PCR analysis of the presence and location of Mycobacterium avium in a constructed reed bed, with implications for avian tuberculosis control.

The potential of reed beds to act as biofilters of pathogenic and environmental mycobacteria was investigated through examination of the fate of mycobacteria in a constructed reed bed filtering effluent from a large captive wildfowl collection. Particular emphasis was placed on the presence and location of Mycobacterium avium--the causal agent of avian tuberculosis (ATB)--in an effort to clarify the potential role of reed beds in the control of this disease. Water, sediment, and stems and roots of common reed (Phragmites australis) and greater reedmace (Typha latifolia) were taken from 15 locations within the reed bed plus sites upstream and downstream. Samples were analysed for mycobacteria using PCR and specifically for M. avium using nested PCR. Environmental mycobacteria were found throughout the entire reed bed but M. avium was not found downstream of the first vegetation growth. The reed bed was found to effectively remove M. avium from the water through a combination of sedimentation and adsorption onto vegetation stems. The results of this study show that constructed reed beds composed of a settlement lagoon and one or more vegetation beds can act as valuable and ecologically friendly tools in the environmental control of ATB.