Abstract
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
Mycobacterium spp. 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.