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¹ National Fish Health Research Centre (NaFisH), Fisheries Research Institute (FRI) Batu Maung, Department of Fisheries Malaysia, 11960 Batu Maung, Penang, Malaysia
² Department of Marine Science, Kulliyyah of Science, International Islamic University Malaysia, Bandar Indera Mahkota, 25200 Kuantan, Pahang, Malaysia
³ Kulliyyah of Allied Health Science, International Islamic University Malaysia, Bandar Indera Mahkota, 25200 Kuantan, Pahang, Malaysia
⁴ Faculty of Veterinary Medicine, Universitas Airlangga, Jl. Mulyorejo, Kec. Mulyorejo, 60115 East Java, Surabaya, Indonesia DOI : 10.4194/AQUAST2188 Viewed : 143 - Downloaded : 105 Streptococcosis poses a considerable threat to tilapia farming, necessitating the urgent development of an effective vaccine. Previous laboratory trials indicated the potential of palm oil as a vaccine adjuvant in a feed-based formulation. The present study further investigated the vaccine`s efficacy using a similar formulation under field conditions. A total of 6.000 healthy juvenile red hybrid tilapias were divided into three groups: an unvaccinated control, a single booster group (vaccinated twice), and a double booster group (vaccinated thrice). The vaccine was administered orally at 5% of body weight. Organ samples and blood serum were collected biweekly over 16 weeks for bacterial isolation and immune response analysis, including immunoglobulin M (IgM), lysozyme, and complement C3 quantification. Serum IgM levels significantly increased (P<0.05) in all vaccinated groups, peaking at week 4. An additional booster given at week 6 in the double booster group resulted in sustained high IgM levels throughout the study. The isolation rates of S. agalactiae were lower in vaccinated groups, with mortality rates decreasing from 23.6% (unvaccinated) to 6.4% (double booster). These results indicate that oral administration of palm oil adjuvanted vaccine stimulates serum antibody (IgM), lysozyme, and complement C3 responses, reduces the incidence of streptococcosis, and improves the survival rate to 93.6%. Keywords : Streptococcus agalactiae Streptococcosis Tilapia Vaccine Oral vaccine