Abstract

Between 2009 and 2010, in cyprinid farms located in Iasi and on the Prut River, we diagnosed several infections with bacterial strains, characteristic of mobile species ofAeromonas, and it developed as a result of the stress induced by biotic and abiotic factors. Several anamnetic investigations were carried out, as well as morpho-pathological and bacteriological investigations of two-summer-old phytophagous and common carp, from the fish farm of Larga-Jijia and of common carp captured from the Prut River. In order to identify the main factors favouring and determining fish disease and death losses. Samples were collected from the following species: common carp(Cyprinus carpio), silver carp (Hypophthalmichtys molitrix), and bighead carp (Aristichtys nobilis) from the fish farm as well as from the Prut River. In this respect, 38 fish were examined, all of them showing red ulcers, circumscribed by whitish rings, fragmentation of their dorsal fin and hemorrhagic diathesis. Necropsy examination of the abdominal cavity indicated the presence of a serious, sometimes serohaemorrhagic fluid, the adherence of the viscerae to the peritoneal walls, catarrhal enteritis, pale, fragile liver, with small dark red foci. All the strains that were tested showed mobility and oxidase-positivity, but they reacted differently to the other tests. Consequently, they were taxonomically grouped into the following species: Aeromonas hydrophila, Aeromonas caviae, andAeromonas sobria. Histological examination of skin fragments from ulcerated areas, as a result of an epidermal necrosis, showed a hyperplasia of the mucus secreting cells. In the liver, as a result of a hydric dystrophy, several haemorrhagic foci were identified. The intestinal walls were the main location for an inflammatory hyperplasia.

Key words: Cyprinids, Aeromonas, scanning electron microscopy (SEM), lesions.