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Objective: The antiparasitic effect of peracetic acid (PAA) was evaluated against an infestation of the protozoan Trichodina spp. in naturally infected juvenile domestic seventh‐generation (F7) Striped Bass Morone saxatilis. Methods: Replicated treatments (n = 3) consisted of 1 and 2 mg/L PAA and a control; treatments were applied every other day for three treatments (30‐min static exposure). Infestation intensity was enumerated 20–24 h after each treatment by counting the number of Trichodina present in a wet mount of excised gill tissue. Result: Neither treatment rate was able to completely eradicate the parasite; however, 2 mg/L PAA resulted in a statistically significant reduction, which equated to 75% reduction of observed parasites. Conclusion: The 2‐mg/L PAA treatment regimen in the present study is proposed as a safe, environmentally friendly, and effective method for reducing the intensity of Trichodina infestations in Striped Bass. Impact statementDefining new treatment regimens for common aquaculture parasites is beneficial to the industry. Emphasis on environmentally friendly chemicals is also good for the industry. Improving animal welfare can be achieved by reducing parasites in fish. [ABSTRACT FROM AUTHOR]

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. [ABSTRACT FROM AUTHOR]

Columnaris disease is responsible for substantial losses throughout the production of many freshwater fish species. One of the ways in which the bacterium Flavobacterium columnare is so effective in initiating disease is through the formation of biofilms on fish skin and gills. To further explore the interaction between host factors and bacterial cells, we assayed the ability of vertebrate mucus to enhance F. columnare biofilm development. Different concentrations of catfish, tilapia and pig mucus (5–60 µg/ml) increased biofilm growth at varying degrees among F. columnare isolates. Our data suggest that vertebrate mucus acts as a signalling molecule for the development of F. columnare biofilms; however, there are clear disparities in how individual isolates respond to different mucus fractions to stimulate biofilms. The expression of iron acquisition genes among two genomovar II isolates showed that ferroxidase, TonB receptor and the siderophore synthetase gene were all significantly upregulated among F. columnare biofilms. Interestingly, the siderophore acetyltransferase gene was only shown to be significantly upregulated in one of the genomovar II isolates. This work provides insight into our understanding of the interaction between F. columnare and vertebrate mucus, which likely contributes to the growth of planktonic cells and the transition into biofilms. [ABSTRACT FROM AUTHOR]

Columnaris disease is an important bacterial disease of commercially grown channel catfish, Ictalurus punctatus. Copper sulphate (CuSO4) has been shown to be therapeutic and prophylactic as a water treatment for columnaris disease. Copper is an essential dietary component in animal feeds and CuSO4 is typically included in base diets; a study was conducted to evaluate whether fish feed supplemented with additional CuSO4 at 0, 40 and 80 mg kg−1 of diet and fed at a daily rate of 3% body weight would affect survival to columnaris disease. Results indicate fish fed the copper-supplemented diet for 2 weeks significantly increased survival following F. columnare challenge. This increase appeared to be dose-dependent. The mean per cent survival (±SEM) for fish fed the base diet (unsupplemented) for 2 weeks and then challenged was 2.0% ± 1.1. Fish fed the base plus 40 mg CuSO4 kg−1 had a mean survival of 22.0% ± 11.0. Fish fed the base plus 80 mg CuSO4 kg−1 had a mean survival of 29.3% ± 13.4. The mean per cent survival for fish fed the base diet for 4 weeks and then challenged was 28.3% ± 9.0. Fish fed the base plus 40 mg CuSO4 kg−1 for 4 weeks had a mean survival of 12.5% ± 6.3. Fish fed the base plus 80 mg CuSO4 kg−1 for 4 weeks had a mean survival of 40.5% ± 8.1. There was a significant effect after 4 weeks with fish fed the base plus 80 mg CuSO4 kg−1 mg not with 40 mg kg−1. [ABSTRACT FROM AUTHOR]

Four studies were conducted to compare the effects of copper sulfate (CuSO4), when delivered in either a flow-through or a static system, on the survival of Golden ShinersNotemigonus crysoleucasand Fathead MinnowsPimephales promelasinfected withFlavobacterium columnare. The treatment regimens were administered to fish in well water and were based on the recommended treatment rate (1% of alkalinity). Golden Shiners (experiments 1 and 3) and Fathead Minnows (experiments 2 and 4) were treated separately. In experiments 1 and 2, the treatment rate was 2.0 mg/L CuSO4applied to a flow-through system daily for five consecutive days; control fish were untreated. Study durations were 7 d with the majority of the mortalities occurring in the first 5 d. Survival rates in the flow-through system were 77% and 69% for CuSO4-treated Golden Shiners and Fathead Minnows, respectively. Survival in both species was significantly different from that in their untreated control fish, which was 33% for Golden Shiners and 41% for Fathead Minnows. Static applications of CuSO4were investigated in experiments 3 and 4. Treatment doses were 0, 0.5, 1, 2, and 4 mg/L (approximately 0.0, 0.25, 0.5, 1, and 2 times the recommended rate). Survival of Fathead Minnows in this experiment was 10, 28, 52, 47, and 35% in the 0, 0.5, 1, 2, and 4 mg/L CuSO4treatments, respectively. The corresponding survival of Golden Shiners was 49, 50, 65, 75, and 60% in the 0, 0.5, 1, 2, and 4 mg/L CuSO4treatments, respectively. Received March 28, 2014; accepted August 2, 2014 [ABSTRACT FROM PUBLISHER]

