTB disease and improve the herd environment.

This study aims to explore micrometeorological influences on particle growth by the experimental and statistical approaches. Characteristic meteorological conditions of the nucleation event were observed, and turbulence in the PBL seemed to play a role in particle growth. The major micrometeorological factors governing particle size growth in the PBL were instability (-z/L), friction velocity (u*), Bowen ration (B), and downward shortwave radiation (RsDN) as determined by a regression model. This result indicates that the geographical properties including land surface cover and geomorphology have strong influence on the aerosol size growth in PBL.