Oral immunization of rainbow trout, Salmo gairdneri Richardson, against vibriosis with vaccines protected against digestive degradation

Abstract. In order to reduce digestive degradation of vaccines against vibriosis when administered orally to fish, two methods of protecting the antigens were tested. Lyophilized vaccine was either incorporated into a slow-release pellet or coated by an acid-resistant film. These vaccines were compared to both oral vaccination by an unprotected vaccine as well as to standard vaccination methods of immersion and injection. However, mortalities after an artificial challenge showed that the efficacy of the protected vaccines was lower than that of the unprotected vaccine given orally and the standard vaccination procedures. The reason for this is probably that the important antigens of vibriosis vaccines are lipopolysaccharides which are little affected by gastric digestion, and the coating of the vaccine or incorporation into slow-release pellets resulted only in reduced absorption of the antigens.     

Protection against enteric redmouth disease in rainbow trout, Salmo gairdneri Richardson, after vaccination with Yersinia ruckeri bacterin

Abstract. Rainbow trout, Salmo gairdneri Richardson, (average weight 100g) were vaccinated intraperitoneally (i.p.) with Yersinia ruckeri bacterin in saline or in oily adjuvant. Agglutinating antibody kinetics were followed during 445 days before challenge (1.2×10⁷ bacteria i.p.). Fourteen days after challenge 88.5% of the control fish had died while few mortalities were observed with vaccinated fish regardless of their agglutinating titre. Protection against Y. ruckeri does not seem to be due to antibodies.     

Bath-immunization—a practical and non-stressing method of vaccinating sea farmed rainbow trout Salmo gairdneri Richardson against vibriosis

Abstract. A non-stressing easily applicable vaccination method against vibriosis in rainbow trout is described. The vaccine consisted of trypsin digested Vibrio anguillarum cells and was administered through a 2 h bath treatment, giving adequate protection in challenge experiments with the same V. anguillarum strain.     

Strawberry disease in rainbow trout, Salmo gairdneri Richardson

Abstract. Strawberry disease is a subchronic, non–debilitating, and non–fatal inflammatory skin disease of rainbow trout that has been recognized for the past 25 years. Morbidity ranges up to 80% and the disease affects fishes from 15cm in length to brood stock size. Epizootiological data indicate that strawberry disease usually appears, first in the autumn and reaches peak incidence during the following winter and spring. Data also indicate that the disease is found only in certain trout farms in the western and Pacific north–western regions of the United States. Although the cause of strawberry disease is unknown, the normal clinical course of 8 weeks can be reduced by oral treatment with oxytetracycline. Clinical signs include appearance of bright red, raised, circumscribed, ulcerated and indurated lesions in the skin that usually range up to 3 cm or more in diameter. Microscopically, the disease is characterized as a subchronic, focal, non–suppurative dermatitis with ulceration and extensive infiltration of mononuclear inflammatory cells.     

The effects of the use of potassium alum adjuvant in vaccines against vibriosis in rainbow trout, Salmo gairdneri Richardson

Abstract. A formalized bacterin of Vibrio anguillarum , with and without alum adjuvant, was administered intraperitoneally to rainbow trout under farm conditions. Compared with the normal bacterin the adjuvanted preparation caused pathological changes indicative of chronic peritonitis, substantial early mortalities in 3 cm fish, and to a lesser extent in 20 cm fish, and depressed growth rate. No additional degree of protection against artificial challenge was obtained from its use.     

Immunoglobulin heterogeneity in the rainbow trout, Salmo gairdneri Richardson

Abstract. Hetereogeneity of rainbow trout immunoglobulins was demonstrated by using monoclonal antibody 1A6 and polyacrylamide-gradient gel electrophoresis. Immunoglobulins defined by elisa using monoclonal antibody 1A6 were about 30% of the total immunoglobulins, detected by elisa using polyclonal antibodies, in healthy rainbow trout. In trout obtained from farms with a previous history of infectious viral diseases, 1A6-immunoglobulins were only about 14% of the total. Several serum pools from infected trout could be totally depleted of 1A6-immunoglobulins (about 12% of total immunoglobulins) by affinity chromatography over Sepharose immobilized monoclonal antibody 1A6. Polyacrylamide-gradient gel electrophoresis under denaturing conditions of total immunoglobulins, 1A6 immunoglobulins and no-1A6 immunoglobulins purified by affinity chromatography, showed a majority heavy chain of 70 KDa and a minority heavy chain of about 60 KDa, two light chains of 24 and 26 KDa, and a 11–14 KDa polypeptide.     

Behaviour of rainbow trout, Salmo gairdneri Richardson, in marine cages

Abstract. Underwater television was used to observe the distribution and swimming behaviour of groups of farmed rainbow trout, Salmo gairdneri Richardson, in marine net cages. Undisturbed rainbow trout (mean total length 240 mm) aggregated near the surface, remaining motionless in slack water and formed polarized shoals at higher current velocities. Larger fish (mean total length 317 mm) occupied deeper parts of the cage and were more active during periods of slack water. The results are compared with previous work on farmed Atlantic salmon, Salmo salar L., and discussed in relation to the biology of wild rainbow trout and recent work on exercise, growth and condition in salmonids.     

