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Results for “Journal of Aquatic Animal Health”

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At least 73 records · Page 4Linked to original sources
USGS1990

Multiplication of infectious hematopoietic necrosis virus in rainbow trout following immersion infection: whole-body assay and immunohistochemistry

The sites of replication of infectious hematopoietic necrosis virus (IHNV) in infected tissues were detected in fingerling rainbow trout Oncorhynchus mykiss by in situ histologic techniques following immersion infection. Virus antigens in tissues were detected by a neutralizing mouse monoclonal antibody and a one-step anti-mouse biotin-streptavidin conjugated to horseradish peroxidase. The efficiency of infection and virulence of the virus determined by mortality rates showed high virulence of the selected IHNV isolates, and viral replication in individual fish showed that virus content of the fish increased rapidly from the second day to the seventh day postinfection. The earliest viral lesions following infection were detected in the epidermis of the pectoral fins, opercula, and ventral surface of the body. Virus lesions became evident in kidneys on the third day. By the fifth day, when there was a significant increase in virus titer, foci of viral replication were detected in gill tissue and in the anterior internal tissues below the epidermis. Subsequently, extensive virus replication and tissue destruction were observed in the spleen, dorsal adipose tissues, ventricle, and pseudobranch. Replication in the liver, the muscularis layers of the digestive tract, and the general body musculature followed later. These infection experiments indicated that the epidermis and gills of fish constitute important sites of early IHNV replication.

Journal of Aquatic Animal Health↗
USGS1990

Changes in numbers of leukocytes in immune organs of juvenile coho salmon after acute stress or cortisol treatment

We examined the effects of acute stress and cortisol treatment on the number of leukocytes (normalized for fish body weight) in the blood, thymus, spleen, and anterior kidney of juvenile coho salmon Oncorhynchus kisutch . In acutely stressed or cortisol-fed fish, the numbers of leukocytes increased significantly in the thymus and anterior kidney, and decreased significantly in blood and spleen within 1 d after treatment. Numbers of cells in the anterior kidney, blood, and spleen returned to control levels by 3 d after treatment, but cell numbers in the thymus remained significantly greater than control values until 3–7 d after acute stress. Although dietary cortisol resulted in increased plasma cortisol titers and caused the same changes in leukocyte distribution as those caused by acute stress, the magnitude or duration of elevated cortisol levels and leukocyte numbers were not correlated. These results suggest that, although increased plasma cortisol titers induced by stress may be involved in the change in number of cells in various immune organs, factors other than cortisol are involved as well.

Journal of Aquatic Animal Health↗
USGS1991

Hatchery efficacy trials with chloramine-T for control of bacterial kidney disease

Three hatchery trials were carried out to determine the efficacy of chloramine-T for the control of bacterial gill disease in rainbow trout Oncorhynchus mykiss , ranging in weight from 2.5 to 54 g. In each trial, we used a single flow-through treatment of 8.5 mg chloramine-T/L. The single treatment provided effective control in all three trials; however, results were best when treatment was begun in the early stages of an outbreak. A second or third treatment may be required if an outbreak is in an advanced stage or if fish are under stress.

Journal of Aquatic Animal Health↗
USGS1991

Infectious hematopoietic necrosis (IHN) and viral hemorrhagic septicemia (VHS): Detection of the trout antibodies to the causative viruses by means of plaque neutralization, immunofluorescence, and enzyme-linked immunosorbent assay

Sera collected from cultured rainbow trout Oncorhynchus mykiss surviving outbreaks of infectious hematopoietic necrosis (IHN) or viral hemorrhagic septicemia (VHS) were examined for the presence of antibodies to both of the causative viruses, infectious hematopoietic necrosis virus (IHNV) and Egtved virus (viral hemorrhagic septicemia virus: VHSV). Sera were screened with three serological tests: 50% plaque neutralization test (PNT), immunofluorescence (IF), and enzyme-linked immunosorbent assay (ELISA). In sera from 20 rainbow trout surviving IHN, antibodies to IHNV were detected in 9 fish by PNT, in 12 fish by IF, and in 9 fish by ELISA. In these sera, antibodies cross-reacting with VHSV were rare (detected in 0 fish by PNT, in 1 by IF, and in 1 by ELISA). In sera from 20 rainbow trout surviving VHS, antibodies to VHSV were detected in 9 fish by PNT, in 16 fish by IF, and in 18 fish by ELISA. A considerable percentage of the VHS-survivor sera contained antibodies that cross-reacted with IHNV, as detected by ELISA (16 fish) and 1F (7 fish) but not by PNT (0 fish). The three serological tests appear to be useful tools for IHNV and VHSV epidemiology; however, the presence of cross-reacting antibodies in some sera suggests caution when farms require specific pathogen-free certification for one of the viruses in the presence of the other.

