The effect of mistletoe, Viscum album coloratum, extract on innate immune response of Nile tilapia (Oreochromis niloticus)

Effects of dietary walnut (Juglans regia) leaves extract on immunity, gene expression responses, and disease resistance in Oreochromis niloticus

The dietary effects of walnut leaf extract (WLE) on the growth, immunity, and resistance of Oreochromis niloticus to bacterial infection have been investigated. Five diets were prepared with various WLE doses of 0, 250, 500, 750, and 1000 mg/kg, termed as Con (control), WLE250, WLE500, WLE750, and WLE1000, respectively. Fish (11.67 ± 0.21 g) were fed these diets for 60 days and then challenged with Plesiomonas shigelloides. Before the challenge, it was observed that dietary WLE did not significantly affect the growth, blood proteins (globulin, albumin, and total protein), and liver function enzymes (ALT and AST) activities. The WLE250 group significantly increased serum SOD and CAT activities more than other groups. The serum immunological indices (lysozyme and myeloperoxidase activities) and hematological parameters (phagocytic activity %, phagocytic index, respiratory burst activity, and potential activity) were significantly increased in the WLE groups compared with the Con group. The expression of IgM heavy chain, IL-1β, and IL-8 genes were significantly upregulated in all WLE-supplemented groups in comparison with the Con group. The fish survival rates (SR; %) post challenge in the Con, WLE250, WLE500, WLE750 and WLE1000 groups were 40.0%, 49.3%, 86.7%, 73.3%, and 70.7%, respectively. The Kaplan-Meier survivorship curves illustrated that the highest SR% was found in the WLE500 group (86.7%) amongst the other groups. Accordingly, we can suggest that feeding O. niloticus with a diet supplied with WLE at a dose rate of 500 mg/kg over 60 days could enrich haemato-immune responses and increase the fish survival against the challenge with P. shigelloides. These results recommend using WLE as a herbal dietary supplement to substitute antibiotic use in aquafeed.

A review on pathogenicity of Aeromonas hydrophila and their mitigation through medicinal herbs in aquaculture

Aeromonas hydrophila is a freshwater, facultatively anaerobic, chemo-organoheterotrophic bacterium that distressed fishes with gastroenteritis, septicemia and causes a disease known as Motile Aeromonas Septicemia (MAS), which affects the aquatic environment. Haemolysin, aerolysin, cytosine, gelatinase, enterotoxin and antimicrobial peptides have been identified as virulence factors in A. hydrophila. Medicinal herbs/plants and their uses are the instant, easily available, cost-effective, efficient and eco-friendly approach for socio-economic, sustainable development of modern aquaculture practice. Phytotherapy either through a dip or by incorporation into the diets is an alternative approach to synthetic pharmaceuticals to diminish the pathogenicity of aquatic environmental pathogens. Due to the presence of remarkable phytoconstituents like flavonoids, alkaloids, pigments, terpenoids, steroids and essential oils, the medicinal plant exhibits anti-microbial, appetite-stimulating, anti-stress, growth-promoting and immunostimulatory activities. Aqua-industry preferred phytotherapy-based techniques/compounds to develop resistance against a variety of aquatic pathogens in culturable fishes because they are inexpensive and environment-friendly. As a result, this review elaborates on the diverse applications of phytotherapy as a promising tool for disease management in aquaculture and a major step toward organic aquaculture.

Pyrogallol downregulates the expression of virulence-associated proteins in Acinetobacter baumannii and showing anti-infection activity by improving non-specific immune response in zebrafish model

