bassianolide and Flavobacteriaceae-Infections

Good knowledge on the disease situation and its impact on production is a base mechanism for designing health surveillance, risk analysis and biosecurity systems. Mediterranean marine fish farming, as any aquaculture production, is affected by various infectious diseases. However, seabass and seabream, the main produced species, are not listed as susceptible host species for the notifiable pathogens listed in the current EU legislation, which generates a lack of systematic reporting. The results presented in this study come from a survey directly to fish farms (50 hatchery and on-growing units from 10 Mediterranean countries), with data from 2015 to 2017, conducted by the H2020 project MedAID. Seabass showed a higher survival rate (85%) through a production cycle than seabream (80%) in spite of equal mortality due to pathogen infections (10%). The differences in survival may be explained by mortality 'of other causes'. Seabream and seabass have different disease profiles, and the profile is slightly different between geographical regions. Among the most important diseases, tenacibaculosis and vibriosis were identified in seabass and Sparicotyle chrysophrii (a gill fluke) and nodavirus in seabream. Correlating mortality data to management variables showed that increasing density, buying fingerlings from external sources and treatments due to disease are factors that negatively influence mortality rate. Most of the surveyed farms did not keep sufficient quality data to implement good health status reports and perform detailed impact studies, which shows the necessity of updating the current legislative framework to provide the basis for better reporting of relevant pathogens in the Mediterranean basin.

Topics: Animals; Aquaculture; Bass; Fish Diseases; Fisheries; Flavobacteriaceae Infections; Mediterranean Region; Sea Bream; Surveys and Questionnaires; Vibrio Infections

Flavobacterium columnare is an aquatic bacterium that is responsible for columnaris disease. This aquatic pathogen has a worldwide distribution and is highly infectious to both warm and cold water fish. A modified live F. columnare vaccine was developed by repeated passage of a virulent strain on increasing concentrations of rifampicin that resulted in attenuation. Here we report vaccination/challenge trials to evaluate efficacy and safety. In separate laboratory trials, immersion vaccination of channel catfish (Ictalurus punctatus) fry between 10 to 48 days post hatch (DPH) with experimental vaccine or licensed product resulted in relative percent survival (RPS) between 57-94% following challenge. Similarly, a vaccination/challenge trial using largemouth bass (Micropterus salmoides) fry at 10 DPH was performed using various doses of licensed product under laboratory conditions. Results demonstrated safety of the vaccine and significant protection following challenge with RPS values between 74-94%, depending on vaccine dose. Together, these trials demonstrate the vaccine administered to early life-stage channel catfish and largemouth bass is safe and reduces mortality following challenge with F. columnare.

Topics: Animals; Bacterial Vaccines; Bass; Fish Diseases; Flavobacteriaceae Infections; Flavobacterium; Ictaluridae

Columnaris disease generates substantial losses of many freshwater fish species; one is the hybrid striped bass. The ubiquitous aquatic bacterium Flavobacterium columnare can be highly effective in biofilm formation on fish skin and gills. Previous research showed a difference between columnaris disease susceptibility of hybrid striped bass (Morone saxatilis × M. chrysops) and white bass (M. chrysops). To understand these differential susceptibilities and possible mucosal relationship, we assessed total bacterial growth and biofilm formation with mucus derived from each moronid parental species: white bass and striped bass (M. saxatilis). Differential susceptibility was confirmed of the other parent species, the striped bass (M. saxatilis). In addition to intraspecies investigations, individual hybrid striped bass mucosal affects were also studied for deferential responses to bacterial growth and biofilm formation. Species- and concentration-dependent differences were detected in the total growth of the bacteria to host mucus. Our data suggest that bass mucus can significantly affect biofilm formation with the F. columnare isolate tested. There appears to be a correlation between the bacteria's response of growth and biofilms and bass species susceptibility. This study provides insight into our understanding of the host-pathogen interaction between F. columnare and moronids.

