Department of Aquaculture, Faculty of Agriculture, Universiti Putra Malaysia (UPM), 43400, Serdang, Selangor, Malaysia.
Department of Veterinary Pathology and Microbiology, Faculty of Veterinary Medicine, Universiti Putra Malaysia (UPM), 43400, Serdang, Selangor, Malaysia.
BMC Vet Res. 2020 Jul 2;16(1):226. doi: 10.1186/s12917-020-02443-y.
Streptococcosis and Motile Aeromonad Septicemia (MAS) are important diseases of tilapia, Oreochromis spp. and causes huge economic losses in aquaculture globally. The feed-based vaccination may be an alternative to minimize major infectious diseases in tilapia. Thus, this study aims to evaluate the haemato-immunological responses and effectiveness of a newly developed feed-based killed bivalent vaccine against Streptococcus iniae and Aeromonas hydrophila in hybrid red tilapia. A total of 495 hybrid red tilapia of 61.23 ± 4.95 g were distributed into 5 groups (each with triplicate). The fish were immunized orally through bivalent (combined S. iniae and A. hydrophila) spray vaccine (BS group), bivalent formulate vaccine (BF group), monovalent S. iniae vaccine (MS group), monovalent A. hydrophila vaccine (MA group) and unvaccinated as a control group. The vaccine was orally administered on days 0, 14 and 42 applied feed-based bacterin at 5% body weight. The blood and spleen samples were collected from all groups on 7, 21 and 49 days post-vaccination, and also 96 h post-infection to assess their haemato-immune responses.
Compared with the unvaccinated group, leukocyte, lymphocytes, monocytes, granulocytes counts in vaccinated groups were significantly (P < 0.05) increased on 21, 49 days post-vaccination and also 96 h post-infection, while erythrocytes, haemoglobin and haematocrit in vaccinated groups were significantly (P < 0.05) enhanced only 96 h post-infection. Additionally, the lysozyme and phagocytic activity and, serum antibody (IgM) were significantly higher (P < 0.05) against S. iniae and A. hydrophila in vaccinated groups compared to the unvaccinated group in the pre- and post-infection. Results from the challenge through co-infection with S. iniae and A. hydrophila showed the relative percent survival (RPS) in BF group was 76.67 ± 4.71%, which had the capacity to induce significant protection (P < 0.05) compared to others groups.
This study demonstrates the bivalent formulate (BF) group could elicit significant non-specific and specific immunological responses with higher protection in hybrid red tilapia. In addition, this newly developed feed-based bivalent vaccination can be a promising technique for effective and large scale fish immunization in the aquaculture industry.
链球菌病和运动性气单胞菌败血症（MAS）是罗非鱼 Oreochromis spp. 的重要疾病，在全球水产养殖中造成了巨大的经济损失。基于饲料的疫苗接种可能是减少罗非鱼主要传染病的一种替代方法。因此，本研究旨在评估一种新开发的针对无乳链球菌和嗜水气单胞菌的双价口服灭活疫苗对杂交红罗非鱼的血液免疫反应和效果。将 495 条体重为 61.23±4.95g 的杂交红罗非鱼分为 5 组（每组 3 个重复）。通过双价（组合无乳链球菌和嗜水气单胞菌）喷雾疫苗（BS 组）、双价配方疫苗（BF 组）、单价无乳链球菌疫苗（MS 组）、单价嗜水气单胞菌疫苗（MA 组）和未接种疫苗的对照组（NC 组）对鱼进行口服免疫。在第 0、14 和 42 天，按 5%体重投喂饲料基菌苗。在免疫后第 7、21 和 49 天以及感染后 96 小时从所有组收集血液和脾脏样本，以评估其血液免疫反应。
与未接种疫苗的对照组相比，接种疫苗组的白细胞、淋巴细胞、单核细胞和嗜中性粒细胞计数在免疫后第 21、49 天和感染后 96 小时显著增加（P<0.05），而接种疫苗组的红细胞、血红蛋白和血细胞比容仅在感染后 96 小时显著增加（P<0.05）。此外，与未接种疫苗的对照组相比，接种疫苗组的溶菌酶和吞噬活性以及血清抗体（IgM）对无乳链球菌和嗜水气单胞菌的反应均显著升高（P<0.05）。在感染前和感染后，通过混合感染无乳链球菌和嗜水气单胞菌进行的攻毒试验显示，BF 组的相对存活率（RPS）为 76.67±4.71%，具有显著的保护能力（P<0.05），与其他组相比。
本研究表明，双价配方（BF）组可在杂交红罗非鱼中引起显著的非特异性和特异性免疫反应，并提供更高的保护。此外，这种新开发的基于饲料的双价疫苗接种可能是水产养殖中有效和大规模鱼类免疫的一种有前途的技术。