Journal of Aquatic Animal Health↗
USGS1991

Resistance of underyearling and yearling Atlantic salmon and lake trout to supersaturation with air

Juvenile Atlantic salmon Salmo salar and lake trout Salvelinus namaycush of different sizes were exposed for 96 h to water supersaturated with air. Underyearlings (Atlantic salmon shorter than 66 ± 8 mm [mean total length ± SD] and lake trout shorter than 96 mm) were resistant to high dissolved-gas pressures. The level of supersaturation causing 50% mortality was lower for yearling Atlantic salmon (148 ± 17 mm long) than for underyearling Atlantic salmon, and sensitivity to supersaturation was greater in lake trout 96 ± 1 to 153 ± 17 mm long than in those 23 ± 1 to 46 ± 4 mm long. Incidence of cutaneous emphysema and other signs of gas bubble disease increased as supersaturation increased. The number of bubbles and number of sites with bubbles were higher in the older fish. Among fish 150 ± 17 mm long, Atlantic salmon seemed to be less resistant to gas supersaturation than did lake trout.

Journal of Aquatic Animal Health↗
USGS1991

Demonstration of the salmonid humoral response to Renibacterium salmoninarum using a monoclonal antibody against salmonid immunoglobulin

The specificity of the antibody response of salmonids to Renibacterium salmoninarum antigens was demonstrated by western blotting techniques that utilized a monoclonal antibody against salmonid immunoglobulin. In this study, the specificity of the response in immunized chinook salmon Oncorhynchus tshawytscha was compared with the response in naturally infected chinook salmon and coho salmon O. kisutch , and immunized rabbits. The antibody response in immunized salmon and rabbits and the naturally infected fish was primarily against the 57–58kilodalton protein complex. In addition to recognizing these proteins in the extracellular fraction and whole-cell preparations, antibody from the immunized salmon and rabbits detected four proteins with lower molecular masses. Western blotting techniques allow identification of the specific antigens recognized and are a useful tool for comparing the immunogenicity of different R. salmoninarum preparations. Immunofluorescent techniques with whole bacteria were less sensitive than western blotting in detecting salmonid anti- R. salmoninarum antibody.

Journal of Aquatic Animal Health↗
USGS1992

Experimentally induced whirling disease II; Determination of longevity of the infective Triactinomyxon stage of Myxobolus cerebralis by vital staining

Effects of temperature and aging on viability and infectivity of laboratory-produced actinosporean triactinomyxon spores (infective stage of the organism causing whirling disease) were studied. In vitro staining of triactinomyxon spores with vital fluorescein diacetate correlated with the ability of the spores to infect fry of rainbow trout Oncorhynchus mykiss . The experimentally produced actinosporean stage of Myxobolus cerebralis was short-lived, persisting for only 3–4 d at 12.5°C and for less time at warmer temperatures. The vital staining method has potential for screening therapeutants intended to control myxosporean infection of fish.

Journal of Aquatic Animal Health↗
USGS1992

Physiological and hematological changes in Chum Salmon artificially infected with Erythrocytic Necrosis virus

Chum salmon Oncorhynchus keta were injected with erythrocytic necrosis virus (ENV) to study the physiological and hematological consequences of ENV infection. Infected and control fish were held in pathogen-free seawater and sampled for 5 weeks. Physiological tests included measures of plasma cortisol, glucose, protein, and osmolality; blood lactic acid; and liver glycogen. In general, ENV-infected fish had lower plasma glucose and blood lactic acid, and higher liver glycogen concentrations than did control fish. Hematological tests included red and white blood cell (RBC and WBC) counts, hematocrit, measurement of blood hemoglobin concentration, and a determination of erythrocyte fragility. Infected fish had lower RBC counts, hematocrits, and hemoglobin concentrations; higher WBC counts; and less fragile erythrocytes than did control fish. The hematology data indicated that erythrocytes of infected fish had higher mean corpuscular volume, depressed mean corpuscular hemoglobin concentration, and slightly lower mean corpuscular hemoglobin. Erythrocytic inclusions were observed in the cytoplasm of RBCs from infected fish. The infection progressed steadily through week 4, after which the fish appeared to begin recovering. In a second study, fish were infected with ENV for 3 weeks, and recovery from a stress challenge test was measured. Plasma glucose concentrations and osmclality were higher in infected fish, whereas plasma cortisol and blood lactate were only slightly elevated. These studies indicate that chum salmon withstood the effects of ENV infection without in-eversible physiological consequences. However, when subjected to a stress challenge test, infected fish recovered more slowly than control fish and had increased osmoregulatory difficulties.

