Conditions relevant to the occurrence of acid-fast bacilli in sphagnum vegetation

Biotopes with intact sphagnum vegetation were studied in Naustdal, West Norway: the health district with the former highest leprosy incidence rates in Norway. Concentration of acid-fast bacilli and concentration of non-cultivable acid-fast bacilli found in the vegetation fluid were compared with a series of variables related to the local environment and to the samples of vegetation. In bivariate analyses high concentrations were found in biotopes with orientation toward South, with a high coverage of vascular plants and with presence of Ericaceae. High concentrations were also found where dry weight of a vegetation was high, where pH in the fluid was low and where dry weight of the fluid was high. In a multivariate analysis, log-linear model, based on concentration of acid-fast bacilli as the dependent variable and orientation, pH, dry weight of vegetation and dry weight of fluid as the independent variables, all two-factor effects including the dependent variable were retained in the model. Furthermore, orientation versus dry weight of vegetation and dry weight of fluid versus dry weight of vegetation were retained.