1982 Volume 16 Issue 4 Pages 201-206
Efficacy of oral vaccination for control of streptococcal disease in cultured yellowtail was studied. The bacterin, the formalin-killed cells of Streptococcus sp., as the etiological agent of this disease, was used.
This bacterin was administrated 1, 2, 4, 8, 16 times at a level of 5 mg dry weight per fish per day, and 8, 12 times at a level of 20 mg wet weight per fish per day. About a week after the last vaccination, fish were challenged for the estimate of efficacy of oral vaccination. Duration of oral vaccination effect was also tested. Dry bacterin was fed 2, 4, 8 times, and about 1, 2, 3, 4 weeks after the first vaccination, fish were challenged for the estimate of oral vaccination effect.
Both dry and wet bacterin were effective, and the efficacy became more active with an increase in frequency of oral vaccination. But antibody in the blood was not detected. Duration of oral vaccination effect was very short. That effect was prolonged for only 2 weeks after the last vaccination.
In order to compare with oral vaccination, efficacies of hyperosmotic infiltration and intraperitoneal injection for control of this disease were also studied. Hyperosmotic infiltration was more effective than oral vaccination. Intraperitoneal injection was the best method of three experimented.