Journal of Aquatic Animal Health↗
USGS1992

Prevalence of Renibacterium salmoninarum among downstream-migrating salmonids in the Columbia River

Bacterial kidney disease (BKD) is an important contributor to mortality of salmonids in hatcheries in the Columbia River basin. However, the impact of BKD on the survival of downstream migrants is difficult to determine because there is little information on the disease-related mortality among these fish. In this study, the impact of BKD on juvenile salmonids was examined by determining the percentage of downriver migrants infected with Renibacterium salmoninarum (the causative agent of BKD) and evaluating the effects of salt water on the progress of the disease. During the 2 years of this study, approximately 20% of the three species of migrating hatchery and wild salmonids ( Oncorhynchus spp.) collected were infected with R. salmoninarum . Mortality caused by BKD increased when fish were held in salt water.

Journal of Aquatic Animal Health↗
USGS1992

Detection of Aeromonas salmonicida the mucus of salmonid fishes

Mucus of salmonids was evaluated as a source for nonlethal detection of the pathogen Aeromonas salmonicida in fish. The bacterium was readily isolated from mucus on dilution plates when Coomassie Brilliant Blue agar was the primary plating medium. Kidney samples from the fish that served as sources of mucus were similarly processed. Infection was detected in 56% of mucus samples from lake trout Salvelinus namaycush that were undergoing an epizootic of furunculosis, but only 6% of the kidneys from these fish were positive for the pathogen. Only 1% of asymptomatic brown trout Salmo trutta sampled at another fish hatchery had A. salmonicida in their mucus, and none had a kidney infection. Combined results from the examination of two pools of Atlantic salmon Salmo salar reared at a third hatchery indicated that 37% of these fish had mucus infections caused by A. salmonicida , but only 4% of the kidneys were infected.

Journal of Aquatic Animal Health↗
USGS1992

Communications: Blood chemistry of laboratory-reared Golden trout

Golden trout Oncorhynchus aguabonita obtained from a wild stock as fertilized eggs were reared in the laboratory for 21 months. The laboratory-reared golden trout in our study reached sexual maturity earlier and grew more rapidly than wild golden trout do (according to the scientific literature). Male fish averaged 35.6 cm in total length and 426 g in weight, and females averaged 36.2 cm and 487 g. All golden trout were sexually mature when used for hematological analysis. The hematological profile (hematocrit, red blood cells, white blood cells, and thrombocytes) of golden trout was similar to that reported elsewhere for other trout species. Male and female golden trout did not have significantly different thrombocyte counts; however, the immobilization treatment used on the fish (anesthesia versus a blow to the head) resulted in significant treatment differences in thrombocyte numbers and interaction effect of sex in treatment for hematocrits. Gravid female golden trout had significantly higher plasma protein and calcium levels than did males. The ionic compositions of plasma (sodium, potassium, calcium, magnesium, copper, zinc, iron, and chloride) and gallbladder bile (calcium and chloride) were similar to those reported for other salmonids.

Journal of Aquatic Animal Health↗
USGS1992

In vitro infection of salmonid epidermal tissues by infectious hematopoietic necrosis virus and viral hemorrhagic septicemia virus

The ability of two rhabdoviruses, infectious hematopoietic necrosis virus (IHNV) and viral hemorrhagic septicemia virus (VHSV), to infect fish skin was investigated by in vitro infection of excised tissues. Virus replication was determined by plaque assay of homogenized tissue extracts, and the virus antigen was detected by immunohistology of tissue sections. Gill, fin, and ventral abdominal skin tissues of rainbow trout Oncorhynchus mykiss that had been infected in vitro with a virulent strain of IHNV (193–110) produced substantial increases in virus titer within 24 h. Titers continued to increase up until day 3 of incubation; by this time, virus had increased 1,000-fold or more. This increase in IHNV titer occurred in epidermal tissues of fingerlings and of older fish. In another experiment, IHNV replicated in excised rainbow trout tissues whether the fish had been subject to prior infection with a virulent strain of IHNV (Western Regional Aquaculture Consortium isolate) or whether the fish had been infected previously with an attenuated strain of the virus (Nan Scott Lake, with 100 passes in culture). A virulent strain of VHSV (23/75) replicated effectively in excised gill tissues and epidermal tissues of rainbow trout and chinook salmon O. tshawytscha ; however, the avirulent North American strain of VHSV (Makah) replicated poorly or not at all.

