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Aeromonas spp. are opportunistic pathogens which cause diseases in ornamental fish. But the degree of infection and the severity of disease caused by various Aeromonas spp. are generally being reported to be strain specific. Therefore, the present study focused on the disease induction ability of previously isolated Aeromonasveronii XhG1.2 in Xiphophorushellerii in comparison with A. hydrophila (MTCC 1739). Further, the ability of A. veronii XhG1.2 to cause disease in other selected ornamental fish such as Poeciliasphenops (molly), Carassiusauratus (goldfish) and Cyprinuscarpio (common carp) has also been studied. Here, the intramuscular injection of A. veronii XhG1.2 was observed to cause disease incidence and increased mortality in all the selected ornamental fish. The mortality observed was 100, 100 and 88.3%, respectively, for P. sphenops, C. auratus and C. carpio within the 48‐h period. Histopathological analysis of gill, liver and intestine of all the XhG1.2 treated fish further confirmed its role in fish disease. The results of the study are indicative of emergence of Aeromonas spp. with the ability to cause disease in wide range of ornamental fish. [ABSTRACT FROM AUTHOR]

The use of essential oils (EOs) is a promising strategy for reducing antibiotic use in aquaculture. In this study, we investigated the chemical composition, in vitro cytotoxicity and antimicrobial activity of 16 commercial plant‐derived EOs against Aeromonas hydrophila,A. jandaei and Citrobacter freundii isolated from diseased freshwater fish (Oreochromis niloticus and Pterophyllum scalare). Efficacy of treatment with EOs and four antibiotics used in aquaculture: enrofloxacin, florfenicol, oxytetracycline and thiamphenicol, were compared. The chemical compositions of EOs were determined via high‐resolution gas chromatography, and the in vitro cytotoxicity and antimicrobial activity were assessed using a haemolysis assay and the microdilution method respectively. Ninety‐four components of EOs were identified. The principal components of most EOs were oxygenated monoterpene hydrocarbons. Most EOs possessed non‐cytotoxic effects against fish erythrocytes at concentrations with strong (MIC ≤ 500 µg/ml) and moderate (600 µg/ml ≤ MIC ≤1,500 µg/ml) antimicrobial activity. A. sativum, C. verum, O. basilicum, S. aromaticum and T. vulgaris EOs were the most active against microbial strains assessed. The present study highlights the potential of using EO to control bacterial disease in cultured fish. [ABSTRACT FROM AUTHOR]

This study aimed to evaluate the current status on the use of probiotics, disinfectants and antimicrobials in hatcheries, nurseries and grow-out farms producing Pangasius catfish ( Pangasianodon hypophthalmus) in the Mekong Delta, Vietnam. Semi-structured interviews were conducted with 83 aquaculture enterprises (15 hatcheries, 32 nurseries and 36 grow-out farms). Farmers reported use of a total of 24 different antimicrobials, e.g. for treatment of bacillary necrosis and motile aeromonad septicaemia, and a variety of disinfectants, probiotics and nutritional supplements. In contrast to small-scale farmers, all large-scale grow-out farmers studied were certified and therefore had higher levels of formal education and specialized aquaculture training to diagnose and treat diseases. All farmers prepared their own medicated feed with a high risk of treatment failure, negative environmental impact from released antimicrobials and resistance development. Small-scale farmers were at particular occupational health risks when handling antimicrobials and other chemicals, e.g. mixing medicated feed with bare hands. There is an urgent need to improve knowledge and use innovative approaches, e.g. private-public partnerships, to assure a prudent use of chemicals, to improve capacity and access to disease diagnosis, particularly for small-scale grow-out farmers and nurseries. Efforts to control use of antimicrobials in aquaculture should be coordinated with the livestock and human health sectors taking an One-Health approach. [ABSTRACT FROM AUTHOR]

This study investigated the effects of levan produced by Bacillus licheniformis FRI MY-55 on growth performance, intestinal count of viable bacteria, immune status, pathogen resistance and body composition of orange-spotted grouper ( Epinephelus coioides). Orange-spotted grouper were fed diets supplemented with levan at concentrations of 0 (control), 5.0, 10.0, 25.0 and 50.0 g kg−1 for 12 weeks. The final weight and per cent weight gain were significantly higher in the 25.0 g kg−1 levan-supplemented group than in the control group ( p < 0.05). All levan-supplemented diets significantly decreased the count of total viable aerobic bacteria and Vibrio spp. in the intestines of groupers ( p < 0.05). Serum total protein levels, globulin levels, lysozyme activity and survival rate of orange-spotted grouper after challenge with V. harveyi were significantly higher in the 25.0 g kg−1 levan-supplemented group than in the control group ( p < 0.05). This study also found that the 10.0, 25.0 and 50.0 g kg−1 levan-supplemented diets significantly increased the crude protein level in the body composition of orange-spotted grouper. Overall, the results of this study indicate that dietary levan (25.0 g kg−1) could be an effective method for enhancing the growth performance and disease resistance in orange-spotted grouper. [ABSTRACT FROM AUTHOR]

