Yersiniosis outbreak in rainbow trout (Oncorhynchus mykis) at a fish farm from Northern Romania

Abstract

Yersiniosis (Enteric diseases – red mouth) is a septicemic infectocontagious disease of salmonides, produced by Yersinia ruckeri, young rainbow trout being the most susceptible to infection. The disease appears as an exogenous or endogenous infection, influenced by favouring factors. The infection sources are represented by sick and asymptomatic carrier fishes that eliminate Yersinia through faeces, contaminating water and fodder. At the beginning of the disease outbreak, which is the subject of the present scientific paper, sudden water warming (15-17ºC) in the spring of 2008 was incriminated. The bacteriological examination carried out on the anterior kidney and heart blood from trout suspected of yersiniosis had as result the isolation of some Yersinia ruckeri bacteriological strains, confirming the suspected diagnosis, based on lesions (high degree anaemia of oral mucosa and branchia, haemorrhagia on tongue mucosa, exophthalmia and ocular haemorrhagia). The identification of the causative agent was based on morphological aspects (gramnegative, motile and rod-shaped) and distinctive metabolic characters, tested by using API galleries. Antibiogramas pointed out the Y. ruckeri strain susceptibility to Oxytetracicline, Flumequine, Trimethoprim and Ceftiofur and a medium susceptibility to Amoxicillin and Enrofloxacin.