抄録
Efficacy of various direct immersion methods was investigated for the development of a practical vaccine against pseudotuberculosis in cultured yellowtail. Formalin-killed Pasteurella piscicida was used to immunize fish, one, two, three times by immersion and a combination of single immersion and oral vaccination methods. An artificial infection at three doses of P. piscicida to determine efficacy of various administered methods was carried out three weeks after the first vaccination. The relative percent survival at ten days after artificial infectionwere:a) 8.0×104 cfu/ml:0% in one immersion, 7% in two immersion, 13% in three immersions 17% in immersion+oral methods; b) 8.0×103 cfu/ml: 22% in one immersion, 39% in two im-mersions, 51% in three immersions and 65% in immersion+oral methods and c) 8.0×102 cfu/mt: 30% in immersion+oral methods. Agglutination titers against P. piscicida in the serum and skin mucus were determined in vaccinated fish prior to artificial infection and were observed to be enhanced with increasing frequency of immersion. In addition, agglutination titers against P. piscicida were observed in the intestinal mucus of fish vaccinated by three times immersion and a combination of immsersion and oral methods. Efficacy of direct immsersion methods increased with increasing administration times and combined with oral vaccination methods.
