Summary
Cichlids include several fish species having a high economic value in
the field of aquaculture. The ornamental fish export trade is mostly
based on fish from the african Lake Malawi. Despite their huge economic
importance, management of ornamental fisheries is challenged by a
paucity of information on the status of the exploited fish stock. The
possibility of guaranteeing healthy animals is of paramount importance
and has several implications, both for commercial and sanitary reasons.
Grossly, cutaneous nodules and black spots are pathological findings
frequently encountered in fish, suggesting a meandering disease without
a specific etiologic association. Ornamental fish species are plagued by
mycobacteriosis, which is quite classically associated with granulomas.
This work focuses on debilitated ornamental cichlids presenting
cutaneous nodules and black spots and sampled during routinary managing
activities held in an aquarium commercial facility; the fish underwent
pathological analysis and the presence of pathogens was investigated
through a molecular approach. In particular, the presence of
lymphocystis disease virus (LCDV), typically associated
with cutaneous nodular disease,
was excluded.Histologically the granulomas were localized in the spleen,
sometimes extending to the other visceral organs. Bacterial Heat-Shock
Protein 65 PCR products were detected in tissues associated to
granulomas and molecular investigation identified Mycobacteriumspp. in two samples and Cutibacterium acnes in seven samples.
Variably sized round “Hamazaki-Wesenberg-like” bodies were
immunolabeled with C. acnes antibody within macrophages forming
the granuloma in the spleen. C. acnes has been recently detected
by Next Generation Sequencing in the microbiome of internal organs of
fish. The role of C. acnes within internal fish tissues deserves
attention; its role as potential granulomatogenous agent, is taken in
consideration.