Progress 03/01/02 to 08/01/06
Outputs
In 1998, we identified V. carchariae as the causative agent of a disease outbreak on a summer flounder farm in Rhode Island. In a monitoring program of two summer flounder hatcheries, we discovered that V. harveyi can be a major component of the intestinal flora of larval and juvenile summer flounder in hatcheries. Survivors of FINE have a high proportion of sealed intestines and perform poorly. Potential sources of V. harveyi include water, and feed sources, such as algal cultures, rotifers, and artemia. Different strains of V. harveyi can be present at a single facility, as indicated by RAPD analysis. Presence of V. harveyi in summer flounder is not necessarily correlated with disease outbreaks. Histological signs indicative of FINE were only observed in juvenile fish, and significant mortalities were only observed after transport stress, both in challenge experiments and during the monitoring program. Infection risk is highest when fish are spawned in the spring and
summer, due to the presence of this pathogen in warm coastal waters. Other potential bacterial pathogens of summer flounder isolated from juvenile fish at a hatchery during the summer season included Photobacterium damselae and Vibrio ichthyonteri. No mortalities were associated with these two bacteria in the hatchery. Isolates of P. damselae and V. ichthyoenteri were not pathogenic to summer flounder when given by intraperitoneal injection. Two isolates of V. harveyi were pathogenic. We conclude that V. harveyi is an opportunistic pathogen of summer flounder and could have a major impact on development of summer flounder aquaculture.
Impacts
Flounder Infectious Necrotizing Enteritis (FINE) is a major constraint for the development of summer flounder aquaculture. Knowledge about the environmental conditions that trigger disease outbreaks gained in this research has been applied towards the development of an extension publication with recommendations for the prevention and management of FINE in summer flounder. These recommendations will result in enhanced production of summer flounder.
Publications
- Gauger E, Smolowitz R, Uhlinger K, Casey J, Gomez-Chiarri M. 2006. Vibrio harveyi and other bacterial pathogens in cultured summer flounder. Aquaculture 260:10-20.
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Progress 01/01/05 to 12/31/05
Outputs
Analysis of the data from a monitoring program of two summer flounder hatchery facilities showed that risk of infection with the bacterial pathogen Vibrio harveyi, causative agent of flounder, is highest when fish are spawned in the spring and summer seasons, most probably due to the presence of this ubiquitous pathogen in warm coastal waters. Major mortalities were associated with transport stress. Survivors of FINE outbreaks have a high proportion of sealed intestines and perform poorly. Other potential bacterial pathogens of summer flounder were isolated from juvenile fish at a hatchery during the summer season, including Photobacterium damselae damselae and Vibrio ichthyonteri. However, no major mortalities were associated with these two potential pathogens in the hatchery. Isolates of P. damselae damselae and V. ichthyoenteri were not pathogenic to summer flounder when administered by intraperitoneal injection, while two isolates of V. harveyi were shown to be
pathogenic. We conclude that V. harveyi is an opportunistic pathogen of summer flounder, and that it could have a major impact on the development of summer flounder aquaculture.
Impacts
Flounder Infectious Necrotizing Enteritis (FINE) is a major constraint for the development of summer flounder aquaculture. Knowledge about the environmental conditions that trigger disease outbreaks gained in this research has been applied towards the development of an extension publication with recommendations for the prevention and management of FINE in summer flounder (Paralichthys dentatus). These recommendations will result in enhanced production of summer flounder.
