The impact of several hydraulic fracking chemicals on Nile tilapia and evaluation of the protective effects of Spirulina platensis

Isolation, in vitro, and in vivo pathogenicity test of Tilapia lake virus (TiLV) and development of a prognostic semi-quantitative lesion scoring system for differentiating clinical/subclinical infection in farmed tilapia (Oreochromis niloticus L.)

Tilapia lake virus ('TiLV-MH-2022') was recently recovered from the naturally infected farmed tilapia. Reverse transcription-polymerase chain reaction (RT-PCR) using segment 1 specific primers, followed by Sanger sequencing, confirmed the infection. The pairwise sequence homology of segment 1 showed its close relationship with the previous isolates. The virus was successfully detected from the mucus, which emphasised the possibility of non-invasive screening of tilapia on a large scale. The virus inoculum prepared from the infected tissues was tested for in vivo and in vitro pathogenicity. Around 100-140 nm-sized electron-dense virus particles were observed in the infected OnlL cells. Based on the onset of symptoms and lesions, all RT-PCR-positive fish were categorised into two groups, 'clinical' and 'subclinical'. A lesion-scoring technique was developed for assessing the pathogenicity of the virus isolate. The external and internal gross lesions and histopathological alterations in the critical organs of the fish, such as the brain, kidney, gills, and liver, were assessed on a scale of 0 (no gross lesion) to 5 (most severe lesions). Overall lesion score was significantly high in the clinical and subclinical groups for gross and histopathology, respectively. This study is the first such attempt to standardise a semi-quantitative lesion scoring technique for TiLV infection, which establishes a clinical relevance and prognostic ability to distinguish between the apparent and inapparent infection.

Moringa oleifera Leaf Powder Dietary Inclusion Differentially Modulates the Antioxidant, Inflammatory, and Histopathological Responses of Normal and Aeromonas hydrophila-Infected Mono-Sex Nile Tilapia (Oreochromis niloticus)

This study aimed to detect the impact of Moringa oleifera leaf powder dietary inclusion on the antioxidant and innate immune responses of mono-sex Nile tilapia fingerlings. A total of 180 fingerlings were allocated in a random method into three groups with triplicate each. One group (1^st group) received the control diet (basal diet (BD) free of moringa) and the other groups (2^nd and 3^rd) fed BD containing M. oleifera leaf powder at 5 and 10% of the diet, respectively. After 6 weeks of feeding, fish were randomly redistributed into four replicates and rested for 24 h. Then, each fish in the first two replicates was injected with 0.2 mL of PBS, while the others were injected with 0.2 mL of A. hydrophila suspension (1.8 × 10⁶ CFU/mL). Healthy fish fed on M. oleifera leaf powder showed enhanced immune response manifested by significant increases in phagocytic and lysozyme activities with a marked H/L ratio (P < 0.05). In addition, significant alterations of the lymphocytic and heterophilic population in circulation with increasing infiltration in tissue such as the spleen were noticed. Also, M. oleifera significantly upregulated the antioxidants, CAT and GPx, proinflammatory cytokines, IL1-β, IL-8, and IFN-γ relative mRNA levels. On the other hand, following A. hydrophila challenging conditions, M. oleifera caused downregulations of IL1-β, IL-8, and IFN-γ transcription levels, and also lowered the CAT and GPx mRNA levels. In addition, a marked reduction of leukocytic infiltration plus a significant improvement of the degenerative changes in intestinal architecture has occurred. So, M. oleifera leaf powder can be included in the fish diet to enhance immune response under normal health conditions and lower the infection-associated inflammatory response.