DAO 94:143-152 (2011)  -  DOI: https://doi.org/10.3354/dao02319

ABSTRACT: The objective of this study was to describe the frequency of histopathological lesions and categorize histopathologically evident infections in sick ornamental fish from pet shops in New South Wales, Australia. We examined 108 fish that had evidence of morbidity or mortality, including 67 cyprinids, 25 osphronemids, 11 poeciliids, 4 characids and 1 cichlid, sourced from 24 retail outlets. Conditions frequently observed in the study population included branchitis (62/86, 72.1%), visceral granulomas (41/108, 38.0%), dermatitis (17/55, 30.9%), wasting (31/108, 28.7%), and intestinal coccidiosis (18/104, 17.4%). Branchitis and dermatitis were usually due to monogenean flukes, or flagellate or ciliate protozoa. Intralesional Microsporidia (16/41, 39.0%), mycobacteria (7/41, 17.%), or Myxosporidia (5/41, 12.2%) were identified in the majority of fish with visceral granulomas; however, special stains were critical in their identification. The proportion of histologically evident infections was remarkably high (77/108, 71.3%), and parasitic infections predominated. Many pathogens ­identified in the study have low host specificity and/or direct life cycles which would facilitate transmission to exposed naïve fish populations, potentially posing a threat to native and commercial fish populations. Those caring for sick ornamental fish should take appropriate steps to investigate in­fectious disease and should take precautions that prevent the spread of pathogens.

KEY WORDS: Ornamental fish · Histopathology · Lesion · Parasite · Bacteria