Efikasi Vaksinasi Booster Oral Streptococcus agalactiae terhadap Kelangsungan Hidup dan Respons Imun Ikan Nila (Oreochromis niloticus)

Abstract

Streptokokosis akibat Streptococcus agalactiae merupakan kendala utama budidaya ikan nila yang menimbulkan mortalitas tinggi. Vaksinasi oral dinilai efisien untuk stadia benih, namun degradasi antigen di saluran pencernaan menyebabkan durasi proteksi singkat, sehingga diperlukan strategi booster. Penelitian ini bertujuan menganalisis efikasi vaksinasi booster oral S. agalactiae terhadap tingkat proteksi benih ikan nila. Penelitian menggunakan rancangan acak lengkap dengan lima perlakuan, yaitu kontrol negatif, kontrol positif, vaksin primer, booster tunggal, dan booster ganda, dengan dosis 107 CFU/g pakan. Uji tantang dilakukan pada hari ke-14, ke-28, dan ke-42. Parameter yang diukur meliputi mortalitas, kelangsungan hidup relatif, titer antibodi, gambaran darah, aktivitas fagositik, serta laju pertumbuhan spesifik. Hasil menunjukkan perlakuan booster ganda memberikan proteksi terbaik dengan kelangsungan hidup relatif 68,75%, titer antibodi 6,00 log2, dan laju pertumbuhan spesifik 3,84%/hari, disertai gambaran darah dan aktivitas fagositik tertinggi secara konsisten. Vaksinasi booster oral ganda S. agalactiae terbukti efektif meningkatkan respons imun dan tingkat proteksi benih ikan nila terhadap infeksi S. agalactiae, sehingga berpotensi diaplikasikan dalam praktik budidaya untuk menekan mortalitas akibat streptokokosis.

Streptococcosis caused by Streptococcus agalactiae is a major constraint in Nile tilapia aquaculture, leading to high mortality. Oral vaccination is considered efficient for the fingerling stage; however, antigen degradation in the digestive tract results in a short duration of protection, necessitating a booster strategy. This study aimed to analyze the efficacy of oral booster vaccination with S. agalactiae on the protection level of Nile tilapia fingerlings. A completely randomized design was applied with five treatments: negative control, positive control, primary vaccine, single booster, and double booster, at a dose of 107 CFU/g feed. Challenge tests were conducted on days 14, 28, and 42. The measured parameters included mortality, relative percent survival, antibody titer, blood profile, phagocytic activity, and specific growth rate. The results showed that the double booster treatment provided the best protection, with a relative percent survival of 68.75%, antibody titer of 6.00 log2, and specific growth rate of 3.84%/day, accompanied by consistently the highest blood profile and phagocytic activity. Oral double booster vaccination with S. agalactiae effectively enhanced the immune response and protection level of Nile tilapia fingerlings against S. agalactiae infection, making it a promising strategy for application in aquaculture practice to reduce streptococcosis-related mortality.