Effects of Formalin and Chloramine-T Treatments on Oxygen Consumption of Juvenile Salmonids

Abstract

The effects of formalin and chloramine-T on oxygen consumption of juvenile brook trout Salvelinus fontinalis at low water temperature were studied with a flow-through respirometer. No changes were found in the oxygen consumption of these fish after exposure to formalin at 200 and 400 μL/L or to chloramine-T at 10 μL/L during 1-h flow-through treatments. Additionally, there was no evidence of chemical oxygen demand exerted by formalin at dose levels up to 1,600 μL/L or by chloramine-T at I0 μL/L. When juvenile rainbow trout Oncorhynchus mykiss were treated with formalin at 200 μL/L for 1 h in an aerated tank simulating a static bath treatment, sham-treated control tanks had a significantly greater maximum decline in dissolved oxygen than formal in-treated tanks. These studies suggest that posttreatment mortalities that occur after low-temperature bath treatments with these chemicals are not directly related to oxygen consumption.     

Branchial Ionic Flux Responses in Rainbow Trout to Chloramine-T after Acclimation to Different Levels of Water Hardness

Abstract

Whole-body unidirectional and net Na⁺ and Cl^– fluxes were determined in rainbow trout Oncorhynchus mykiss exposed to chloramine-T (9 mg/L) alone or in combination with 17 mmol NaCl/L (0.1 % weight per volume, w/v) after acclimation to either city of Ottawa tap water (TW: Na⁺ 0.121 ± 0.004 mmol/L; K⁺ 0.015 ± <0.001 mmol/L; Ca²⁺ 0.351 ± 0.004 mmol/L; Cl^– 0.141 ± 0.002 mmol/L) or artificial soft water (ASW: Na⁺ 0.043 ± 0.003 mmol/L; K⁺ 0.005 ± <0.001 mmol/L; Ca²⁺ 0.063 ± 0.002 mmol/L; Cl^– 0.026 ± 0.002 mmol/L). Preexposure fluxes revealed that ASW-acclimated fish had reduced rates of Na⁺ uptake and efflux compared with TW-acclimated fish. However, rates of Cl^– uptake among ASW-acclimated fish were comparable with those of TW-acclimated fish. Exposure to chloramine-T in TW resulted in significant increases in the Cl^– efflux, giving rise to a significant and negative net flux. Exposure of ASW-acclimated fish to chloramine-T caused a significant negative increase in the Na⁺ efflux and net flux but only a negative increase in the Cl^– net flux. The addition of 17 mmol NaCl/L (0.1% w/v) eliminated the negative net ionic fluxes, resulting in significant increases in influx. The combined use of chloramine-T with NaCl is a potential method of remediating ionic disturbances that may be caused by treating trout with chloramine-T.     

Effects of a Prophylactic Chloramine-T Treatment on Growth Performance and Condition Indices of Rainbow Trout

Abstract

Chloramine-T has been commonly used as a therapeutic agent for the treatment of bacterial gill disease and related phenomena in the salmonid aquaculture industry, and it is now commonly used as a prophylactic agent to prevent diseases in commercial salmonid hatcheries. Rainbow trout Oncorhynchus mykiss (average weight 98 g) were exposed to chloramine-T at 10 mg/L for 1 h twice weekly (a commonly used regime in the aquaculture industry) for 11 weeks. Fish were fed ad libitum without feed wastage throughout the 11 -week trial. Body weight, specific growth rate, feed conversion index, and appetite were assessed at the end of weeks 3, 6, 9, and 11. Chloramine-T treatment was not associated with either clinical disease or mortality. However, by the end of the trial, growth (based on body weight) of treated fish was significantly suppressed (δ = 7.3%) compared with control fish. Growth suppression was attributed to a significant reduction (δ = 9.3%) of feed conversion efficiency in treated fish. Based on specific growth rates, chloramine-T had an early negative effect on growth. The effect was diminished in later weeks (although not completely lost), which suggests some degree of compensation by the fish to the chemical agent.     