Journal of Aquatic Animal Health↗
USGS1993

Plasmid-mediated romet resistance of Edwardsiella ictaluri

Romet®, a potentiated sulfa drug composed of five parts sulfadimethoxine and one part ormetoprim, is used to treat channel catfish Ictalurus punctatus infected with Edwardsiella ictaluri , the causal agent of enteric septicemia of catfish (ESC). Recently, several Romet-resistant isolates of E. ictaluri were isolated from channel catfish that had died from ESC in Virginia and Mississippi. This antimicrobial resistance was determined to be plasmid-encoded, as shown by agarose gel electrophoresis of plasmid DNA, and by the fact that the plasmid and associated antimicrobial resistance could be transferred to a recipient by single-step conjugation. Size of the R plasmid was approximately 55 kilobase pairs. Plasmids also conferred resistance to tetracycline, oxytetracycline, streptomycin, trimethoprim, and SXT (another potentiated sulfonamide, composed of trimethoprim and sulfamethoxazole). Each Romet-resistant E. ictaluri isolate was mated with a plasmid recipient, the Romet-sensitive Escherichia coli isolate 1932. Transconjugates were selected by plating on Mueller-Hinton agar that contained antimicrobials, and the mean transfer frequency was 1.483 × 10 −3 transconjugates per donor cell in the mating mixture. Each E. coli transconjugate was then mated with 20 Romet-sensitive isolates of E. ictaluri to assess the propensity of these E. ictaluri isolates to accept the R plasmid. The average transfer frequency when E. ictaluri isolates of channel catfish origin (N = 14) were used as recipients was 1.197 × 10 −2 transconjugates per donor cell in the mating mixture; mean transfer frequency when E. ictaluri isolates not originating from channel catfish were used was 1.019 × 10 -3 transconjugates per donor cell, which was significantly less (P = 0.0002).

Journal of Aquatic Animal Health↗
USGS1993

Comparison of plasmids isolated from Romet-30-resistant Edwardsiella ictaluri and tribrissen-resistant Escherichia coli

Edwardsiella ictaluri , the etiological agent of enteric septicemia of channel catfish (ESC) is the leading cause of bacterial disease in commercially raised channel catfish Ictalurus punctatus . The only drug approved by U.S. Food and Drug Administration for use against ESC is Romet-30. Recently, several isolates were obtained that had a naturally occurring resistance to Romet-30. On further characterization these isolates were shown to possess a 55-kilobase (kb) plasmid that encodes resistance to the drug. We compared Romet-30-resistant E. ictaluri and a Tribrissen-resistant strain of Escherichia coli (strain 1898) isolated from equine cystitis. Antimicrobial profiles, plasmid screening, restriction digest, and Southern blot analysis indicated that the two plasmids are very similar. The resistance afforded to the E. coli was encoded by a 55-kb plasmid. Each of the R plasmids conferred resistance to Romet-30, tetracycline, and Terramycin (oxytetracycline). The R plasmid from E. coli strain 1898 was transferred to Romet-30-sensitive isolates of E. ictaluri by single-step conjugation, rendering the transconjugates resistant to Romet30, tetracycline, and Terramycin. Each plasmid was cleaved into fragments by restriction enzymes, then electrophoresed in an agarose gel and transferred to nitrocellulose. A labeled probe prepared from the R plasmid of E. ictaluri isolate 5-90-156, one of the original Romet-30-resistant E. ictaluri isolates, was added. Restriction enzyme digestion resulted in an equal number of fragments of equal mobility for the two plasmids, and the probe hybridized with the same fragments of each plasmid. These results indicate that the R plasmids of E. ictaluri and E. coli are similar, if not identical.