Topics: Animals; Bass; Biofilms; Fish Diseases; Flavobacteriaceae Infections; Flavobacterium; Gills; Mucus

Outbreaks of diseases in farmed fish remain a recurring problem despite the development of vaccines and improved hygiene standards on aquaculture farms. One commonly observed bacterial disease in tropical aquaculture of the South-East Asian region is tenacibaculosis, which is attributed to members of the genus Tenacibaculum (family Flavobacteriaceae, phylum Bacteroidetes), most notably Tenacibaculum maritimum. The impact of tenacibaculosis on the fish microbiota remains poorly understood. In this study, we analysed the microbiota of different tissues of commercially reared Asian seabass (Lates calcarifer) that showed symptoms of tenacibaculosis and compared the microbial communities to those of healthy and experimentally infected fish that were exposed to diseased farmed fish. The relative abundance of Tenacibaculum species in experimentally infected fish was significantly lower than in commercially reared diseased fish and revealed a higher prevalence of different Tenacibaculum species. One isolated strain, TLL-A2

Topics: Animals; Aquaculture; Bass; Fish Diseases; Fishes; Flavobacteriaceae; Flavobacteriaceae Infections; Genes, Bacterial; Genome, Bacterial; Microbiota; Perciformes; Phenotype; Phylogeny; RNA, Ribosomal, 16S; Tenacibaculum

Four Gram-negative bacterial isolates were recovered from 2 disease outbreaks that occurred in 2013 affecting European sea bass Dicentrarchus labrax fry and sea bream Sparus aurata adults. Main symptoms were erratic swimming, eroded fins and, in the sea bream outbreak, haemorrhages on the body surface; bacteria were always recovered from internal organs, almost in pure culture. On the basis of phenotypic characterization and 16S rRNA gene sequence analysis, the isolates were identified as Lacinutrix venerupis, a bacterium not previously reported as a fish pathogen. The highest 16S rDNA sequence similarities were recorded with the type strain of this species (99.9-100% similarity), while other species showed similarities below 97%, the closest relative being L. mariniflava (96.3% similarity). Phenotypic characterization showed some discrepancies with the L. venerupis type strain (mainly in BIOLOG GN profile); however, DNA-DNA hybridization assays with L. venerupis and L. mariniflava type strains confirmed that these isolates belong to the former species (levels of DNA relatedness were 98-100% and 38-50%, respectively). Finally, a virulence evaluation of the isolates using Senegalese sole Solea senegalensis fry was also performed; significant mortalities (80-100% mortality within 4 d) were recorded after intraperitoneal injection, but only with high doses of bacteria (107colony forming units fish-1). Further studies will be necessary to determine the importance of this species as a fish pathogen.

Topics: Animals; Bass; Disease Outbreaks; DNA, Bacterial; Fish Diseases; Flavobacteriaceae; Flavobacteriaceae Infections; Phylogeny; Sea Bream

Hybrid striped bass (HSB) and white bass (WB) were evaluated for their susceptibility to Flavobacterium columnare, the causative agent of columnaris disease, in 3 fundamental studies. In the first experiment, we determined whether columnaris disease could be developed by experimental challenge in HSB. This challenge consisted of 3 levels of F. columnare (10, 30, and 60 ml volumes) determined to be 2.25 × 10(7), 6.75 × 10(7), and 1.35 × 10(8) CFU ml(-1), respectively. Each treatment group exhibited significantly different survival rates: 0, 3.3, and 13.3% in the 60, 30, and 10 ml groups, respectively. In Expt 2, using the 30 ml dose, both HSB and WB had a 0% survival rate, with WB taking significantly longer to reach 100% mortality. In Expt 3, using the 10 ml dose, no HSB survived, whereas 33% of WB survived (p < 0.0001). Compared to controls, HSB treated with 10 ml showed extensive gill damage at 24 h, which could have contributed to the higher mortality observed in HSB; in contrast, WB gills showed noticeably less damage. From these series of experiments, it is clear that HSB are more sensitive to F. columnare, having lower survival and more extensive histological damage compared to WB following challenge.

Topics: Animals; Bass; Crosses, Genetic; Fish Diseases; Flavobacteriaceae Infections; Flavobacterium; Genetic Predisposition to Disease; Gills

A novel Gram-stain-negative rod-shaped gliding bacterial strain, designated 35/09(T), was isolated from diseased European sea bass (Dicentrarchus labrax L.) in Spain. Colonies were pale-yellow-pigmented with uneven edges and did not adhere to the agar. The DNA G+C content of the isolate was 31.3 mol%. 16S rRNA gene sequence analysis indicated affiliation to the genus Tenacibaculum (family Flavobacteriaceae, phylum 'Bacteroidetes'). Sequence similarities between the isolate and type strains of other members of the genus were 93.1-97.3 %. The major fatty acids (>5 % of the total fatty acids) were iso-C(15 : 0) (24.8 %), iso-C(15 : 0) 3-OH (18.0 %), anteiso-C(15 : 0) (8.1 %), C(15 : 1)ω6c (6.9 %) and iso-C(15 : 1) (6.2 %). Genotypic and phenotypic data indicate that strain 35/09(T) should be classified as a representative of a novel species in the genus Tenacibaculum, for which the name Tenacibaculum dicentrarchi sp. nov. is proposed; the type strain is 35/09(T) ( = CECT 7612(T) = NCIMB 14598(T)).