In spring of 2011, an epidemic outbreak of torafugu with high mortality occurred in an aquafarm with marine industrial recirculation aquaculture system ( MIRAS) in Yantai, Shandong Province, China. The diseased fish showed anorexia, haemorrhaging and festering fin and skin and swelling internal organs. Forty-five dominant bacterial isolates were obtained from the diseased fish, and were found to belong to 12 species according to 16S r RNA gene sequences. One strain from each species was selected to test the pathogenicity, and five strains were showed to be virulent to zebrafish. Whereas Enterovibrio nigricans Fr42 was highly virulent with the LD50 of 7.8 × 104 CFU g−1, Photobacterium swingsii Fr23, Vibrio owensii Fr40, V. harveyi Fr51 and V. rotiferianus Fr71 were moderately virulent with the LD50 of 1.7 × 106 to 8.4 × 106 CFU g−1. Both the bacteria and their extracellular products of the five strains were found to show phospholipase, caseinase, gelatinase, amylase and/or lipase activities. The production of N-acyl homoserine lactones ( AHLs) of the five strains was detected by three different AHLs biosensors, and three of them were found to produce AHLs by at least one kind of biosensor. This is the first study describing various opportunistic bacterial pathogens of fish cultured in MIRAS in China. [ABSTRACT FROM AUTHOR]

Ambient water temperature is a key factor controlling the distribution and impact of disease in fish populations, and optimum temperature ranges have been characterised for the establishment of a number important aquatic diseases exotic to the UK. This study presents a simple regression method to approximate daily average surface water temperature in lakes of 0.5-15 ha in size across the UK using 5 km2 gridded daily average air temperatures provided by the UK Meteorological Office. A Geographic information system (GIS) is used to present thematic maps of relative risk scores established for each grid cell based on the mean number of days per year that water temperature satisfied optimal criteria for the establishment of two economically important pathogens of cyprinid fish (koi herpesvirus (KHV) and spring viraemia of carp virus (SVCV)) and the distribution and density of fish populations susceptible to these viruses. High-density susceptible populations broadly overlap the areas where the temperature profiles are optimal for KHV (central and south-east England); however, few fish populations occur in areas where temperature profiles are most likely to result in the establishment of spring viremia of carp (SVC) (namely northern England and Scotland). The highest grid-cell risk scores for KHV and SVC were 7 and 6, respectively, out of a maximum score of 14. The proportion of grid cells containing susceptible populations with risk scores of 5 or more was 37% and 5% for KHV and SVC, respectively. This work demonstrates a risk-based approach to inform surveillance for exotic pathogens in aquatic animal health management, allowing efficient use of resources directed towards higher risk animals and geographic areas for early disease detection. The methodology could be used to examine the change in distribution of high-risk areas for both exotic and endemic fish diseases under different climate change scenarios. [ABSTRACT FROM AUTHOR]

We attempted to develop an ultrahigh sensitive method for detecting Flavobacterium psychrophilum using high-gradient immunomagnetic separation (HGIMS) with a polymerase chain reaction (PCR). HGIMS is a magnetic separation method in which the magnetic force is strengthened by introducing a magnetic gradient between the magnetic filter and nearby column. Because immunomagnetic beads specifically react with target cells, target cells are collected efficiently. Accumulated beads are released from the filter by removing the external magnetic force. After concentrating the samples using the HGIMS system, DNA was extracted from the samples, and PCR was applied to detect F. psychrophilum. Our primers did not react with reference bacteria and reacted specifically with F. psychrophilum. The detection sensitivity using the HGIMS system was higher than that of the method without the HGIMS system, and the total assay time, including sample preparation, was <3.5 h. PCR products of the expected size were obtained from samples of concentrated 4 × 10−1 to 4 × 103 cfu mL−1 F. psychrophilum more than 80% of the time using the HGIMS system. Furthermore, our proposed method could be useful for the specific detection of F. psychrophilum from actual samples. Our proposed method is suitable for the highly sensitive detection of F. psychrophilum. [ABSTRACT FROM AUTHOR]

The application of biotechnology in aquaculture has enabled the development and improvement of a wide range of immunodiagnostic and molecular technologies, and reagents and commercial kits have become more generally available. Recently, method development has increased exponentially as techniques used for clinical and veterinary medicine are adapted and optimized for use in aquaculture. Careful consideration needs to be given to selecting which rapid diagnostic methods to take forward and apply in aquaculture - pathogen detection methods need to be robust yet sensitive, and in many cases, capable of detecting a high degree of heterogeneity. There are numerous innovative techniques that may fulfil these criteria and provide valuable diagnostic tools. It is also important, however, that useful diagnostic methods already developed are standardized and fully validated, and that new technologies do not supercede these just because they are novel methods. The cost, speed, specificity and sensitivity of assays are all extremely important to end-users. This paper looks at some of the opportunities and challenges for the development of rapid diagnostics for aquaculture. [ABSTRACT FROM AUTHOR]

The article offers information on the fish disease called furunculosis. It states that the disease is caused due to Aeromonas salmonicida and raises the mortality rate upto 90 percent, causing economical losses in hatcheries. It mentions that the host for the disease is increasing which includes brown trout, Atlantic salmon and brook trout.