Gross and Microscopical Findings
Overall, the fish were emaciated, thin and had scarce adipose tissue.
The information regarding the sex, size and weight, as well as gross and
microscopic lesions detected, are summarized in Table 1. Five fish were
revealed to have round or irregularly-round black areas on integument
and fins ranging from 2 to 5 mm in size. In addition, four fish showed
white or pinkish nodules on the skin, fins and/or oral mucosa (Figure
1). In one fish (case 9), white-yellowish multifocal nodules interpreted
as granulomas were observed in the spleen and perivisceral adipose
tissue. Through histological analysis, the spleen of six fish showed
multifocal, coalescent epithelioid granulomas with occasional central
necrosis and concurrent hyperplasia of melanomacrophagic centers (MMC).
In case 9, the spleen showed acid-fast bacteria within granulomas
(Figure 2). In other cases, including 1, 2, 5, 6, and 11, the granulomas
were Zeehl-Neelsen negative. All granulomas All granulomas contained
Gram positive granular material consistent with bacteria.
The cutaneous nodules histologically were consistent with the presence
of mature granulation tissue and concurrent mild, chronic, lymphocytic
dermatitis; signs of hypertrophy of fibroblasts, suggestive of an LCDV
infection, were absent. The black areas of the skin matched with focal
hypermelanosis and were not associated with intralesional parasites.