Abstract
In this study, the possibility of using passive immunization with rabbit immunoglobulin (RIg) as a preventive measure and a medical treatment for pseudotuberculosis in cultured yellowtail, Seriola quinqueradiata, was investigated.
Yellowtail were passively immunized with RIg prepared from anti-Pasteurella piscicida rabbit serum by intraperitoneal injection. The absorption of RIg into serum and skin mucus after immunization were examined. The artificial challenges with virulent P. piscicida were carried out 6, 12, 24 hours before and 1, 12, 24 hours after immunization. The efficacy of passive immunization from the results was studied.
In immunized fish, agglutinating antibody titers in sera increased rapidly and the highest mean titer of 1: 42 was obtained 3 hours after immunization. Maximum concentration of RIg in serum was detected 12 hours after immunization. However, no RIg was detected in serum after 24 hours post-immunization, and neither in all of skin mucus samples. Survival ratios for 8 days after challenge of fish immunized passively were not less than 70% in comparison with 0% survival in the control. On the contrary, survival ratios for 8 days after passive immunization of challenged fish were not more than 30%. It is concluded that passive immunization of yellowtail against pseudotuberculosis with RIg is highly effective for at least 24 hours after immunization.