Amyloodiniosis in Cultured Hybrid Striped Bass (Morone saxatilis × M. chrysops) in North Carolina

Abstract

An outbreak of amyloodiniosis in pondcultured hybrid striped bass × white bass (female Morone saxatilis × male M. chrysops) is the northernmost documented outbreak caused by an endemic source in fish of the western Atlantic. Dinospores produced by this isolate of Amyloodinium ocellatum were anteroposteriorly flattened, as contrasted with the gymnodinoid dinospores of the A. ocellatum-type species, suggesting that more than one strain or species of A. ocellatum may exist.     

An outbreak of caseous lymphadenitis in dairy goats: First report of the disease in the Netherlands

Summary

An outbreak of caseous lymphadenitis in which three herds of goats were involved is described. Corynebacterium pseudotuberculosis was shown to be the causative organism. The outbreak was associated with imported goats. As this first report of C. pseudotuberculosis causing caseous lymphadenitis as a clinical entity in small ruminants in the Netherlands, clinical and epizootiological aspects as well as possible methods of control are discussed.     

Reduction of bacterial infections in newly hatched chicks by the use of antimicrobial dips: Preliminary approaches

Summary

Bacteriological examination of hatchery waste eggs, identification of the isolated bacteria, and susceptibility testing against seven antimicrobial agents were used in an attempt to establish a rational basis for reducing bacterial infections in newly hatched chicks.

Chloramphenicol at 1000 ppm was selected as the antibiotic for preliminary dipping trials and 0.45% iodophore (Wescodyne) was added for later trials. The control treatment consisted of formaldehyde fumigation. The following conclusions can be drawn:

(1) Hatchery waste eggs are highly contaminated (69.1%) and enterobacteriaceae predominate (26.6%).

(2) Chloramphenicol is the most effective antimicrobial tested.

(3) Dip treatments with either chloramphenicol alone or chloramphenicol plus Wescodyne result in a reduced percentage of abnormal navels (8.4% and 10.4%), as compared with 21.9% for the control treatment.

(4) Hatchability of either group of dipped eggs is reduced in comparison with fumigated eggs.

(5) Dip treatment with chloramphenicol plus Wescodyne significantly reduces the anal carrier rates for Escherichia coli, Pseudomonas aeruginosa, Salmonella spp., and Staphylococcus aureus. This treatment reduces the incidence of bacterial infection in abnormal navels to zero.     

Observations on the Occurrence of Bacterial Gill Disease and Amoeba Gill Infestation in Rainbow Trout Cultured in a Water Recirculation System

Abstract

Spontaneous outbreaks of bacterial gill disease (BGD) occurred in 17-44-g rainbow trout Oncorhynchus mykiss after they were placed in a water recirculation system. In each of five groups stocked from September 1991 through July 1992, BGD occurred within 6–8 d after stocking. In each instance, BGD was followed by a secondary amoeba infestation. The spontaneous BGD outbreaks did not occur among previously stocked groups that had recovered from earlier BGD disease outbreaks. Examination of gill tissue by Gram stain and indirect fluorescent antibody technique showed increased numbers of filamentous bacteria associated with BGD after the rainbow trout were stocked into the system. Bacterial numbers decreased after a 1-h treatment with chloramine-T at concentrations of 9–15 mg/L but increased within 2 d after treatment. Although the chloramine-T treatments controlled mortality related to BGD, the amoeba infestation persisted. Histological examination of gills showed some focal hyperplasia before the rainbow trout were placed into the recirculation system, but hyperplasia became more extensive and lamellar fusion and mild telangiectasis developed within a week after placement in the system. The density at which the fingerling rainbow trout were stocked and the suspended solids present in tank water may have contributed to the BGD outbreaks. Exposure of juvenile rainbow trout to tank water from the recirculation system before they were placed into the system did not afford them protection against BGD after stocking.     

