Gokulraj, A.; Praveenraj, J.; Gnanadesikan, R., and Arumugam, U., 2019. Mycobacterial infection in ornamental fishes farmed in low saline waters of Tiruvallur District, India. In: Jithendran, K.P.; Saraswathy, R.; Balasubramanian, C.P.; Kumaraguru Vasagam, K.P.; Jayasankar, V.; Raghavan, R.; Alavandi, S.V., and Vijayan, K.K. (eds.), BRAQCON 2019: World Brackishwater Aquaculture Conference. Journal of Coastal Research, Special Issue No. 86, pp. 134–137. Coconut Creek (Florida), ISSN 0749-0208.
The present study reports the detection of Mycobacterium sp. infection in the ornamental fish, Carassius auratus (Gold fish) and two exotic cichlid fishes, Andinoacara rivulatus (Green terror cichlid) and Thorichthys meeki (Fire mouth cichlid) cultured in the low saline waters (5 ppt) of Tiruvallur district. The infected gold fish demonstrated symptoms of skin ulceration, frayed fins, pale gills, disorientation in swimming, ascites and nodules in the liver, whereas the cichlid fishes possessed severe emaciation, skeletal deformity, blackening, weakness and ulceration. The pathogen was isolated in Middlebrook 7H9 broth as typical pink colonies characteristic of Mycobacterium sp. PCR sequencing of the HSP gene was done for molecular confirmation, and the sequences generated were submitted in the GenBank under the accession numbers MK424614, MK424615 and MK424616. Histopathological observation of the organs of the infected fishes revealed granuloma, neutrophil infiltration and vacuolisation in heart, liver and brain. Histopathological changes typical of Mycobacterium sp. viz., lamellar disorientation, and neutrophil infiltrations in the heart, inflammation and congestion in the liver, granuloma in the kidney were documented in infected cichlids. The detection and confirmation of mycobacteriosis in the ornamental fishes cultured in low saline waters of Tamil Nadu is the first report and alert the fish handlers to undertake precautionary measures to prevent the transmission of mycobacterium infection from fish to fish handlers.