Acinetobacter baumannii, a virulent uropathogen with widespread antibiotic resistance, has arisen as a critical scientific challenge, necessitating the development of innovative therapeutic agents. This is the first study reveal the proteomic changes in A. baumannii upon pyrogallol treatment for understanding the mechanisms using nano-LC-MS/MS-based quantitative proteomics and qPCR analysis. The obtained results found that pyrogallol treatment dramatically downregulated the expression level of several key proteins such as GroEL, DnaK, ClpB, SodB, KatE, Bap, CsuA/B, PgaA, PgaC, BfmR, OmpA, and SecA in A. baumannii, which are involved in chaperone-mediated oxidative stress responses, antioxidant defence system, biofilm formation, virulence enzyme production, bacterial adhesion, capsule formation, and antibiotic resistance. Accordingly, the pyrogallol dramatically enhanced the lifespan of A. baumannii-infected zebrafish by inhibiting bacterial colonization, demonstrating the anti-infective potential of pyrogallol against A. baumannii. Further, the histopathological results also demonstrated the disease protection efficacy of pyrogallol against the pathognomonic sign of A. baumannii infection. In addition, the pyrogallol treatment effectively improved the immune parameters such as serum myeloperoxidase activity, leukocyte respiratory burst activity, and serum lysozyme activity in zebrafish against A. baumannii infection. Based on the results, the present study strongly proposes pyrogallol as a promising therapeutic agent for treating A. baumannii infection.

Role of phytobiotics in relieving the impacts of Aeromonas hydrophila infection on aquatic animals: A mini-review

Aeromonas hydrophila is a ubiquitous bacterium with various hosts that causes mass mortality in farm-raised fish species and significant economic losses. The current antibiotic treatment is ineffective in controlling this bacterium infection in aquaculture species. Therefore, an evaluation of potential phytobiotics is needed to find an alternative antimicrobial agent to reduce the over-reliance on antibiotics in aquaculture and safeguard public and environmental health. Furthermore, the rise in antibiotic resistance cases among pathogenic bacteria indicates an urgent need for new fish and shellfish health management solutions. In this context, phytobiotics applications in aquaculture can be defined as any medicinal plant-based antimicrobial agent used in fish and shellfish health management. This review will focus on the impacts of Motile Aeromonas Septicemia (MAS) due to A. hydrophila in aquaculture, the potential of phytobiotics in enhancing the tolerance of aquaculture species against MAS and the combination of phytobiotics with other antimicrobial and therapeutic agents against MAS.

Advances in the complement system of a teleost fish, Oreochromisniloticus

As the earliest known vertebrate possessing a complete immune system, teleost fish played an important role in the evolution of this system. The complement system is an ancient defense mechanism present in invertebrates and vertebrates. In teleost fish the complement system is formed by more than 35 circulating proteins, or found at the cell surface. This system is activated by three pathways: alternative, classical and lectin, generating functions such as the opsonization, lysis and modulation of the innate and adaptive immune responses. The complement system is an important immunological indicator that can be used to study and monitor the effects of environmental, nutritional, and infectious processes. The Nile tilapia (Oreochromis niloticus) is a teleost fish of great economic interest due to its characteristics of easy cultivation, high growth rates, and tolerance to adverse environmental conditions. In addition, Nile tilapia is an excellent model for ecotoxicological studies, however, there are very few studies reporting the performance of the complement system in this species after exposure to environmental pollutants. The aim of this review is to gather recent studies with to address the molecular and functional characterizations of the complement system in Nile tilapia and provide new insights about this defense mechanism. Looking to the future, we believe that the complement system analysis in Tilapia can be used as a biomarker of water quality and the general health status of fish.

Alterations of haemato-biochemical parameters pre and post-challenge with Aeromonas hydrophila and survival of Oreochromis mossambicus fed Moringa oleifera-based diets

This study investigated the extent of changes in haemato-biochemical and immunological parameters of O. mossambicus fed with M. oleifera-based diets pre and post-challenge with different concentrations of A. hydrophila. Moringa oleifera powdered leaves were added to five experimental diets at 0%, 3%, 6%, 9% and 12%, designated D1, D2, D3, D4 and D5, respectively. Each diet was randomly fed to triplicate groups of 45 fish (33.46 ± 1.57 g) for 45 days. There were no significant differences (P > 0.05) in WG, FCR and SGR between treatments. There was an increase in WBC, RBC, HGB and HCT with increasing M. oleifera levels. No significant changes (P > 0.05) were observed in AST, ALT, ALP and LDH levels between treatments. After 45 days, fish from each treatment were injected with varying concentrations (0, 1 × 10⁶ cfu, 1.5 × 10⁶ cfu, 3 × 10⁶ cfu and 4 × 10⁶ cfu ml^-1) of Aeromonas hydrophila. There was a significant decline in RBC, HGB and HCT of fish in the D1-D3 compared to the D4 and D5 groups. There was an increase in AST, ALT, ALP and LDH in the D1-D3 groups while no significant changes (P > 0.05) were observed in the D4 and D5 groups between bacterial concentrations. Survival rate was lower in the D1-D3 compared to the D4 and D5 groups, indicating that immunity was enhanced in fish fed with the highest M. oleifera inclusion levels. NBT and lysozyme activities were also lower in the D1-D3 groups compared to the D4 and D5 groups. The enhancement of immunity is attributed to the presence of biologically active compounds with immunostimulatory properties. The phytochemistry of the M. oleifera revealed high levels of total polyphenol, total phenols, total flavonoids, carotenoids, vitamins C and E.