Journal of Aquatic Animal Health↗
USGS1993

Fin condition of Atlantic salmon reared at high densities in heated water

We assessed the condition of dorsal and pectoral fins of parr of Atlantic salmon Salmo salar that were reared for 70 d at 17.5°C to final densities of 14–55 kg/M 2 (rearing-unit bottom area) or 80–310 kg/m 3 (rearing-unit volume). Pectoral fins were not significantly affected by rearing density, but dorsal fins were more eroded in fish reared at the highest density than in fish checked before the rearing experiments or in those reared at lower densities. Densities as great as 41 kg/m 2 (229 kg/m 3 ) did not affect fin quality of Atlantic salmon reared at 17.5°C.

Journal of Aquatic Animal Health↗
USGS1993

Effects of dietary selenium and vitamin E on red blood cell peroxidation, glutathione peroxidase activity, and macrophage superoxide anion production in channel catfish

Fingerling channel catfish Ictalurus punctatus were fed purified diets either unsupplemented and deficient in both selenium and vitamin E, deficient in either selenium or vitamin E, adequate in both selenium (0.2 mg/kg) and vitamin E (60 mg/kg), or excessive in both nutrients (four times the recommended levels). After 115–120 d of feeding the experimental diets, the red blood cell membranes offish fed diets deficient in vitamin E were more susceptible to peroxidation than were those of fish fed diets that met or exceeded vitamin E recommendations. Hepatic, selenium-dependent glutathione peroxidase activity was suppressed in fish fed diets deficient in selenium when compared with this enzyme activity in fish fed diets containing recommended or higher levels of selenium. Intracellular superoxide anion production of macrophages was higher in fish fed the diet fortified with four times the recommended levels of both nutrients than in fish fed the other diets. None of the results indicated that selenium and vitamin E were complementing each other or that one nutrient was compensating for a deficiency of the other. The results of this study support the presently recommended levels of selenium and vitamin E for channel catfish diets and indicate that higher-than-recommended levels of one or both nutrients may enhance macrophage function.

Journal of Aquatic Animal Health↗
USGS1993

Effect of vitamin E on the immune response of channel catfish to Edwardsiella ictaluri

Three-month-old fingerling channel catfish Ictalurus punctatus were fed purified diets supplemented with ∝-tocopherol acetate to provide 0, 60, and 2,500 mg vitamin E/kg for 180 d. A 30-s immersion bath and an oral booster were used to deliver a bacterin of formalin-killed Edwardsiella ictaluri to half of the fish from each dietary treatment. Resistance of red blood cells to peroxidation was used as an index of antioxidant status. The susceptibility of red blood cells to oxidative hemolysis decreased with increasing levels of dietary vitamin E. Vaccinated and nonvaccinated fish were evaluated for agglutinating antibody titers and macrophage activity. Humoral antibody titers in response to E. ictaluri were significantly (P ≤ 0.05) higher in vaccinated fish than in nonvaccinated fish; however, no such differences in agglutinating antibody titers were detected among any of the dietary treatment groups. Both vaccination and vitamin E significantly enhanced the ability of macrophages to phagocytize virulent E. ictaluri . Results of this study indicate that elevated levels of dietary vitamin E may affect the ability of channel catfish to respond immunologically to bacterial pathogens.

Journal of Aquatic Animal Health↗
USGS1993

Assay to evaluate the reaction kinetics of Chondroitin AC lynase produced by Cytophaga columnaris

The development of an assay to quantitate chondroitin AC lyase activity of Cytophaga columnaris isolates is described. Assay conditions were defined by using C. columnaris originally isolated from channel catfish Ictalurus punctatus , coho salmon Oncorhynchus kisutch , goldfish Carassius auratus , and striped bass Morone saxatilis affected with clinical columnaris disease. Supernatant and cellular components of broth cultures exhibited strong activity, and rates of chondroitin sulfate degradation ranged from 20.0 to 81.4 μg/(mL.h) for the cell component and from 35.4 to 83.4 μg/(mL.h) for the supernatant. Degradation rates were calculated by simple linear regression analysis, and most correlations ranged from −0.90 to −1.00. The assay provided results within 2–3 h, and the enzyme is active under a wide range of pH (5–9) and temperature (10–50°C) conditions. The assay can be used as a simple diagnostic aid to differentiate C. columnaris from Cytophaga psychrophila , but more importantly, as a quantitative tool to explore any relationship between specific chondroitin lyase activity and columnaris disease.

Journal of Aquatic Animal Health↗