Journal of Aquatic Animal Health: Guide for Authors 2014

Abstract

Brook trout Salvelinus fontinalis were treated with single 60-min static baths of 250 mg formalin/L, 3% NaCl, and 15 mg Chloramine-T/L to evaluate the efficacy of these compounds against external infections of Aeromonas salmonicida. Prevalence of A. salmonicida was significantly lower in brook trout treated with Chloramine-T than among those treated with formalin or salt. Further laboratory tests substantiated the therapeutic value of a single treatment of ChloramineT (15 mg/L) against A. salmonicida. In two experiments, viable counts of A. salmonicida in mucus did not vary among replicate groups of treated brook trout, but the counts for treated fish were significantly (P < 0.05) lower than those for untreated controls. In vitro tube dilution assays indicated that mean minimum inhibitory concentrations of Chloramine-T for 10 isolates of A. salmonicida were 9.0 mg/L for 1 h and 2.25 mg/L, for 24 h. In field trials at the White River National Fish Hatchery (Bethel, Vermont), the pathogen was detected principally as an external infection of juvenile Atlantic salmon Salmo solar maintained in two culture ponds. In one pond, the bacterium accounted for 100% of the total distribution of tnicroflora isolated from mucus. Seven days after treatment with Chloramine-T, A. sahnonicida accounted for 11% of the total bacterial counts identified from these fish. In the second pond, A. salmonicida composed 3% of the counts of bacteria isolated from the mucus of fish before treatment but was not isolated after treatment.     

Protection of Chinook Salmon Smolts with Oral Doses of Erythromycin against Acute Challenges of Renibacterium salmoninarum

Abstract

We challenged duplicate groups of yearling smolts of chinook salmon Oncorhynchus tshawytscha held in seawater with an intraperitoneal inoculation of the kidney disease bacterium Renibacterium salmoninarum 1 d before and at intervals of 1, 11, and 29 d after a 21-d oral administration of erythromycin thiocyanate at 0.1 g/kg body weight per day. Most mortality attributable to bacterial kidney disease (BKD) in fish challenged with R. salmoninarum but not administered erythromycin occurred 2–3 weeks after challenge; the average survival 35 d after challenge was only 9%. Nearly 70% of the fish challenged 1 d before the erythromycin feeding were alive 35 d after the 21-d treatment, and more than 98% of the fish challenged the day after the 21-d erythromycin treatment survived a further 35 d. Fish challenged 29 d after the erythromycin treatment were not significantly protected against BKD. Chinook salmon that were not challenged with the bacterium but were injected with sterile phosphate-buffered saline and then fed a ration with erythromycin survived at a significantly higher rate than unchallenged fish injected with saline but not fed erythromycin. Fish that were not injected with saline or R. salmoninarum survived at a significantly higher rate than fish handled and injected with saline or pathogen. Because erythromycin protected fish challenged just before and immediately after treatment, the antibiotic should be useful early in an outbreak of BKD and as a prophylactic when stresses are expected.     

Case Report: Outbreak of Bumper Car Disease Caused by Anophryoides haemophila in a Lobster Holding Facility in Nova Scotia,Canada

Abstract

This case report provides pathologic and confirmatory molecular characterization of an outbreak of bumper car disease caused by the scuticociliate Anophryoides haemophila in American lobster Homarus americanus, from a commercial holding facility in Nova Scotia, Canada. Although sporadically and anecdotally reported to be present in Atlantic Canada, this is the first report detailing observations from a natural outbreak of bumper car disease by gross and microscopic pathology and its positive identification by small subunit rRNA gene sequencing. Randomly amplified polymorphic DNA analysis confirmed that the genotype of the present outbreak isolate is identical to the original isolate of A. haemophila reported from Maine lobsters in 1993.     

