Systems-thinking approach to identify and assess feasibility of potential interventions to reduce antibiotic use in tilapia farming in Egypt

Antibiotics are used in aquaculture to maintain the health and welfare of stocks; however, the emergence and selection of antibiotic resistance in bacteria poses threats to humans, animals and the environment. Mitigation of antibiotic resistance relies on understanding the flow of antibiotics, residues, resistant bacteria and resistance genes through interconnecting systems, so that potential solutions can be identified and issues around their implementation evaluated. Participatory systems-thinking can capture the deep complexity of a system while integrating stakeholder perspectives. In this present study, such an approach was applied to Nile tilapia (Oreochromis niloticus) production in the Nile Delta of Egypt, where disease events caused by antibiotic-resistant pathogens have been reported. A system map was co-produced with aquaculture stakeholders at a workshop in May 2018 and used to identify hotspots of antibiotic use, exposure and fate and to describe approaches that would promote fish health and thus reduce antibiotic use. Antibiotics are introduced into the aquaculture system via direct application for example in medicated feed, but residues may also be introduced into the system through agricultural drainage water, which is the primary source of water for most fish farms in Egypt. A follow-up survey of stakeholders assessed the perceived feasibility, advantages and disadvantages of potential interventions. Interventions that respondents felt could be implemented in the short-term to reduce antibiotic usage effectively included: more frequent water exchanges, regular monitoring of culture water quality parameters, improved storage conditions for feed, use of probiotics and greater access to farmer and service providers training programmes. Other potential interventions included greater access to suitable and rapid diagnostics, high quality feeds, improved biosecurity measures and genetically-improved fish, but these solutions were expected to be achieved as long-term goals, with cost being of one of the noted barriers to implementation. Identifying feasible and sustainable interventions that can be taken to reduce antibiotic use, and understanding implementation barriers, are important for addressing antibiotic resistance and ensuring the continued efficacy of antibiotics. This is vital to ensuring the productivity of the tilapia sector in Egypt. The approach taken in the present study provides a means to identify points in the system where the effectiveness of interventions can be evaluated and thus it may be applied to other food production systems to combat the problem of antibiotic resistance

Use of different Saccharomyces cerevisiae biotic forms as immune-modulator and growth promoter for Oreochromis niloticus challenged with some fish pathogens

The manipulation of intestinal bacterial flora through dietary supplementation of beneficial microbes is a new approach not only from the nutrition point of view but also to overcome the adverse effects of chemotherapeutants and lack of effective vaccines. The current study was performed to assess the role of Saccharomyces cerevisiae as a whole yeast cell (Probiotic), its extract (mannan-oligosaccharide - Prebiotic) and Pre-Probiotic mixture (Synbiotic) as growth promoters and immunostimulants in cultured Oreochromis niloticus (O. niloticus). One hundred fifty-six O. niloticus were divided into four groups fed on Probiotic, Prebiotic, synbiotic and basal diet for two months. Treated fish groups showed significant improvement in growth performance and activation of non-specific cellular/humoral immunological measures together with a relative enhancement of resistance against challenged bacteria. Synbiotic feed additive has proved significant enhancement of fish innate resistance against selected fish pathogens as well as positively increased the growth performance of challenged fish

Monitoring of different vibrio species affecting marine fishes in Lake Qarun and Gulf of Suez: Phenotypic and molecular characterization

Vibriosis is a globally threatening bacterial disease affecting mariculture with high mortalities and severe economic losses. Isolation and Identification of different vibrio species were performed to a total number of one hundred moribund and freshly dead Solea aegyptiaca, Epinephelus marginatus and Mugil cephalus collected from Lake Qarun and Gulf of Suez. Phenotypic picture and molecular identification based on use of 16SrRNA gene sequence confirmed 44 strains as vibrio species. Further molecular identification of retrieved vibrio spp. using species specific primers for collagenase, ToxR and Vvh genes categorized 10 isolates belong to V. alginolyticus, 8 isolates belong to V. parahaemolyticus and 6 isolates belong to V. vulnificus. The total prevalence of vibriosis was 44% where the highest prevalence was recorded in Lake Qarun examined fishes

Efficacy of dietary yeast cell wall supplementation on the nutrition and immune response of Nile tilapia

Prebiotics are non-digestible carbohydrates that improve the animal health via modulation of their intestinal beneficial organisms. Immunowall® is a commercial prebiotic consists of high concentration of yeast β-glucan (βG) and Mannan-oligosaccharides (MOS). The current study was designed to investigate the prebiotic potential of Immunowall® on nutrition and health performance of Nile tilapia Oreochromis niloticus. Three fish groups were nourished on control diet supplemented with 0%, 0.1% and 0.2% Immunowall® for two months. Both dietary levels of Immunowall® exhibited significant increase in growth parameters (P ≤ 0.05) as well as in white blood cell count, total protein, and globulin concentrations. While, the immune parameters such as antioxidant biomarkers (catalase and glutathione-reductase), non-specific immune response (e.g. phagocytic activity, phagocytic index and lysozyme activity) and immune-related genes expressions (e.g. TNF-α and IL-1β) were higher in 0.2% Immunowall® compared to 0.1% Immunowall® and control. Oral administration of β-glucan and MOS mixture reduced the mortalities after microbial infections with L. gravieae and A. hydrophila. Therefore, we can recommend the dietary inclusion of Immunowall® in aqua-feed as an efficient method to achieve feasible and sustainable fish production. Keywords: β-Glucan, MOS, Immunity, Growth, Challenge, Nile tilapi

