Molecular epidemiology of Mycobacterium avium subsp. avium and Mycobacterium intracellulare in captive birds

Mycobacterium avium subsp. avium and Mycobacterium intracellulare are primary causes of mycobacteriosis in captive birds throughout the world, but little is known about how they are transmitted. To define the local epidemiology of infection, we strain-typed 70 M. avium subsp. avium and 15 M. intracellulare culture isolates obtained over a 4-year period from captive birds. Typing was performed using randomly amplified polymorphic DNA (RAPD) PCR, amplified fragment length polymorphic (AFLP) fragment analyses, and for a subset of isolates, DNA sequencing of a segment of the 16S-23S rRNA internal transcribed spacer region. Six strain clusters comprising 43 M. avium subsp. avium, isolates were identified; 42 isolates had unique typing patterns, including all M. intracellulare isolates. Phylo-geographical analyses using RAPD and AFLP fingerprints and animal confinement histories showed no correlation between housing of infected birds and mycobacterial strain-type, except for two animals. The diversity of M. avium subsp. avium and M. intracellulare isolates and minimal evidence for bird-to-bird transmission suggest that environmental reservoirs may be important sources of infection in captivity.