Dietary Withania sominefera root confers protective and immunotherapeutic effects against Aeromonas hydrophila infection in Nile tilapia (Oreochromis niloticus)

In the present study, effect of dietary Withania sominefera (W. sominefera) root powder was evaluated to modulate immune and antioxidant response against Aeromonas hydrophila (A. hydrophila) infection in Nile tilapia (Oreochromis niloticus). W. sominefera root powder supplemented diets at two concentrations 2.5% (W 2.5%) and 5% (W 5%); fed for 6 weeks prior to the A. hydrophila challenge and continued the same respective diets during the post challenge period (2 weeks). Results showed that fish fed W. sominefera at 5% enhanced immune response in both pre and post-challenge period. NBT level exhibited only significant increase (P < 0.05) in the pre-challenge period compared to control. Malondialdehyde (MDA) levels in liver and muscle revealed significant decrease in both Withania supplemented groups compared to the control in post challenge period. Antioxidant enzymes activities (catalase/CAT/, glutathione S-transferase/GST/, glutathione/GSH; and superoxide dismutase/SOD) were improved in liver and muscle in post challenge period. Glutathione peroxidase (GPx) level in muscle and serum total antioxidant capacity (TAC) showed a significant increase in both Withania supplemented groups compared to the control post challenge. Withania supplementation enhanced disease resistance against A. hydrophila and reduced mortalities (20%), especially at supplemented concentration of 5%. Our findings suggest that W. sominefera root powder may have protective and immunotherapeutic roles in Nile tilapia against A. hydrophila infection which may be useful in controlling important fish bacterial diseases.

Immune responses to methanolic extract of black cumin (Nigella sativa) in rainbow trout (Oncorhynchus mykiss)

The immune stimulating effects of the methanolic extract of black cumin (Nigella sativa) in rainbow trout (Oncorhynchus mykiss) was evaluated. Variable concentrations of black cumin methanolic extract [0 (Control), 0.1 and 0.5 g kg^-1 of feed] were individually added to the basal diet and rainbow trout was fed for 30 days to assess the innate immune responses and growth performance. Feed conversion ratio significantly decreased in the group fed with 0.5 g kg^-1 black cumin extract. Respiratory burst activity was observed to be the highest in the 0.5 g kg^-1 black cumin extract fed group. Lysozyme and myeloperoxidase activities were significantly increased in fish of experimental groups compared to control (P < 0.05). TGF-β gene expression increased in black cumin 0.5 g kg^-1 treated group. IL-1β and TGF-β gene expressions decreased in black cumin 0.1 g kg^-1 administered group. Expression of IL-12 gene diminished in both the experimental groups. There was no significant difference in survival rates between black cumin extract treated fish groups and control (P > 0.05) after challenged with Aeromonas hydrophila. The results indicate that the methanolic extract of black cumin is a stimulator of some innate humoral immune responses, but it is ineffective for cytokine-related gene trancriptions in rainbow trout.