A study was conducted to compare the effects of two chemical therapeutants on channel catfish (CCF)Ictalurus punctatusconcurrently infected withFlavobacterium columnareandIchthyobodo necator. Copper sulfate (CuSO4) and potassium permanganate (KMnO4) were investigated for their ability to reduce the bacterial load, parasite load, and subsequent mortality.Treatment rates of CuSO4or KMnO4were 2.1 mg/L and 3.0 mg/L, respectively, and were applied at 24 h intervals on three consecutive days and control fish were untreated. Fin and gill samples were taken on day 4 (24 h after the final treatment) and day 10 (one week after the final treatment) for quantification of parasite and bacterial load. The survival rate of CuSO4-treated fish (73.0 %) was significantly different from the untreated control fish (41.5%). KMnO4-treated fish was (53.6%) and not significantly different from untreated control or CuSO4-treated fish.I. necatorloads were significantly reduced by both CuSO4and KMnO4,but only CuSO4significantly reduced theF. columnareload. [ABSTRACT FROM PUBLISHER]

I chthyobodo necator is a single-celled biflagellate parasite, which in high density can cause significant mortality in young fish. Copper sulphate ( CuSO4), potassium permanganate ( KMnO4) and peracetic acid ( PAA) were evaluated for effectiveness against ichthyobodosis. Treatments were: untreated control, 2.1 mg L−1CuSO4, 3.0 mg L−1 KMnO4, 1.5 mg L−1 PAA and 3.0 mg L−1 PAA, and were applied to flow-through tanks on three consecutive days. The study was designed to simulate the flow-through systems utilized in the commercial rearing of juvenile channel catfish ( I ctalurus punctatus). Mortality was monitored daily to compare survival rate among treatments. Parasite intensity was assessed pre chemical exposure and 20-24 h after the third application to determine effectiveness of the treatment. An assessment was also done 7 days post application to investigate possible reoccurrence. Copper sulphate, KMnO4 and PAA (3.0 mg L−1) significantly reduced the infestation rate of I . necator. Copper sulphate significantly improved the survival of I . necator infested channel catfish after three flow-through applications compared with the untreated control. The 3.0 mg L−1 PAA resulted in significantly lower survival than the untreated control, the 1.5 mg L−1 PAA and the KMnO4 were not statistically different from the untreated control. [ABSTRACT FROM AUTHOR]

Commercial products containing peracetic acid ( PAA) are strong disinfectants with a wide spectrum of antimicrobial activity and have been suggested as potential therapeutic agents in aquaculture. The aim of this study was to compare the in vitro reduction of growth on two fish pathogens, Flavobacterium columnare and Saprolegnia parasitica, by seven commercial PAA-containing products. Flavobacterium columnare was exposed to 1, 2, 4, 6, 8 and 10 mg L−1 PAA and S. parasitica was exposed to 0.5, 1, 2, 4, 6, 8 and 10 mg L−1 PAA in petri dishes for 24 h incubation. The reduction of growth was measured in comparison to a PAA-free control. A reduction of the growth was observed for both pathogens with increasing PAA concentration. Hydrogen peroxide ( H2O2) possibly has a role in the effectiveness of the products, since products with lower PAA concentrations had a higher concentration of H2O2. The commercial products with a low concentration of PAA and a low PAA: H2O2-ratio were generally more effective against pathogens. The practical application of the products with low PAA concentration should be prioritized. [ABSTRACT FROM AUTHOR]

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.

A simple and reproducible microdilution method was developed to test the susceptibility of the bacterium Flavobacterium columnare to antibiotics in vitro. The testing was conducted at 28 degrees C for 44-48 h at two dilutions of Mueller-Hinton broth (DMHB) using a standardized inoculum, a reference isolate of Escherichia coli ATCC25922 as a quality control organism, positive and negative control wells, and standardized custom-made microtiter plates. The E. coli ATCC25922 and F. columnare ATCC23463 (the species type strain) had significantly better growth in DMHB at 1:5 (4 g/L) than at 1:7 (3 g/L). The E. coli ATCC25922 was found to be acceptable as a reference isolate and produced minimum inhibitory concentration (MIC) values similar to those in the range published by the Clinical and Laboratory Standards Institute derived using standard Mueller-Hinton broth. The new method was used to determine the MIC of 23 F. columnare isolates (representing the three genotypes of the species) to enrofloxacin, ampicillin, oxytetracycline, erythromycin, florfenicol, flumequine, ormetoprim/sulfadimethoxine, and oxolinic acid.