Comparative Efficacy and Immunologicity of Oral and Injectable DNA Vaccination Against Streptococcus agalactiae in Nile Tilapia (Oreochromis niloticus)

Moftakhar, Parisaa; Alishahi, Mojtaba; Tabandeh, Mohammad Reza; Khosravi, Mohammad; Gharbavi, Mahmoud

Volume 17, Issue 4 (Winter 2026) 3 2026, 17(4): 18-37 | Back to browse issues page

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Moftakhar P, Alishahi M, Tabandeh M R, Khosravi M, Gharbavi M. Comparative Efficacy and Immunologicity of Oral and Injectable DNA Vaccination Against Streptococcus agalactiae in Nile Tilapia (Oreochromis niloticus). 3 2026; 17 (4) :18-37
URL: http://jmb.ahvaz.iau.ir/article-1-1102-en.html

Comparative Efficacy and Immunologicity of Oral and Injectable DNA Vaccination Against Streptococcus agalactiae in Nile Tilapia (Oreochromis niloticus)

Parisaa Moftakhar

, Mojtaba Alishahi

, Mohammad Reza Tabandeh

, Mohammad Khosravi

, Mahmoud Gharbavi

Department of Livestock, Poultry and Aquatic Animals Health, Faculty of Veterinary Medicine, Shahid Chamran University of Ahvaz, Ahvaz, Iran.

Abstract: (302 Views)

Vaccination remains the most effective strategy for mitigating streptococcosis in tilapia culture. The inherent advantages of third-generation vaccines have increasingly shifted the focus of aquatic health management toward DNA-based platforms. This study aimed to evaluate the immunogenicity, efficacy, and growth-promoting potential of a novel DNA vaccine based on the BibA gene of Streptococcus agalactiae, comparing oral and injectable delivery routes with a traditional traditional formalin-killed Cells (FKC). A total of 225 Nile tilapia (Oreochromis niloticus; 19.4 ± 3.25 g) were randomly assigned to five experimental groups in triplicate. Groups 1 and 2 received the BibA-DNA vaccine via oral and injectable routes, respectively, while Groups 3 and 4 were immunized with the FKC through the same administration routes. A fifth group served as the control. Fish were maintained under standardized conditions for 75 days, with biometric assessments and blood sampling conducted on days 30, 60, and 75. Growth indices, specific antibody titers, and non-specific immune parameters were analyzed. Subsequently, all groups were challenged with virulent S. agalactiae, and cumulative mortality was monitored for 14 days. Results showed that both injectable vaccines (DNA and FKC) exhibited significantly higher non-specific immune responses and specific antibody titers compared to the control and oral groups (P < 0.05). In contrast, oral administration did not significantly modulate most immunological parameters (P > 0.05). Post-challenge results revealed relative percent survival (RPS) values of 70% and 75% for the injectable DNA and FKC groups, respectively. For oral delivery, the DNA vaccine outperformed the FKC, yielding an RPS of 40% compared to 35% in the killed vaccine group. Notably, injectable treatments showed a significant improvement in growth performance (P < 0.05). Hematological profiles remained unaffected by vaccine type or delivery route (P > 0.05). Our findings demonstrate that the injectable BibA -DNA vaccine offers protective efficacy comparable to the traditional killed vaccine while providing superior growth performance. Furthermore, the DNA-based platform exhibited higher potential for oral immunization compared to the inactivated vaccine, suggesting it is a promising candidate for the sustainable management of streptococcosis in tilapia aquaculture.

Keywords: Streptococcus agalactiae, DNA vaccine, Nile tilapia, immunogenicity, BibA gene.e.

Full-Text [PDF 1234 kb] (105 Downloads)

Type of Study: Research | Subject: Special
Received: 2026/02/16 | Accepted: 2026/05/2 | Published: 2026/05/2