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Systemic Granulomatous Mycobacteriosis in Orbiculate Batfish (Platax orbicularis) Associated with Mycobacterium marinum-like Organism in an Aquarium in South Korea
1
Department of Companion Animal Health and Science, Silla University, Busan 46958, Republic of Korea
2
Department of Veterinary Clinical Pathology, College of Veterinary Medicine, Konkuk University, Seoul 05029, Republic of Korea
3
OSH Veterinary Clinic, Seoul 04733, Republic of Korea
*
Author to whom correspondence should be addressed.
Vet. Sci. 2026, 13(5), 489; https://doi.org/10.3390/vetsci13050489
Submission received: 21 April 2026
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Revised: 11 May 2026
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Accepted: 15 May 2026
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Published: 18 May 2026
Simple Summary
This report describes systemic granulomatous disease in an orbiculate batfish from an aquarium in South Korea. Gross and histopathological examinations revealed severe multifocal granulomas containing acid-fast bacteria across multiple organs, including the gills, spleen, and kidney. Subsequent molecular analysis showed that the detected bacterium was interpreted as being most closely related to Mycobacterium marinum. These findings highlight the need for continued monitoring of bacterial infections in aquarium fish and support awareness of potential zoonotic risks to handlers and aquarists.
Abstract
In this report, we describe systemic granulomatous mycobacteriosis in an orbiculate batfish from an aquarium in South Korea. Gross examination of the deceased fish showed multifocal nodular lesions in multiple internal organs including the gills, spleen, and kidney. Histopathological analysis demonstrated severe chronic systemic granulomatous inflammation, and Ziehl–Neelsen staining highlighted abundant intralesional acid-fast bacilli. Molecular analysis based on partial sequencing of the 16S ribosomal RNA (rRNA) and heat shock protein 65 (hsp65) genes showed that the detected organism was most closely related to Mycobacterium marinum. Because the molecular analysis was performed using partial sequences obtained from formalin-fixed, paraffin-embedded tissues, definitive species-level identification was not possible. This case represents systemic granulomatous mycobacteriosis associated with a Mycobacterium marinum-like organism in orbiculate batfish in an aquarium in South Korea and emphasizes the need for continuous disease surveillance and improved diagnostic awareness of non-tuberculous mycobacterial infections in ornamental and public aquarium fish.