Aloe vera enhances the innate immune response of pacu (Piaractus mesopotamicus) after transport stress and combined heat killed Aeromonas hydrophila infection

In this study, pacu (Piaractus mesopotamicus) were fed with diets containing Aloe vera for 10 days prior to transport stress and infection with heat killed Aeromonas hydrophila. A. vera is popular around the world due to its medicinal properties, including immunostimulatory effects which was observed in this study. The results show that transport causes immunosuppression, an effect that was prevented by A. vera. Specifically, A. vera prevented reductions of both leukocyte respiratory burst and hemolytic activity of complement system caused by transport. Further, fish fed with A. vera also showed significantly higher leukocyte respiratory burst, serum lysozyme concentrations and activity of complement system 24 h after bacterial infection. Additionally, we observed that A. vera may modulate the innate response through activation of complement system during bacterial immune stimulation. In summary, A. vera extract enhanced innate immune parameters and consequently the ability of fish to cope with pathogens following transport stress. These findings show that A. vera has promise for use in aquaculture and add further evidence that medicinal herbs added to fish feed assist to prevent disease outbreaks.

Dietary effect of apple cider vinegar and propionic acid on immune related transcriptional responses and growth performance in white shrimp, Litopenaeus vannamei

This experiment was conducted to study the effect of various levels of ACV^® and Propionic acid (PA) on expression of immune related genes and growth performance in white shrimp (Litopenaeus vannamei). Three hundred and seventy-five shrimps with an average initial weight of 10.2 ± 0.04 g were collected and acclimatized for two weeks. Five experimental diets including control diet, 0.5% PA diet and 1%, 2% and 4% ACV^® diets were applied to feed the shrimps. They were fed 4 times a day with 2.5% of body weight. After 60 days of culture, shrimps fed with ACV^® and PA diets showed no significant difference in growth performance. Expression of prophenoloxidase (proPo), lysozyme (Lys), penaeidin-3a (Pen-3a) and Crustin (Cru) genes were determined from hepatopancreas, using the real-time PCR after 15, 30 and 60 days. Expression of Lys and proPo genes was significantly up regulated in shrimps fed with ACV^® and PA diets compared to the control group after 30 and 60 days of treatment. After 15 days, Pen-3a gene expression was significantly higher in PA group compared to the control group. Also, shrimps fed with 1% and 4% ACV^® and PA diets showed significantly increased expression of Pen-3a after 30 days. In contrast, expression of Cru was significantly down regulated in response to ACV^® diets, but, Cru expression in treated shrimps with PA diet was greater than the control group after 30 and 60 days. Overall, the results provided evidence that ACV^® could be used as a natural immunostimulant for shrimps in order to adjust and enhance expression of the immune related genes.

Effects of local Polynesian plants and algae on growth and expression of two immune-related genes in orbicular batfish (Platax orbicularis)

The emerging orbicular batfish (Platax orbicularis) aquaculture is the most important fish aquaculture industry in French Polynesia. However, bacterial infections are causing severe mortality episodes. Therefore, there is an urgent need to find an effective management solution. Besides the supplying difficulty and high costs of veterinary drugs in French Polynesia, batfish aquaculture takes place close to the coral reef, where use of synthetic persistent drugs should be restricted. Medicinal plants and bioactive algae are emerging as a cheaper and more sustainable alternative to chemical drugs. We have studied the effect of local Polynesian plants and the local opportunistic algae Asparagopsis taxiformis on batfish when orally administered. Weight gain and expression of two immune-related genes (lysozyme g - Lys G and transforming growth factor beta - TGF-β1) were studied to analyze immunostimulant activity of plants on P. orbicularis. Results showed that several plants increased Lys G and TGF-β1 expression on orbicular batfish after 2 and 3 weeks of oral administration. A. taxiformis was the plant displaying the most promising results, promoting a weight gain of 24% after 3 weeks of oral administration and significantly increasing the relative amount of both Lys G and TGF-β1 transcripts in kidney and spleen of P. orbicularis.