Immunization of rainbow trout, Salmo gairdneri Richardson, against vibriosis: comparison of an extract antigen with whole cell bacterins by oral and intraperitoneal routes

Abstract. An extract vaccine against Vibrio anguillarum was compared with other vaccine preparations when administered to rainbow trout intraperitoneally or orally on food. Intraperitoneal vaccination resulted in virtually 100% protection within two weeks whereas oral vaccination gave a maximum protection of 50–70% after eight weeks. When administered intraperitoneally the extract performed better than formalin killed cells but when administered orally formalin killed cells were better. The addition of alum as adjuvant enhanced the response to antigen administered by both routes. Serum agglutinin litres after oral vaccination were low and variable but after intraperitoneal injection they reached a consistent peak of 64. As the response to oral vaccination was so low it was not possible to relate agglutinin titre to protection in a quantitative relationship.     

Phagocytic cells in the epidermis of rainbow trout, Salmo gairdneri Richardson

Abstract. Electron microscopical observations of skin of rainbow trout revealed the presence of several types of phagocytic cells in the epidermis, most notably macrophages, some of which were seen crossing the basal lamina. Occasionally, filament-containing cells showed either melanin granules or phagosomes, suggesting these cells were also capable of phagocytosis. No cells with the characteristics of the Langerhans cells were observed, which does not necessarily preclude the possibility of macrophages being able to play an identical role as antigen-trapping cells.     

Lysozyme from rainbow trout, Salmo gairdneri Richardson, as an antibacterial agent against fish pathogens

Abstract. The antibacterial effect of two lysozyme variants purified from rainbow trout, Salmo gairdneri Richardson, kidney was investigated as part of a project directed towards increasing the disease resistance of fish by the transgenic technique. Seven bacterial strains from five Gram-negative species, of which one was considered non-pathogenic, were examined. One of the rainbow trout lysozymes was surprisingly potent, having substantial antibacterial activity on all strains tested. Hen egg-white lysozyme was bactericidal only against the one species considered non-pathogenic. The data suggest that lysozyme does play a role in the disease defence of rainbow trout and that the gene for the most active lysozyme may be suitable for testing the transgenic strategy.     

Solid waste production from rainbow trout, Salmo gairdneri Richardson, cage culture

Abstract. There is increasing concern over the environmental impact of freshwater cage culture, but there is a lack of information on the amounts and nature of the wastes produced. This study presents measurements of the total solid waste arid solid carbon, nitrogen and phosphorus loadings from five Scottish rainbow trout, Salmo gairdneri Richardson, cage farms, and shows a significant input of solids below the cages. The results indicate a considerable variability in solid output which was partly due to variations in the feeding rate of fish with the cages, but was also thought to be due to variations in management on individual farms. The results compare well with other studies on land-based pond and tank systems and provide useful estimates of solid waste loadings for the prediction of environmental impact.     

Immunization of rainbow trout, Salmo gairdneri Richardson, against bacterial kidney disease: preliminary efficacy evaluation

Abstract. A bacterin for immunization against bacterial kidney disease of salmonid fishes caused by Renibacterium salmoninarum is described. Cultures were grown in Evelyn's KDM2 medium containing 10% calf serum in a fermenter under the following conditions: pH 7.2, 15°C, 800ml/min air, 200 rev/min agitation and 5–15 days of incubation. Possible substitutes for calf serum were 10% horse serum 0.15% starch and leptospira medium. The bacterins were inactivated with 0.3% formalin and no adjuvants were used. Other tests evaluated pH-lysed bacterin, 50% concentrated bacterin and 50% concentrated pH-lysed bacterin. Juvenile rainbow trout, salmo gairdneri Richardson, were vaccinated either by intraperiotoneal (i.p.) injection, 2 min immersion or 2-step hyperosmotic infiltration. Fish were held from four to six weeks at 11°C, then challenged by i.p. injection with the homologous virulent bacterium. Fish died from days 19 to 40 after challenge. The best preparation was pH-lysed bacterin given by a single i.p. injection; hyperosmotic and immersion vaccination were not effective. Typically when 80% or more of unvaccinated controls were infected as detected by Gram stain, 10% or less of the vaccinated fish were infected.     

The pathology of chronic ammonia toxicity in rainbow trout, Salmo gairdneri Richardson

Abstract. Two groups of rainbow trout fingerlings were exposed for 90 days to 0.2 and 0.4 mg/1 of un-ionized ammonia, respectively. Several fish exposed to the higher concentration soon developed clinical signs suggestive of a neurological dysfunction but subsequently recovered. No lesion attributable to ammonia was seen in the gills of any of the fish. This raises questions about the precise role of ammonia in the production of gill diseases in intensively cultured trout.