FIRST OCCURRENCE OF ENTERIC REDMOUTH DISEASE (ERM) IN RAINBOW TROUT (Oncorhynchus mykiss)

Objective: The aims of this investigation were detection of causative agents and sources of infection agent as well as design of eliminate protocol for eradication of disease in the region. Method & Materials: Fish samples: Twenty five affected fish samples with weight average of 100-150 g that showed typical clinical signs were collected as source of infection for bacteriology investigation. Samples had been revealed some clinical signs such as lethargy, spiral swimming and had dark color, hemorrhages at base fins and vent, anal prolapse, reddening of maxilla and mandibullar areas, palate, gill operculum and eyes. Bacteriological examination: Suspected samples were collected from lower intestine, posterior kidney, spleen, liver, intestine, heart and stomach of moribund fish that revealed hemorrhages in the mouth and had swollen abdomen. Then it subcultured on general media. Results & Conclusion: Research findings revealed presence of Gram-negative stain, motile rods which had the following biochemical characteristics: negative cytochrome oxidase and urease; produced acid, alkaline slant but no gas from glucose; positive for ornithine and lysine decarboxylase but not arginine dihydrolase; and lack of H2S and gas production in triple sugar iron agar; fermentation of glucose and non fermentation of sucrose and lactose; non-utilization of rhamnose and arabinose; and lack of indole production; so the isolated bacteria was confirmed to be Yercinia ruckeri which had a positive agglutination with rabbit anti-K ruckeri serum. Recommendation protocol was issued as control and prevention measures to eliminate the adverse environmental factors and excessive stresses to reduce the disease occurrence.

کلیدواژه ها:

Enteric Redmouth Disease ، Rainbow trout ، propagation farms ، Iran