Pre-treatment of Nile tilapia (Oreochromis niloticus) with ozone nanobubbles improve efficacy of heat-killed Streptococcus agalactiae immersion vaccine.

Nanobubble technology has shown appealing technical benefits and potential applications in aquaculture. We recently found that treatment with ozone nanobubbles (NB-O3) activated expression of several immune-related genes leading to effective response to subsequent exposure to fish pathogens. In this study, we investigated whether pre-treatment of Nile tilapia (Oreochromis niloticus) with NB-O3 can enhance specific immune responses and improve efficacy of immersion vaccination against Streptococcus agalactiae. Spleen and head kidney of fish in the vaccinated groups showed a substantial upregulation in expression levels of pro-inflammatory cytokine genes (IL-1ß, TNF-α, IL-6) and immunoglobulin classes (IgM, IgD, IgT) compared with the unvaccinated control groups. The mRNA transcript of pro-inflammatory cytokine genes was greatest (approx. 2.8-3.3 folds) on day 7 post-vaccination, whereas the relative expression of immunoglobulin genes was greatest (approx. 3.2-4.1 folds) on day 21 post-immunization. Both systemic and mucosal IgM antibodies were elicited in vaccinated groups. As the result, the cumulative survival rate of the vaccinated groups was found to be higher than that of the unvaccinated groups, with a relative percent survival (RPS) ranging from 52.9 to 70.5%. However, fish in the vaccinated groups that received pre-treatment with NB-O3, bacterial antigen uptakes, expression levels of IL-1ß, TNF-α, IL-6,IgM, IgD, and IgT, as well as the specific-IgM antibody levels and percent survival, were all slightly or significantly higher than that of the vaccinated group without pre-treatment with NB-O3. Taken together, our findings suggest that utilizing pre-treatment with NB-O3 may improve the immune response and efficacy of immersion vaccination in Nile tilapia.

Ozone nanobubble modulates the innate defense system of Nile tilapia (Oreochromis niloticus) against Streptococcus agalactiae.

Ozone nanobubble (NB-O3) is a promising technology for improving dissolved oxygen and reducing bacterial concentration in aquaculture systems. Here, we investigated the effects of NB-O3 on the innate immunity of fish by monitoring the expression levels of nonspecific immune-related genes (IL-1ß, IL-2ß, TNF-α), heat-shock protein genes (HSP70, HSP90-α), and a bacteriolytic enzyme, C-type lysozyme, gene (LYZ) post-treatment with this technology. Following exposure to NB-O3, the different tissues of Nile tilapia (Oreochromis niloticus) were collected over time for quantitative real-time PCR (qPCR) analysis. The expression of all the genes evaluated in the gills, the head kidney, and the spleen of the NB-O3 treated group was significantly up-regulated compared to that in the untreated control group. The expression levels were the highest (approx. 2 to 4-fold) at 15 min and 3 h post-exposure and then decreased from 6 to 24 h. These findings suggested that NB-O3 could switch on the innate immunity genes of Nile tilapia. Thus, we hypothesized that the NB-O3-immune-activated fish would respond more effectively to subsequent bacterial infections, thereby improving survivability compared to that of untreated fish. To test this hypothesis, 3 h post NB-O3 exposed fish and unexposed fish were challenged with a lethal dose of Streptococcus agalactiae. Interestingly, the survival rate of the NB-O3 group was significantly higher than that of the non-treated controls, with a relative percent survival (RPS) of 60-70%. Together, these findings indicate, for the first time, that NB-O3 may trigger the nonspecific defense system of the fish, thereby improving fish survivability during subsequent bacterial infections. This research identified another potential benefit of NB-O3 in aquaculture for preventing infectious bacterial diseases.

Use of geographic information systems for assessing groundwater pollution potential by pesticides in Central Thailand.

This study employed geographic information systems (GIS) technology to evaluate the vulnerability of groundwater to pesticide pollution in Thailand. The study area included three provinces, Kanchana Buri, Ratcha Buri, and Suphan Buri, located in west-central Thailand. Factors used for the vulnerability assessment included soil texture, slope, land use, well depth, and rainfall. These vulnerability factors were reclassified to a common scale, and a weighted average was computed to yield a vulnerability score. Vulnerability factors and weights were assigned considering pesticide concentrations in 90 wells throughout the study area. Well depth was the most significant vulnerability factor. Groundwater vulnerability maps were generated for several pesticides. The eastern, agricultural part of the study area has relatively deep wells and fine soils. Shallow wells are present in the mountainous west; however, fewer pesticides are applied in that region. Consequently, much of the study area had a medium groundwater vulnerability rating, although there were pockets of high vulnerability, for example, in agricultural areas with shallow wells. The groundwater vulnerability maps are effective for identifying locations warranting more detailed groundwater pollution and vulnerability investigations.