Topics: Animals; Bacterial Typing Techniques; Base Composition; Bass; DNA, Bacterial; DNA, Ribosomal; Fatty Acids; Fish Diseases; Flavobacteriaceae Infections; Genes, rRNA; Genotype; Molecular Sequence Data; Phenotype; Phylogeny; RNA, Ribosomal, 16S; Sequence Analysis, DNA; Spain; Tenacibaculum

Topics: Animals; Aquaculture; Bass; Fish Diseases; Flavobacteriaceae Infections; Greece; Phylogeny; Sea Bream; Tenacibaculum

Two experiments were conducted to test the effectiveness of different therapeutants against a mixed infection of Aeromonas hydrophila and Flavobacterium columnare in sunshine bass. Experiment 1 evaluated copper sulphate, florfenicol-medicated feed and potassium permanganate (KMnO(4) ) against a natural mixed infection. Experiment 2 further evaluated copper sulphate as a treatment to control an experimental mixed infection. In experiment 1, naturally infected untreated fish had the lowest final survival per cent, at 71%, while florfenicol-medicated feed at 15mgkg(-1) body weight for 10days or copper sulphate at 2.1mgL(-1) (1% of the total alkalinity) for 24h produced the highest final survivals, at 90% and 88%, respectively. The final survival of the naturally infected fish administered florfenicol-medicated feed was significantly different (P<0.1) from the untreated fish. The survival curves for the florfenicol and the copper sulphate at 2.1mgL(-1) were significantly improved from the untreated fish. In experiment 2, fish were challenged by waterborne exposure to A. hydrophila and F. columnare and either not treated or treated with copper sulphate at 2.1mgL(-1) . At the end of experiment 2, the per cent survival of the challenged fish treated with copper sulphate (99%) was significantly higher (P<0.05) than the non-treated (61%). The results illustrate clear benefit of florfenicol and copper sulphate against a mixed infection of A. hydrophila and F. columnare.

Topics: Aeromonas hydrophila; Animals; Anti-Bacterial Agents; Bass; Coinfection; Copper Sulfate; Female; Fish Diseases; Flavobacteriaceae Infections; Flavobacterium; Gram-Negative Bacterial Infections; Male; Potassium Permanganate; Treatment Outcome

Vaccinated, feed-trained largemouth bass fry (Micropterus salmoides floridanus) were cohabited with sham-vaccinated fish. Fish were exposed, under natural conditions, to Flavobacterium columnare, a ubiquitous bacterium associated with columnaris disease. During every time interval, the probability that a vaccinated fish would survive past time, t, was greater than for sham-vaccinated fish and survivor functions were significantly different (p-value <0.001). Overall, vaccinated fish had a 43% lower risk of death during the field trial. Overall incidence was 1.7 times greater for the sham-vaccinated (1.4%/d) as compared to the vaccinated fish (0.8%/d). Vaccination with AQUAVAC-COL (Intervet/Schering-Plough Animal Health) significantly reduced the risk of death from columnaris disease in feed-trained largemouth bass fry.

Topics: Animals; Bacterial Vaccines; Bass; Fish Diseases; Flavobacteriaceae Infections; Flavobacterium; Survival Analysis

The ability of two commercial rapid identification systems, API 20E and BBL Crystal E/NF, to reliably identify bacterial isolates from the internal organs of reared sea bass were compared. The tests gave different results: API 20E identified bacteria as Pseudomonas spp. with 37% accuracy, while BBL Crystal E/NF identified them as Flavobacterium odoratum with 99% accuracy. Although F. odoratum is not a marine fish pathogen, conventional tests conducted with the same isolates were more indicative of them being Flavobacterium spp. than Pseudomonas spp., suggesting that BBL Crystal E/NF was more reliable in this identification. Both systems were found to be applicable for diagnostics of marine fish pathogens, but should be used with caution because of possible misinterpretation.

Topics: Animals; Aquaculture; Bacterial Typing Techniques; Bass; Diagnosis, Differential; DNA, Bacterial; Fish Diseases; Flavobacteriaceae Infections; Flavobacterium; Pseudomonas; Pseudomonas Infections; Sensitivity and Specificity