Surveillance of health status on eight marine rainbow trout, Oncorhynchus mykiss (Walbaum), farms in Denmark in 2006

Abstract

The health status of eight marine rainbow trout farms was followed from mid-June to mid-September 2006 by sampling both dead and healthy fish approximately every 2 weeks for bacteriological and virological investigation. No fish pathogenic viruses were detected, but all farms experienced disease and mortality as a result of various bacterial infections. Yersinia ruckeri was found on four and Renibacterium salmoninarum on five of the farms, but only during the first part of the surveillance period. This indicates that the fish carried the infection from fresh water, and cleared the infection in salt water. Aeromonas salmonicida subsp. salmonicida caused mortality on five farms, but persisted throughout the sampling period. Although A. salmonicida was probably carried from fresh water, the fish were not able to clear the infection in the sea. Vibrio anguillarum caused mortality on six of the farms throughout the sampling period, O1 being the dominant serovar, and Photobacterium damselae subsp. damselae was found on seven farms as a cause of disease. During the period of highest water temperatures Vibrio parahaemolyticus and Vibrio vulnificus were detected in dead fish in five and two farms, respectively, although their significance as causative pathogens is questionable. Vibrio vulnificus has not previously been found in rainbow trout in Denmark. Both mortality and number of antimicrobial treatments during the period were considerably higher in unvaccinated compared with vaccinated fish. Resistance to commonly used antimicrobials was low or absent.

The Fish Pathogen Vibrio vulnificus Biotype 2: Epidemiology, Phylogeny, and Virulence Factors Involved in Warm-Water Vibriosis

“…Afterwards, the disease was reported in different European eel farms, including those from Nordic countries (notably Germany, Holland, and Denmark) (30, 31; and personal communications with different eel farmers). In parallel, new warm-water vibriosis cases, which affected other farmed fish species and shrimps were reported worldwide (21,22,23,24). None of these cases caused the detrimental effects that warm-water vibriosis produced on eel aquaculture (personal communications with different eel farmers).…”

“…The most susceptible host for this vibriosis is the eel (Anguilla anguilla and A. japonica) (20). Other susceptible hosts are derbio (Trachinotus ovatus) (21), tilapia (Oreochromis sp) (22), trout (Oncorhynchus mykiss) (23), and shrimp (Penaeus vannamei) (24). Warm-water vibriosis in its acute form is also a primary septicemia, but in this case, it is triggered irrespectively of the pathogen's route of entry (gills, intestine, skin injury) and/or the host's immune status (25).…”

Insights into the antibacterial and immunomodulatory functions of the antimicrobial peptide, epinecidin-1, against Vibrio vulnificus infection in zebrafish

“…V. vulnificus causes septicemia with an average mortality rate exceeding 50% in humans [3,4]. However, on aquaculture farms during the period of highest water temperatures, Vibrio parahaemolyticus and V. vulnificus were respectively detected in dead fish from five and two farms in Denmark in 2006 [5]. Vibrio infections are sequelae related to environmental stress or other disease processes in shrimp and frequently cause shrimp death [6].…”

Identification of Aeromonas salmonicida in European perch from North Lithuanian rivers during mass mortalities in 2008

“…Bacterial pathogens cause mortality, especially of cultured fish but occasionally of wild fish as well [5][6][7][8]. Bacterial pathogens of fish form a diverse group and are mainly represented by Gram-negative bacteria.…”