Massive infection of Cystidicoloides ephemeridarum in brown trout Salmo trutta with skeletal deformities.

We investigated the cause of skeletal deformities found in brown trout from the Aspromonte mountain area in Reggio Calabria, Italy. Toxicological, histopathological and parasitological analyses were carried out on 14 fish with evident macro-morphological alterations from 2 different locations in the same river, and 4 control fish without morphological alterations from a different river (far from the first river but still within the area under study). Histopathological and radiological observations confirmed severe skeletal deformities in the specimens investigated. Parasitological examinations highlighted the presence of the nematode Cystidicoloides ephemeridarum, found only within the gastrointestinal tract of specimens showing deformities. Moreover, a direct correlation between parasite number and fish size was found. Given the low heavy metal levels and the presence of a massive parasitosis in teleosts showing deformities, we postulate a correlation between skeletal deformities and nematode infestation: the parasites caused a serious vitamin and mineral deficiency in the fish, which led to a dysplastic vertebral column. The low calcium levels found in malformed specimens compared with negative controls effectively confirm this hypothesis.

Gastric leiomyoma in a sea bass Dicentrarchus labrax broodfish.

This report describes a spontaneously arising non-infiltrative neoplasm of gastric tunica muscularis in a broodstock sea bass Dicentrarchus labrax from an Italian aquaculture farm. Microscopically, the mass was circumscribed and non-encapsulated and was composed of spindle cells arranged in parallel interlacing bundles or, occasionally, a whirling pattern. Cells had a small quantity of eosinophilic cytoplasm with distinct cell borders. Neoplastic cells were immuno-reactive with smooth muscle actin, vimentin and desmin; S100 was negative. The mucosal epithelium was intact with no neoplastic involvement. A gastric leiomyoma was diagnosed based on the findings. More efforts should be made to study the possible etiology of leiomyoma affecting fish from aquaculture.

Squamous cell carcinoma in a wild European bullhead Cottus gobio.

A pharyngeal tumor was found in a wild European bullhead. The tumor mass appeared underneath the operculum and was bilobed. The major neoplastic component showed diffuse epithelial squamous differentiation. Crossmonn's trichrome allowed identification of connective tissues whereas no neoplastic cells were stained. Periodic acid-Schiff was negative within the mass, and Giemsa did not show any further diagnostic significance. Immunohistochemistry showed diffuse positive cytoplasmic staining of the neoplastic population with an anti-human pancytokeratin antibody. Vimentin was negative and exclusively stained the stroma. On the basis of the morphological and immunohistochemical results, a squamous cell carcinoma was diagnosed.