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Oral immunization for possible control of furunculosis in fish

This project was initiated in an attempt to control furunculosis (Aeromonas salmonicida) in a production hatchery rearing coho salmon. An oral vaccine was prepared and administered to 520,000 juvenile coho salmon (Oncorhynchus kisutch) at the Siletz River Salmon Hatchery prior to the onset of a predictable naturally occurring epizootic of furunculosis. A group of 65,000 salmon served as a nonimmunized control. The Fermacell Fermentor was used to grow the Aeromonas salmonicida cells. The cell yield was more than doubled with the addition of 175 grams of dextrose to the culture media accompanied by automatic control of the pH. The cells were subjected to ultrasonic disruption and the supernatant fluid was precipitated with alum. The resulting material was lyophilized and incorporated into the Oregon Moist Pellet diet at a concentration of 201.73 milligrams ± 3 milligrams per kilogram of pellets. Immunization with vaccine-containing food was begun on March 26, 1967 with 14 consecutive days of initial vaccination followed by eight weekly boosters. It was calculated that each fish could receive approximately 360.7 micrograms of vaccine during the immunization period. During the period of May 1 through July 12, 1967, all hatchery mortalities were collected and examined for the presence of Aeromonas salmonicida. Although the nonimmunized control group showed a higher total loss and a higher furunculosis loss than the immunized groups, the results fail to indicate any distinctive difference between these two lots. The lower mortalities observed in the immunized group may indicate that slight immunity had been induced by the vaccine. However, any low-level immunity which may have been produced was not sufficient to provide protection against infection by Aeromonas salmonicida. The number of mortalities appeared to be closely associated with the hatchery water temperature. An increase in water temperature was accompanied by a corresponding increase in losses. A decline in losses appeared to be associated with a decrease in water temperature. Of the fish examined, 146 animals showed the presence of an acid-fast organism tentatively identified as Mycobacterium fortuitum (Cruz). Agglutinating antibody titers on serum samples from the immunized and nonimmunized groups of fish failed to indicate any meaningful difference between these groups.
Oregon State University
Coho salmon
Masters Thesis
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Fryer, J. L.
Oregon State University. Graduate School
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Oral immunization for possible control of furunculosis in fish
Frost, Gary Douglas
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