Immersion vaccination with a biomimetic mucoadhesive nanovaccine has been shown to induce a strong mucosal immune response against columnaris disease, a serious bacterial disease in farmed red tilapia caused by Flavobacterium columnare. However, the induction of a systemic immune response by the vaccine is yet to be investigated. Here, we examine if a specific humoral immune response is stimulated in tilapia by a biomimetic-mucoadhesive nanovaccine against Flavobacterium columnare using an indirect-enzyme-linked immunosorbent assay (ELISA), serum bactericidal activity (SBA) and the expression of immune-related genes within the head-kidney and spleen, together with assessing the relative percent survival of vaccinated fish after experimentally infecting them with F. columnare. The anti-IgM antibody titer of fish at 14 and 21 days post-vaccination was significantly higher in chitosan complex nanoemulsion (CS-NE) vaccinated fish compared to fish vaccinated with the formalin-killed vaccine or control fish, supporting the serum bactericidal activity results at these time points. The cumulative mortality of the unvaccinated control fish was 87% after challenging fish with the pathogen, while the cumulative mortality of the CS-NE vaccinated group was 24%, which was significantly lower than the formalin-killed vaccinated and control fish. There was a significant upregulation of IgM, IgT, TNF α, and IL1-β genes in the spleen and kidney of vaccinated fish. Significant upregulation of IgM and IgT genes was observed in the spleen of CS-NE vaccinated fish. The study confirmed the charged-chitosan-based mucoadhesive nanovaccine to be an effective platform for immersion vaccination of tilapia, with fish generating a humoral systemic immune response against columnaris disease in vaccinated fish.

Tilapia is the world’s most extensively farmed species after carp. It is an attractive species for aquaculture as it grows quickly, reaching harvest size within six to seven months of production, and provides an important source of food and revenue for many low-income families, especially in low- to middle-income countries. The expansion of tilapia aquaculture has resulted in an intensification of farming systems, and this has been associated with increased disease outbreaks caused by various pathogens, mostly bacterial and viral agents. Vaccination is routinely used to control disease in higher-value finfish species, such as Atlantic salmon. At the same time, many tilapia farmers are often unwilling to vaccinate their fish by injection once the fish have been moved to their grow-out site. Alternative vaccination strategies are needed to help tilapia farmers accept and use vaccines. There is increasing interest in nanoparticle-based vaccines as alternative methods for delivering vaccines to fish, especially for oral and immersion administration. They can potentially improve vaccine efficacy through the controlled release of antigens, protecting antigens from premature proteolytic degradation in the gastric tract, and facilitating antigen uptake and processing by antigen-presenting cells. They can also allow targeted delivery of the vaccine at mucosal sites. This review provides a brief overview of the bacterial and viral diseases affecting tilapia aquaculture and vaccine strategies for farmed tilapia. It focuses on the use of nanovaccines to improve the acceptance and uptake of vaccines by tilapia farmers.

The aim of the present study was to optimize a masculinization platform for the production of all-male red tilapia fry by oral administration of 30 and 60 ppm of MT and alkyl polyglucoside nanostructured lipid carriers (APG-NLC) loaded with MT, respectively, for 14 and 21 days. The characterization, encapsulation efficiency and release kinetics of MT in lipid-based nanoparticles were assessed in vitro. The results showed that the MT-loaded nanoparticles were spherical, ranging from 80 to 125 nm in size, and had a negative charge with a narrow particle distribution. The APG-NLC loaded with MT provided higher physical stability and encapsulation efficacy than the NLC. The release rate constants of MT from MT-NLC and MT-APG-NLC were higher than those of free MT, which is insoluble in aqueous media. There was no significant difference in survival between the fish administered MT or the those fed orally with MT-APG-NLC fish. According to the logistic regression analysis, the sex reversal efficacy of MT-APG-NLC (30 ppm) and MT (60 ppm), resulted in significantly higher numbers of males after 21 days of treatment compared with the controls. The production cost of MT-APG-NLC (30 ppm) after 21 days of treatment was reduced by 32.9% compared with the conventional MT treatment group (60 ppm). In all the treatments, the length–weight relationship (LWR) showed negatively allomeric growth behavior (b < 3), with a relative condition factor (K_n) of more than 1. Therefore, MT-APG-NLC (30 ppm) would seem to be a promising, cost-effective way to reduce the dose of MT used for the masculinization of farmed red tilapia.

Whiteleg shrimp (Penaeus vannamei) have been vulnerable to the stress induced by different aquaculture operations such as capture, handling, and transportation. In this study, we developed a novel clove oil-nanostructured lipid carrier (CO-NLC) to enhance the water-soluble capability and improve its anesthetic potential in whiteleg shrimp. The physicochemical characteristics, stability, and drug release capacity were assessed in vitro. The anesthetic effect and biodistribution were fully investigated in the shrimp body as well as the acute multiple-dose toxicity study. The average particle size, polydispersity index, and zeta potential value of the CO-NLCs were 175 nm, 0.12, and −48.37 mV, respectively, with a spherical shape that was stable for up to 3 months of storage. The average encapsulation efficiency of the CO-NLCs was 88.55%. In addition, the CO-NLCs were able to release 20% of eugenol after 2 h, which was lower than the standard (STD)-CO. The CO-NLC at 50 ppm observed the lowest anesthesia (2.2 min), the fastest recovery time (3.3 min), and the most rapid clearance (30 min) in shrimp body biodistribution. The results suggest that the CO-NLC could be a potent alternative nanodelivery platform for increasing the anesthetic activity of clove oil in whiteleg shrimp (P. vannamei).