Mycobacteriosis in the swim bladder caused by Mycobacterium fortuitum in a blood parrot cichlid (Amphilophus citrinellus × Paraneetroplus synspilus)

Abstract

Background

Swim bladder disorders occur frequently in several fish species, with bacterial infections being a primary cause. However, infections caused by mycobacteria are not usually reported.

Case description

A blood parrot cichlid (Amphilophus citrinellus × Paraneetroplus synspilus) presented with a recurrent unresponsive swim bladder disorder. The fish had undergone several unsuccessful aspirations of the swim bladder and antimicrobial treatments. Ultrasonography and radiography indicated fluid accumulation in the swim bladder. A turbid-yellowish fluid containing numerous acid-fast–positive bacilli was obtained during swim bladder aspiration. The fish was subsequently euthanized, and the necropsy revealed a fluid-filled enlarged swim bladder with yellowish sediments. Histopathological examination using Ziehl–Neelsen staining identified multiple granulomas encapsulating acid-fast–positive bacilli in several internal organs. Mycobacterium fortuitum infection was confirmed through polymerase chain reaction assay and genetic analysis.

Conclusion and case relevance

This primary report documents the unusual pathology of M. fortuitum infection in this particular cichlid species, in which the bacteria colonized the swim bladder cavity, leading to a buoyancy disorder.