Randomized field trial comparing the efficacy of florfenicol and oxytetracycline in a natural outbreak of calf pneumonia using lung reaeration as a cure criterion

BackgroundRespiratory infections are the main indication for antimicrobial use in calves. Optimal treatment duration currently is unknown, but shorter duration would likely decrease selection for antimicrobial resistance.Hypothesis/ObjectivesDetermine differences in cure rate and healing time between animals treated with florfenicol and oxytetracycline in a natural outbreak of respiratory disease using reaeration observed on thoracic ultrasound examination as healing criterion.AnimalsCommercial farm housing 130, 3 to 9 month old Belgian blue beef calves.MethodsRandomized clinical trial during an outbreak of respiratory disease. Metaphylactic treatment was initiated, randomly treating animals with either florfenicol or oxytetracycline. Ultrasonographic follow‐up was done the first day and every other day for a 14‐day period. At the individual animal level, treatment was discontinued when reaeration of the lungs occurred. Differences in cure rate and healing time were determined.ResultsOf the 130 animals studied, 67.7% developed a lung consolidation ≥0.5 cm. The mean ultrasonographic healing time was 2.5 days in the florfenicol group compared to 3.1 days in the oxytetracycline group (P = .04). After single treatment, 80.6% and 60.3% had no consolidations in the florfenicol and oxytetracycline groups, respectively (P = .01). A Mycoplasma bovis strain was genetically and phenotypically determined to be susceptible to both antimicrobials.Conclusions and Clinical ImportanceUltrasonographic lung reaeration shows potential as a cure criterion to rationalize antimicrobial use for outbreaks of pneumonia. In our study, florfenicol resulted in a faster cure and higher reduction in antimicrobial usage than did oxytetracycline.     

Novel findings from a beta coronavirus outbreak on an American Miniature Horse breeding farm in upstate New York

This case report describes an outbreak and novel findings associated with a beta coronavirus (BCoV) infection that occurred on an American Miniature Horse (AMH) breeding farm in upstate New York, in January and February of 2013. Twenty-nine AMH and one donkey were present on the farm when the outbreak occurred. One 10-year-old Quarter Horse mare, stabled at a separate location and owned by an employee of the farm, also tested positive. A polymerase chain reaction (PCR) assay for the detection of BCoV was performed at the Animal Health Diagnostic Center (AHDC) at Cornell on all faecal samples. The PCR assay used detects multiple beta coronaviruses, including, but not limited to, equine enteric coronavirus (ECoV). Novel findings regarding this BCoV infection in horses were recognised in this outbreak study. To the authors’ knowledge, this is the largest outbreak of BCoV described thus far in a closed herd on a single premise. The case fatality rate was 0% unlike that described in a previous outbreak of ECoV involving miniature horses and a miniature donkey (Fielding et al. 2015). The morbidity rate was lower in this outbreak than in previously described studies (Oue et al. 2013; Pusterla et al. 2013). This outbreak also demonstrated the potential for BCoV transmission via farm personnel. The duration of shedding of virus in the faeces among some asymptomatic horses in this outbreak was longer than previously described clinical cases of ECoV (Pusterla et al. 2013; Nemoto et al. 2014). This study suggests that asymptomatic animals may play a role in the maintenance of BCoV during an outbreak; therefore, the need for diagnostic testing of both clinically affected and apparently clinically normal horses on a premises followed by appropriate biosecurity and control measures.     

Efficacy of Hydrogen Peroxide to Control Parasitic Infestations on Hatchery-Reared Fish

