clay and Fish-Diseases

The effect of Sodium Bentonite (SB) enriched diet on growth performance, innate immune response, and disease resistance in stinging catfish, Heteropneustes fossilis against Aeromonas hydrophila is reported. The infected fish fed with 5% SB had the maximum weight gain diet (PWG %) and specific growth rate (SGR %) were 26% and 29% when compared to 14% and 17% with 10% diet. Similarly the phagocytic activity increased significantly when infected fish were fed with 5% or 10% SB diets during the experimental period; the complement, respiratory burst and lysozyme activities were also significantly enhanced on weeks 2 and 4. The lower cumulative mortality (10% and 15%) was observed when the infected fish were fed with 5% and 10% SB diets for 30 days. The results suggest that the infected H. fossilis after administration of 5% and 10% SB enriched diets for 30 days had significantly improved growth performance, innate immunity, and disease resistance against A. hydrophilla. Hence, sodium bentonite can be used as a feed additive to stimulate immunity and for disease resistance in the effective production of economically valuable freshwater catfish, H. fossilis.

Topics: Aeromonas hydrophila; Aluminum Silicates; Animal Feed; Animals; Bentonite; Catfishes; Clay; Diet; Dietary Supplements; Disease Resistance; Fish Diseases; Gram-Negative Bacterial Infections; Immunity, Innate

The use of antibiotics in aquaculture raises environmental and food safety concerns because chronic exposure of an aquatic ecosystem to antibiotics can result in the spread of antibiotic resistance, bioaccumulation of antibiotics in the organisms, and transfer of antibiotics to humans. In an attempt to overcome these problems, high-concentration red clay was applied as an alternative antibiotic against the following common fish pathogens: Aeromonas salmonicida, Vibrio alginolyticus, and Streptococcus equinus. The growth of A. salmonicida and V. alginolyticus was retarded by red clay, whereas that of S. equinus was promoted. Phase contrast and scanning electron microscopy analyses confirmed the attachment of red clay on cell surfaces, resulting in rapid gravitational removal and cell surface damage in both A. salmonicida and V. alginolyticus, but not in S. equinus. Different cell wall properties of grampositive species may explain the unharmed cell surface of S. equinus. Significant levels of oxidative stress were generated in only the former two species, whereas significant changes in membrane permeability were found only in S. equinus, probably because of its physiological adaptation. The bacterial communities in water samples from Oncorhynchus mykiss aquacultures supplemented with red clay showed similar structure and diversity as those from oxytetracycline-treated water. Taken together, the antibiotic effects of high concentrations of red clay in aquaculture can be attributed to gravitational removal, cell surface damage, and oxidative stress production, and suggest that red clay may be used as an alternative for antibiotics in aquaculture.

Topics: Aeromonas salmonicida; Aluminum Silicates; Animals; Anti-Bacterial Agents; Clay; Fish Diseases; Oncorhynchus mykiss; Streptococcus; Vibrio alginolyticus; Water Microbiology

Columnaris disease, caused by the bacterial pathogen Flavobacterium columnare, continues to be a major problem worldwide in both wild and cultured freshwater finfish. Despite the far-reaching negative impacts of columnaris disease, safe and efficacious preventatives and curatives for this disease remain limited. In this study, we evaluated the potential of kaolin (Al2 Si2 05 (OH)4 ), a type of clay, for the prevention of columnaris disease. Channel catfish, Ictalurus punctatus (Rafinesque), fingerlings were experimentally challenged with Flavobacterium columnare in untreated water or with water containing kaolin (1 g L(-1) ). Over the 7-day course of study, kaolin treatment led to significantly (P < 0.001) improved survival (96%) as compared to untreated fish (78% survival). Histological examination of the gills revealed that kaolin-treated fish had substantially less gill damage than untreated controls. Quantitative PCR analysis of gill tissue revealed that kaolin significantly reduced F. columnare adhesion (measured at 1 h post-challenge) and colonization (24 h post-challenge). Incubation of kaolin with F. columnare in vitro demonstrated that kaolin reduced the number of F. columnare cells in culture supernatants, presumably through the formation of physical complexes through adsorption. In summary, kaolin can improve survival, reduce gill pathologies and reduce bacterial attachment to key tissues associated with columnaris disease in channel catfish by binding to F. columnare.

Topics: Aluminum Silicates; Animals; Bacterial Adhesion; Clay; Fish Diseases; Flavobacteriaceae Infections; Flavobacterium; Gills; Ictaluridae; Survival Analysis