Mycobacteriosis in Zebrafish Colonies

Christopher M. Whipps, Christine Lieggi, and Robert Wagner

Christopher M. Whipps, PhD, is an assistant professor in the Department of Environmental and Forest Biology, State University of New York College of Environmental Science and Forestry in Syracuse, New York. Christine Lieggi, DVM, DACLAM, is the associate director and head of veterinary services at the Research Animal Resource Center, Memorial Sloan-Kettering Cancer Center and Weill Cornell Medical College in New York, New York. Robert Wagner, VMD, Dipl. ABVP-ECM, is the chief of surgical veterinary services and associate professor in the Division of Laboratory Animal Medicine, University of Pittsburgh, Pennsylvania.

Address correspondence and reprint requests to Dr. Christopher M. Whipps, State University of New York College of Environmental Science and Forestry, Environmental and Forest Biology, 1 Forestry Drive, Syracuse, NY 13210 or email cwhipps@esf.edu.

Abstract

Mycobacteriosis, a chronic bacterial infection, has been associated with severe losses in some zebrafish facilities and low-level mortalities and unknown impacts in others. The occurrence of at least six different described species (Mycobacterium abscessusM. chelonaeM. fortuitumM. haemophilumM. marinumM. peregrinum) from zebrafish complicates diagnosis and control because each species is unique. As a generalization, mycobacteria are often considered opportunists, but M. haemophilum and M. marinum appear to be more virulent. Background genetics of zebrafish and environmental conditions influence the susceptibility of fish and progression of disease, emphasizing the importance of regular monitoring and good husbandry practices. A combined approach to diagnostics is ultimately the most informative, with histology as a first-level screen, polymerase chain reaction for rapid detection and species identification, and culture for strain differentiation. Occurrence of identical strains of Mycobacterium in both fish and biofilms in zebrafish systems suggests transmission can occur when fish feed on infected tissues or tank detritus containing mycobacteria. Within a facility, good husbandry practices and sentinel programs are essential for minimizing the impacts of mycobacteria. In addition, quarantine and screening of animals coming into a facility is important for eliminating the introduction of the more severe pathogens. Elimination of mycobacteria from an aquatic system is likely not feasible because these species readily establish biofilms on surfaces even in extremely low nutrient conditions. Risks associated with each commonly encountered species need to be identified and informed management plans developed. Basic research on the growth characteristics, disinfection, and pathogenesis of zebrafish mycobacteria is critical moving forward.

Key Words: biofilms; disinfection; mycobacteriosis; Mycobacterium chelonaeMycobacterium haemophilumMycobacterium marinum; surveillance; zebrafish

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