Immunization of Basa fish (Pangasius bocourti) against Ichthyophthirius multifiliis with live and sonicated trophonts

The high density of Basa fish (Pangasius bocourti) culture leads to outbreaks of Ichthyophthirius multifiliis (Ich), also knows as white spot disease. In this research, immunization of Basa fish against Ich with live and sonicated trophonts by intraperitoneal (IP) injection was investigated. Anti‑Ich antibody titer was determined using ELISA and Western immunoblotting 21 days post immunization. The results revealed that preimmunized fish, non‑immunized fish and fish immunized with bovine serum albumin (BSA) at a concentration 65 µg g^-1 fish did not show specific antibody against Ich. 21 days post immunization, fish immunized with live trophonts exhibited higher anti‑Ich antibody titer than fish immunized with sonicated trophonts at the same antigen concentration. Fish immunized with 65 µg trophonts protein/g fish live trophonts showed the highest titer 1:1,000 (p 0.05). The results from Western immunoblotting showed two parasite protein bands of 66 kDa and 14 kDa, which reacted with antibodies from serum of immune fish. No fish in the nonimmunized group survived. At the same concentration of antigen (65 µg g^-1), fish immunized with live trophonts exhibited the highest survival rate, 63.33 ±5.77% (p 0.05). Therefore, these results are the Basa fish immunizing procedure will be the way to conduct immunization against Ich to prevent disease outbreaks in aquaculture.