Neem leaf powder (Azadirachta indica) mitigates oxidative stress and pathological alterations triggered by lead toxicity in Nile tilapia (Oreochromis niloticus)

Abstract This study investigated the clinical and pathological symptoms of waterborne lead toxicity in wild Nile tilapia collected from a lead-contaminated area (the Mariotteya Canal: Pb = 0.6 ± 0.21 mg L−1) and a farmed fish after 2 weeks of experimental exposure to lead acetate (5–10 mg L−1) in addition to evaluating the efficacy of neem leaf powder (NLP) treatment in mitigating symptoms of lead toxicity. A total of 150 fish (20 ± 2 g) were alienated into five groups (30 fish/group with three replicates). G1 was assigned as a negative control without any treatments. Groups (2–5) were exposed to lead acetate for 2 weeks at a concentration of 5 mg L−1 (G2 and G3) or 10 mg L−1 (G4 and G5). During the lead exposure period, all groups were reared under the same conditions, while G3 and G5 were treated with 1 g L−1 NLP. Lead toxicity induced DNA fragmentation and lipid peroxidation and decreased the level of glutathione and expression of heme synthesis enzyme delta aminolaevulinic acid dehydratase (ALA-D) in wild tilapia, G2, and G4. NLP could alleviate the oxidative stress stimulated by lead in G3 and showed an insignificant effect in G5. The pathological findings, including epithelial hyperplasia in the gills, edema in the gills and muscles, degeneration and necrosis in the liver and muscle, and leukocytic infiltration in all organs, were directly correlated with lead concentration. Thus, the aqueous application of NLP at 1 g L−1 reduced oxidative stress and lowered the pathological alterations induced by lead toxicity

A First Report of Molecular Typing, Virulence Traits, and Phenotypic and Genotypic Resistance Patterns of Newly Emerging XDR and MDR <i>Aeromonas veronii</i> in <i>Mugil seheli</i>

Aeromonas veronii is associated with substantial economic losses in the fish industry and with food-borne illness in humans. This study aimed to determine the prevalence, antibiogram profiles, sequence analysis, virulence and antimicrobial resistance genes, and pathogenicity of A. veronii recovered from Mugil seheli. A total of 80 fish were randomly gathered from various private farms in Suez Province, Egypt. Subsequently, samples were subjected to clinical, post-mortem, and bacteriological examinations. The retrieved isolates were tested for sequence analysis, antibiogram profile, pathogenicity, and PCR detection of virulence and resistance genes. The prevalence of A. veronii in the examined M. seheli was 22.5 % (18/80). The phylogenetic analyses revealed that the tested A. veronii strains shared high genetic similarity with other A. veronii strains from India, UK, and China. Using PCR it was revealed that the retrieved A. veronii isolates harbored the aerA, alt, ser, ompAII, act, ahp, and nuc virulence genes with prevalence of 100%, 82.9%, 61.7%, 55.3%, 44.7%, 36.17%, and 29.8%, respectively. Our findings revealed that 29.8% (14/47) of the retrieved A. veronii strains were XDR to nine antimicrobial classes and carried blaTEM, blaCTX-M, blaSHV,tetA, aadA1, and sul1 resistance genes. Likewise, 19.1% (9/47) of the obtained A. veronii strains were MDR to eight classes and possessed blaTEM, blaCTX-M, blaSHV,tetA, aadA1, and sul1 genes. The pathogenicity testing indicated that the mortality rates positively correlated with the prevalence of virulence-determinant genes. To our knowledge, this is the first report to reveal the occurrence of XDR and MDR A. veronii in M. seheli, an emergence that represents a risk to public health. Emerging XDR and MDR A. veronii in M. seheli frequently harbored aerA, alt, ser, ompAII, and act virulence genes, and blaTEM, sul1, tetA, blaCTX-M, blaSHV, and aadA1 resistance genes

Analysis of the Productivity, Immunity, and Health Performance of Nile Tilapia (Oreochromis niloticus) Broodstock-fed Dietary Fermented Extracts Sourced from Saccharomyces cerevisiae (Hilyses): A Field Trial

The present study aimed to evaluate the effect of dietary fermented extracts sourced from Saccharomyces cerevisiae (nucleotides, β-glucans and MOS) (Hilyses®) on the production and health of Nile tilapia (Oreochromis niloticus) broodstock, as well as on seed survival and performance. The trial was performed in a hatchery along the spawning season and continued in the laboratory to monitor the performance in fry and fingerlings. The broodstock were divided into two groups, (C) fed a basal diet and (H) fed 0.4% Hilyses. Blood and histological parameters, antioxidant power, cortisol level and the expression of some immune-related (TLR-2, IL-1β and TNF-α) and growth-related genes (MUC-2 and IGF-1) were measured. The obtained seeds were subdivided into four treatments: (C-C) fed a basal diet, (C-H) fed 0.4% Hilyses, (H-C) fed a basal diet and (H-H) fed 0.4% Hilyses. Results revealed that the dietary inclusion of Hilyses in the broodstock increased seed production, survival, hematological parameters, and antioxidant power. Moreover, it improved the intestinal microstructure and upregulated the immune- and growth-related genes. The growth indices of fry and fingerlings were significantly increased in all Hilyses-treated groups (p &lt; 0.05). The performance in the (H-H) group significantly surpassed those of all groups. Therefore, dietary fermented yeast could be used as a strategic solution to sustain tilapia production