A comparison was made on the efficiency of oral and hyperosmotic vaccinations for the control of vibriosis in ayu (Plecoglossus altivelis), the equal dose of vaccine being used.
1) The formalin-killed vaccine adsorbed to compound feed was administrated to 350 fishes with a daily dose of 0.16 g/kg for 15 days. The challenge tests by V. anguillarum were carried out 30, 60 and 90 days after the vaccination. In the vaccinated groups, the survival rates after the challenge were 98, 86 and 78%, respectively; and in the control group, were 86, 52 and 50%, respectively.
2) Three hundreds and fifty fishes were dipped in 7% NaCl solution for 2 minutes, and then in vaccine solution for 3 minutes. In the vaccinated groups, the survival rates after the challenges that were started 30, 60 and 90 days after the vaccination were 100, 94 and 100%, respectively; and, in the control group, were 86, 52 and 50%, respectively.
3) From the experimental results on the consecutive usega of the vaccine solution, it may be concluded that the vaccine solution can be used for at least 3 times. These results showed us that the hyperosmotic vaccination makes it possible to treat over 3 times as much of ayu as oral one.
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