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Un estudio realizado a truchas, procedente del Lago Titicaca-Puno determinó la enfermedad flavobacteriosis y una mortalidad aproximadamente del 60%, posiblemente corresponda a Flavobacterium psychrophilum, conocido como el agente que causa la “enfermedad bactérica de aguas frías” (BCWD) o enfermedad del pedúnculo. La lesión macroscópica externa más frecuente fue la ulceración semejante a “sellos” de la región dorsal del pez, hemorragia ocular, erosión extensiva de la cola, con pérdida del tejido dérmico, anemia branquial, hipertrofia e hiperplasia. Internamente se observó una marcada esplenomegalia, hemorragia y zonas pálidas del hígado, inflamación del riñón, del intestino y acumulación de líquido ascítico en el peritoneo. La bacteria se aisló en TSA, presentó pigmentos amarillos y dio positivo con la oxidasa.

Graphical abstract, Flavobacterial diseases in fish are caused by multiple bacterial species within the family Flavobacteriaceae and are responsible for devastating losses in wild and farmed fish stocks around the world. In addition to directly imposing negative economic and ecological effects, flavobacterial disease outbreaks are also notoriously difficult to prevent and control despite nearly 100 years of scientific research. The emergence of recent reports linking previously uncharacterized flavobacteria to systemic infections and mortality events in fish stocks of Europe, South America, Asia, Africa, and North America is also of major concern and has highlighted some of the difficulties surrounding the diagnosis and chemotherapeutic treatment of flavobacterial fish diseases. Herein, we provide a review of the literature that focuses on Flavobacterium and Chryseobacterium spp. and emphasizes those associated with fish.

International audience; Bacterial cold water disease (BCWD) and rainbow trout fry syndrome (RTFS) caused by Flavobacterium psychrophilum are 2 of the major diseases causing high fish mortality in salmonid fish farms. The molecular epidemiology of F. psychrophilum is still largely unknown. Multilocus sequence typing (MLST) has been previously used for this pathogen and underscored a correlation between clonal complexes and host fish species. Here we used MLST to study the relationships among 112 F. psychrophilum isolates from rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta fario and S. t. lacustris in Swiss fish farms between 1993 and 2012. The isolates belonged to 27 different sequence types (STs). Most of the Swiss outbreaks were associated with strains belonging to clonal complexes CC-ST2 and CC-ST90, found in both rainbow trout and brown trout and represented by several STs. Eight ST singletons could not be connected to any known clonal complex. Already reported from other parts of Europe and North America, CC-ST2 was the most frequent clonal complex observed, and it caused the majority of outbreaks in Switzerland, with CC-ST90 being the second most important type. In the tightly interconnected Swiss fish farms, no association between clonal complex and host fish was detected, but a temporal evolution of the frequency of some STs was observed. The occurrence of sporadic STs suggests high F. psychrophilum diversity and may reflect the presence of different sequence types in the environment.

Flavobacteriosis are emerging infectious diseases in marine fish aquaculture, above all in the Mediterranean basin, characterized by cutaneous ulcers and erosions with cachexia and delayed growth, rarely lethal for the affected specimens. Among marine fish species, seabream and seabass are the most sensitive to the infection and recently also common dentex farmed in Sardinia. Authors describe the features characterizing a spontaneous outbreak occurred in a Sicilian off-shore farm of common dentex (Dentex dentex). On February 2003 infected specimens were sampled and microbiological and histopathological assays were performed. Cutaneous changes of diseased specimens were erosions with depigmentation and/or haemorrhages, ulcers deepened beneath the musculature, fin and caudal erosions. By the histological point of view, subcutaneous tissue was characterized by necrosis, parvicellular infiltration and several filamentous bacteria. Extent of focus and severity of symptoms confirmed the dangerous potential of flavobacterial infections for the Mediterranean mariculture and a limiting factor in common dentex farming development.