Abstract

The efficacy of hydrogen peroxide to control external parasitic infestations on juvenile (10–33-g) rainbow trout Oncorhynchus mykiss was evaluated in three clinical field trials. Fish were exposed to hydrogen peroxide concentrations ranging from 0 to 560 mg/L for 30 min once every other day for a total of three treatments. Pre- and posttreatment skin scrapes and gill wet mounts of test fish were microscopically examined to identify and enumerate external parasites. Infestation severity was classified as nonexistent (0 organisms), low (1–10 organisms), moderate (11–20 organisms), or high (?21 organisms). In trial 1, pretreatment skin examinations revealed a severe infestation of the protozoan Ambiphrya on all fish examined. Posttreatment skin examinations conducted within 24 h of the last treatment indicated that all hydrogen peroxide treatments eliminated Ambiphrya, whereas control fish remained severely infested with the protozoan. In trial 2, pretreatment examinations of skin and gill samples indicated a high infestation of the trematode Gyrodactylus (skin) and the protozoan Trichodina (gills) on all fish. Posttreatment examinations conducted within 24 h of the last treatment indicated that Gyrodactylus was eliminated from the skin of all treated fish; however, the high infestation of Trichodina remained on the gills of the test fish. All control fish had high infestation levels of both parasites. A high infestation of Ambiphrya was found on the skin of test fish before treatment (trial 3). Posttreatment examinations conducted 14 d after the last treatment revealed that 56% of the fish were parasite free, whereas the remaining test fish had low infestation levels. Control fish remained severely infested with the parasite. Based on the efficacy data, all hydrogen peroxide treatment regimens were efficacious in the control of Ambiphrya and Gyrodactylus.     

Ovotestis in a Japanese Medaka

Abstract

We observed ovotestis in Japanese medaka Oryzias latipes used to study the effects of bromodichloromethane (BDCM) on gonadal differentiation. Bromodichloromethane, a trihalomethane, is a drinking water disinfection byproduct. Seven-day-old Japanese medaka (n = 30 fish per treatment) were exposed for 10 d to nominal concentrations of BDCM (10 or 25 mg/L) in dimethyl sulfoxide, a carrier solvent control, or a springwater control, then transferred to springwater and reared for 6 months. Ovotestis was present in one female of the 13 Japanese medaka that survived for 6 months after exposure to 10 mg/L BDCM. This is the first report of an intersex condition in a BDCM exposure study. There are no known reports of spontaneous occurrences of ovotestis in Japanese medaka; however, we cannot eliminate the possibility that this single case was spontaneous rather than induced by BDCM. Therefore, further studies with a wide range of concentrations of BDCM are needed to confirm the ovotestis induction potential of BDCM.     

The Effect of High Total Ammonia Concentration on the Survival of Channel Catfish Experimentally Infected with Flavobacterium columnare

Abstract

Ammonia concentrations in water can affect the severity of Flavobacterium columnare infections in fish. Two trials lasting 7 d each were conducted to determine the effect of a single immersion flush treatment of total ammonia nitrogen (TAN; 15 mg/L) on the survival of channel catfish Ictalurus punctatus infected with F. columnare; the chemical was added while the water flowed continuously through the tanks. Both trials consisted of four treatments: (1) no ammonia exposure and no bacterial challenge (control), (2) ammonia exposure only, (3) bacterial challenge only, and (4) both ammonia exposure and bacterial challenge. Two hours after exposure to ammonia, the highest un-ionized ammonia level was 0.43 mg/L. The percent un-ionized ammonia is based on TAN, temperature, and pH. Caudal fins from three fish in each treatment were sampled at 24 h posttreatment to be analyzed by quantitative real-time polymerase chain reaction (qPCR). No significant difference in survival (mean ± SE) was noted between the channel catfish in treatment 1 (95.2 ± 1.2%) and those in treatment 2 (95.6 ± 1.0%); however, survival in both treatments 1 and 2 differed significantly from that in treatments 3 (8.5 ± 4.5%) and 4 (41.8 ± 12.7%). Treatment 4 catfish had significantly higher survival than treatment 3 catfish. Quantitative PCR data showed that treatment 4 fish had significantly less F. columnare (7.6 × 10⁵) than did treatment 3 fish (1.2 × 10⁷), and treatment 2 fish (8.5 × 10³) had significantly less bacteria than did treatment 1 fish (6.9 × 10⁴), indicating that ammonia limited the F. columnare infection. The highest mean concentration of the bacteria (3.9 × 10⁷) was found on moribund fish. The ammonia concentrations tested did not negatively influence fish survival but interfered with the infection process. An in vitro assay was also conducted to evaluate the direct effects of ammonia on F. columnare.