Innate immune and growth promoting responses to caper (Capparis spinosa) extract in rainbow trout (Oncorhynchus mykiss)

Cytokine responses, non-specific immune activity and growth promotion effect of dietary caper (Capparis spinosa) supplementation were examined in rainbow trout (Oncorhynchus mykiss). Rainbow trout (12.04 ± 0.71 g) were fed diets containing three doses of caper methanolic extract [0 (Control), 0.1 and 0.5 g kg(-1) of feed] for 30 days. At the end of the feeding trial, expression levels of cytokine genes that included IL-1β, IL-8, TGF-β, IL-12p40, TNF-α1 and IL-10 in head kidney was analyzed using qRT-PCR, and blood and serum were collected to determine superoxide anion production (SAP), phagocytic, lysozyme and myeloperoxidase activities. Expression levels of all cytokines, except TNF-α1 were elevated in the 0.1 g kg(-1) caper extract fed fish group compared to other groups. In 0.5 g kg(-1) caper extract treated fish, only IL-12p40 and IL-10 genes were up-regulated compared to control group fish. SAP was increased in both caper extract treated groups compared to the control, and the highest level was observed in the 0.1 g kg(-1) group. Phagocytic activity in both the caper extract treated groups was increased compared to control with no differences observed between those groups. Lysozyme and myeloperoxidase activities were recorded to be the highest in the 0.1 g kg(-1) fed fish group compared to other groups. Growth promotion was affected positively when caper doses were increased. Survival rate was significantly higher in 0.1 and 0.5 g kg(-1) caper extract treated fish groups compared to control (P < 0.05) after challenged with Aeromonas hydrophila. These results indicate that caper extract stimulates innate immunity through cytokine-mediated responses and promote growth in rainbow trout.

Impact of date palm fruits extracts and probiotic enriched diet on antioxidant status, innate immune response and immune-related gene expression of European seabass (Dicentrarchus labrax)

The application of additives in the diet as plants or extracts of plants as natural and innocuous compounds has potential in aquaculture as an alternative to antibiotics and immunoprophylactics. The aim of the current study was to evaluate the potential effects of dietary supplementation of date palm fruit extracts alone or in combination with Pdp11 probiotic on serum antioxidant status, on the humoral and cellular innate immune status, as well as, on the expression levels of some immune-related genes in head-kidney and gut of European sea bass (Dicentrarchus labrax) after 2 and 4 weeks of administration. This study showed for the first time in European sea bass an immunostimulation in several of the parameters evaluated in fish fed with date palm fruits extracts enriched diet or fed with this substance in combination with Pdp 11 probiotic, mainly after 4 weeks of treatment. In the same way, dietary supplementation of mixture diet has positive effects on the expression levels of immune-related genes, chiefly in head-kidney of Dicentrarchus labrax. Therefore, the combination of both could be considered of great interest as potential additives for farmed fish.

Uncaria tomentosa increases growth and immune activity in Oreochromis niloticus challenged with Streptococcus agalactiae

Cat's claw (Uncaria tomentosa) is an Amazon herb using in native cultures in Peru. In mammals, it has been described several effects of this herb. However, this is the first report of its use on the diet of fish. The aim of this study was to determinate the effect of this plant on the growth and immune activity in Oreochromis niloticus. Nile tilapia (81.3 ± 4.5 g) were distributed into 5 groups and supplemented with 0 (non-supplement fish), 75, 150, 300, and 450 mg of U. tomentosa.kg(-1) of diet for a period of 28 days. Fish were inoculated in the swim bladder with inactivated Streptococcus agalactiae and samples were taken at 6, 24, and 48 h post inoculation (HPI). Dose dependent increases were noted in some of the evaluated times of thrombocytes and white blood cells counts (WBC) in blood and exudate, burst respiratory activity, lysozyme activity, melanomacrophage centers count (MMCs), villi length, IgM by immunohistochemistry in splenic tissue, and unexpectedly on growth parameters. However, dietary supplementation of this herb did not affect red blood cells count (RBC), hemoglobin, and there were no observed histological lesions in gills, intestine, spleen, and liver. The current results demonstrate for the first time that U. tomentosa can stimulate fish immunity and improve growth performance in Nile tilapia.

