Red mouth disease in rainbow trout (Oncorhynchus mykiss) – a case report on lake trout farm from Bicaz, Romania.

Yersiniosis or red mouth disease is a contagious infectious disease of salmonids caused by the bacterium Yersinia ruckeri, which lead to significant economic losses in trout aquaculture worldwide. Sources of infection are the sick fish and asymptomatic carriers, which eliminates yersiniosis faeces, causing contamination of water and feed. Triggers the disease was in March, the surge in water temperature values of 15-170 C. The fish affected were the younger with low immune system, the sudden departure of the winter period. Histological examinations, immunohistochemical and bacteriological made from liver, spleen, kidney and blood of the trout heart yersiniosis suspects resulted in the identification of the species bacterium Yersinia ruckeri strain, confirming the suspected diagnosis based on clinical investigations (pronounced anemia of mouth and gills mucosa, dark color of skin, bleeding on the lingual mucosa, protruding eye bleeding). Bacteriological confirmation was done by identifying the causative agent, based on morphological characters (gram negative bacilli, mobile) and the distinctive biochemical characters tested using the API rapid tests. Histological examinations revealed colonies of bacteria in liver, spleen and kidneys were confirmed to be colonies of Yersinia ruckeri by immunohistochemistry with anti-Yersinia ruckeri. Antibiogram revealed sensitivity of Yersinia ruckeri at: Oxytetracycline, Flumequin, Trimethoprim and Ceftiofur, and moderate susceptibility to Amoxicillin and Enrofloxacin.