Received September 15, 2010; accepted May 7, 2011     

Lessons learned from a strangles outbreak on a large Standardbred farm

Streptococcus equi subspecies (ssp.) equi infection (strangles) remains one of the most frequently diagnosed and costly infectious diseases of horses. Large breeding herds, where a disease outbreak competes for personnel and financial resources needed for foaling management, present a special challenge for equine practitioners. A 15‐month outbreak involving 62 clinical cases of strangles occurred on a large Standardbred breeding farm (average population of 1400 horses). Sixteen asymptomatic horses were found to be PCR (polymerase chain reaction)‐positive for S. equi ssp. equi. During the outbreak, serological samples from 48 clinically normal horses were found to be seropositive for S. equi ssp. equi, confirming herd‐wide exposure. After several clinical cases of strangles had been diagnosed, an intranasal S. equi ssp. equi vaccine was administered to clinically normal horses (n = 558) considered to be at risk of exposure. Strangles complications included 7 fatalities (none in vaccinated horses) and 6 cases of purpura haemorrhagica (4 in vaccinated horses). Midway through the outbreak, injectable, sustained release ceftiofur crystalline free acid (CCFA), given as an initial dose followed by a second dose 4 days later, was used exclusively for systemic antimicrobial treatment of clinically affected and PCR‐positive horses. This antimicrobial regimen coincided with a reduction in disease incidence and eventual resolution of the outbreak. Two horses with persistent guttural pouch infection were endoscopically confirmed as carrier horses. The herd history demonstrated that a strangles outbreak will often result in asymptomatic carrier horses and that identification and treatment of these horses are necessary to eliminate long‐term sources of infection. Ceftiofur crystalline free acid was found to be a suitable antimicrobial due to its activity against S. equi ssp. equi and the efficiencies associated with twice parenteral dosing during a 10‐day treatment period. Occurrence of purpura in 4 vaccinated horses suggests that vaccination should be reserved for healthy seronegative horses and avoided during an active outbreak.     

The behaviour pattern of lambs after castration using a rubber ring and/ or castrating clamp with or without local anaesthetic

Aims. To determine if individual behaviours may be used to compare the distress caused by the different methods of castration.

Methods. A controlled experiment in which the behaviour pattern of 174 lambs given one of twenty treatments (six ring, five clamp plus ring and four clamp castration with a variety of local anaesthetic placements plus five control treatments) were monitored for 4 hours from about 5 seconds after treatment.

Results. The contrast between the behaviour patterns of lambs castrated by different methods with or without local anaesthesia and control groups allowed the identification of individual behaviours stimulated by the different methods of castration. After ring castration there was an increase in restlessness, in contrast to clamp castration, which had no obvious individual behaviour associated with it during the 4 hours after treatment. Clamp plus ring castration resulted in a behaviour pattern similar to those caused by ring castration alone.

Conclusions. Individual behaviours can only be used to compare the distress caused by different methods of castration if the methods stimulate similar behaviours. The distress which occurs after ring or clamp castration cannot be compared using behavioural observations because the two techniques stimulate different types of behaviour.     

Decreased Resistance to Edwardsiella ictaluri Infection in Channel Catfish Intraperitoneally Administered an Oil Adjuvant

Abstract

The effects of intraperitoneal injection of squalene, an oil adjuvant, on nonspecific mortality of channel catfish Ictalurus punctatus and on their resistance to experimental Edwardsiella ictaluri infection were studied. Yearling channel catfish were assigned to control (N = 22) or squalene (N = 25) treatment groups, and mortality was monitored for 14 d following treatment. On day 14 both groups were infected with E. ictaluri, the causative agent of enteric septicemia of catfish, and mortality was monitored for an additional 11 d. Before infection, mortality did not differ between groups. After E. ictaluri infection, fish that received squalene were at a substantially higher risk of dying than control fish (relative risk after squalene treatment = 6.86). These results suggest that intraperitoneal administration of squalene, although not directly toxic, decreased resistance to E. ictaluri infection.