Avian Mycobacteriosis: Risk Factors
and Reservoirs

Avian mycobacteriosis presents one of the most difficult management challenges for captive bird populations and recovery programs. Although not very many birds are lost to avian tuberculosis, each case presents a major management problem because of the difficulty determining how far the disease has spread in the collection. All enclosuremates and contacts of affected birds must be considered disease suspects until proven otherwise.

Unfortunately, there are no good diagnostic tests for avian tuberculosis in live birds and the disease cannot be treated, so these enclosuremates and contacts remain suspects for extended periods of time. This means that their enclosures are placed under quarantine, which significantly hinders captive population management. To address this problem, the Wildlife Disease Laboratories' Molecular Diagnostics Laboratory at CRES is conducting molecular strain typing on all of the isolates of Mycobacterium avium that have been obtained over the past few years.

In addition, the Wildlife Disease Laboratories' Clinical and Pathology laboratories are contributing to the extensive prospective data collection required for this study. Researchers hope to determine how many strains of Mycobacterium avium are circulating in the Zoological Society of San Diego's living collections, and to clarify the importance of bird-to-bird transmission versus acquisition of infection from the environment. This will enable staff to better focus disease control efforts and determine how often new strains of Mycobacterium avium are introduced into the Zoological Society's collection, which will help direct biosecurity and prevention efforts. Finally, this project will answer key questions about risk factors for transmission of the agent, which will allow management efforts to be more effectively focused on interrupting transmission.