Publications
- No publications reported this period
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Progress 01/01/04 to 12/31/04
Outputs
A monitoring program for Vibrio harveyi and other potential bacterial pathogens in cultured juvenile summer flounder found that V. harveyi is a major threat to the summer flounder aquaculture industry and that incoming water was the likely source of V. harveyi. Also, dominant intestinal colonization with V. harveyi can be tolerated; however, transport stress or other environmental factors can trigger epizootics. Experimental infections were conducted to determine the effect of temperature, salinity, and transport on the virulence of Vibrio harveyi in juvenile summer flounder. Temperature was shown to have a significant effect on virulence in experimental infections and on proteolytic activity of V. harveyi culture supernatants. High temperature and transport were identified at two potential triggers of V. harveyi epizootics. The susceptibility to disease caused by Vibrio harveyi strain DN01, originally isolated from diseased summer flounder, was assessed for several
economically or environmentally important fish species in the Northeast US including tautog, black sea bass, Atlantic salmon, rainbow trout, and mummichog. The results of this study suggest that V. harveyi strain DN01, though well adapted to cause disease in summer flounder, does not pose as great of a threat to the other species tested. A mutant strain of Vibrio harveyi (SGM1) was created that was partially impaired in its ability to grow on a variety of media including media containing flounder intestinal mucus as a sole carbon source. This experimental condition also showed decreased protease activity. In experimental infections, the mutant was attenuated, however, it was not protective against subsequent exposure to the wild type.
Impacts
Knowledge about the environmental conditions that trigger disease outbreaks can be applied towards the prevention of Flounder Infectious Necrotizing Enteritis (FINE) in summer flounder (Paralichthys dentatus).
Publications
- No publications reported this period
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Progress 01/01/03 to 12/31/03
Outputs
In 1998, we identified V. carchariae as the causative agent of a disease outbreak in a summer flounder farm in Rhode Island. In a monitoring program of two summer flounder hatcheries, we discovered that V. harveyi can be a major component of the intestinal flora of larval and juvenile summer flounder in hatecheries. Potential sources of V. harveyi include water, and feed sources, such as algal cultures, rotifers, and artemia. Different strains of V. harveyi can be present at a single facility, as indicated by RAPD analysis. Although most of these strains can cause mortality of summer flounder by intraperitoneal injection, it is currently unknown if there are differences in their ability to colonize the intestine and cause disease in the farm. Presence of V. harveyi in summer flounder is not necessarily correlated with disease outbreaks. Histological signs indicative of FINE were only observed in juvenile fish, and significant mortalities were only observed after
transport stress, both in challenge experiments and during the monitoring program. Factors that could influence the occurrence of disease include: age of the fish, genetic susceptibility of the fish, strain of V. harveyi, previous exposure to the pathogen, environmental conditions, and the presence of competing bacterial strains.
Impacts
This work confirms that V. harveyi is a major pathogen of finfish and shellfish worldwide, and stresses the importance of vaccine development for this bacterial species.
Publications
- No publications reported this period
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Progress 01/01/02 to 12/31/02
Outputs
In 1998, we identified V. carchariae as the causative agent of a disease outbreak in a summer flounder farm in Rhode Island. With the goal of developing tools for the diagnosis and prevention of disease caused by V. carchariae in fish, we analyzed the biochemical profiles and 16S rDNA sequences of 17 bacterial isolates previously identified as V. harveyi, V. carchariae, and V. campbellii. These isolates have been responsible for disease and mortality in a wide variety of finfish and shellfish species worldwide, from oysters and seabass in Europe, to summer flounder in USA, and shrimp and grouper in Asia. 16S rDNA sequencing confirmed the homogeneity and synonymy of V. harveyi and V. carchariae. Analysis of biochemical profiles revealed that they are insufficient by themselves to differentiate V. harveyi/carchariae and V. campbellii strains. 16S rDNA sequencing, however, could be used in conjunction with biochemical techniques to provide a reliable means of
distinguishing V. harveyi/carchariae from other closely related species. We are currently in the process of developing mutants of V. harveyi unable to grow in intestinal mucus with the goal of identifying potential vaccine candidates for this ubiquitous bacterial pathogen
Impacts
This work confirms that V. harveyi is a major pathogen of finfish and shellfish worldwide, and stresses the importance of vaccine development for this bacterial species.
Publications
- Gauger EJ, Gomez-Chiarri M. 16S ribosomal DNA sequencing confirms the synonymy of Vibrio harveyi and V. carchariae. Dis Aquat Organ. 2002 Nov 7;52(1):39-46.
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