Innate humoral immune parameters in Tilapia zillii under acute stress by low temperature and crowding

Redbelly tilapia (Tilapia zillii; Gervais, 1848) is one of the most valuable freshwater species in North Africa representing an important part of the continental production, especially in brackish lakes. In Algeria, T. zillii is distributed in several lakes and tributaries of some rivers in the south. Though some attempts are in progress to culture this species, many investigations covering its biology and farm management are still needed. In this sense, this is the first study attempting to evaluate some of the T. zillii immune parameters and valuable data to assess their health and well-being status. Thus, we have determined the levels of serum peroxidases as well as the alternative complement, antiprotease and bactericidal activities. Furthermore, we have also evaluated the potential impact of two acute stress factors, commonly found in fish farms, in these parameters. Although it was assessed that fish exposed to low temperatures or crowding were stressed, as indicated by their increased serum levels of cortisol and glucose, both acute stressors failed to significantly affect serum peroxidases as well as antiprotease and complement activities. However, the bactericidal activity was reduced in general but only in those exposed to crowding reached statistical significance. Further studies are needed to characterise the immune response in T. zillii as well as the effects that farming stresses may produce.

Effects of Prunella vulgaris labiatae extract on specific and non-specific immune responses in tilapia (Oreochromis niloticus)

We examined the effects of Prunella vulgaris Labiatae (P. vulgaris L.) on specific and non-specific immune responses of Nile tilapia, Oreochromis niloticus. The optimal concentration without toxicity of P. vulgaris was determined to 30-40 μg/ml in vitro and 120 μg/100 g of fish in vivo. P. vulgaris significantly elicited an antibody titer compared to FCA or β-glucan. β-glucan plus P. vulgaris group synergistically enhanced antibody production. No significant difference in antibody production was observed between P. vulgaris and P. vulgaris plus β-glucan group. A respiratory burst activity of head kidney (HK) leucocytes of tilapia administered with 300 or 500 μg P. vulgaris was significantly (p < 0.05) enhanced compared with the PBS-injected control group and FCA-treated group. Maximum increase in the NBT reduction value was observed in 500 μg P. vulgaris group but no significant difference was found between 300 and 500 μg P. vulgaris group. The level of serum lysozyme activity was significantly (p < 0.05) higher in the 300 and 500 μg P. vulgaris than 100 μg P. vulgaris and FCA group. The phagocytic activities of HK leucocytes from tilapia administered with 300 and 500 μg P. vulgaris were significantly (p < 0.05) higher than 100 μg P. vulgaris and the control group. P. vulgaris was revealed with a good immunoadjuvant evoking the specific and non-specific immune responses of tilapia.

Acute aerocystitis in Nile tilapia bred in net cages and supplemented with chromium carbochelate and Saccharomyces cerevisiae

Oreochromis niloticus bred in net cages were supplemented with cell wall of Saccharomyces cerevisiae (Sc) (0.3%) or chromium carbochelate (Cr) (18 mg/kg of feed) or in association (Sc + Cr), for 90 days. After this period, acute inflammation was induced in the swim bladder by inoculation of 3 × 10(8) CFU of inactivated Streptococcus agalactiae, and another group received 0.65% saline solution (control). Twelve, 24, and 48 h after stimulation, the inflammation was evaluated through total and differential counting of accumulated cells, and through leukocyte respiratory burst in the blood, cortisolemia, glycemia and serum lysozyme concentration. The results showed that there were greater total numbers of cells in the exudate of fish inoculated with inactivated bacterium than in those injected with saline solution, with predominance of lymphocytes, thrombocytes, macrophages and granulocytes. Tilapia supplemented with Cr presented increased total numbers of cells with significant accumulation of lymphocytes and reductions in cortisolemia and glycemia, but the different treatments did not have any influence on leukocyte respiratory burst or serum lysozyme concentration. Tilapia supplemented with Sc and the Cr + Sc association did not present significant changes to the variables evaluated, despite higher accumulation of lymphocytes in the inflammatory exudate from fish treated with Sc. The results indicate that tilapia bred in net cages and supplemented with Cr presented higher total accumulation of cells at the inflammatory focus, thus indicating an increase in the inflammatory response induced by the bacterium, probably due to the reduction in cortisolemia and higher glucose consumption. Thus, supplementation with Cr had beneficial action, which facilitated development of acute inflammation induced by the bacterium, but did not affect neither leukocyte respiratory burst in the blood nor serum lysozyme concentration.