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Myxosoma cerebralis: Isolation and concentration from fish skeletal elements - Sequential enzymatic digestions and purification by differential centrifugation

An effective sequential procedure for recovery of Myxosoma cerebralis spores from infected trout was developed, and quantification of spores was carried out at each step of release and concentration. Methods are described for fresh and frozen material. Effective concentration of from 1100- to 9000-fold and an estimated efficiency of recovery of about 80% has been achieved. Tabular and graphic data are presented with recommendations for diagnostic applications. The immediate applications of these procedures are in implementing more effective detection and in preparing antigen for the immunologic studies that should provide the most sensitive detection.

Journal of the Fisheries Research Board of Canada

In vitro and in vivo efficacy of potentiated sulfonamide in control of furunculosis in salmonids

In vitro and in vivo efficacy of a potentiated sulffonamide, Ro5–0037, for inhibition of Aeromonas salmonicida , causative agent of fish furunculosis was determined. The components of the potentiated sulfonamide, sulfadimethoxine, and ormetoprim were tested alone and in combination. In vitro results showed that both sulfonamide-resistant and sensitive strains of A . salmonicida had greater sensitivity to Ro5–0037 than to either of its components. Also, sulfonamide-sensitive strains developed resistance to ormetoprim and sulfadimethoxine more rapidly than to Ro5–0037. Efficacy studies with small numbers of artificially infected trout revealed that Ro5–0037 effectively controlled furunculosis at 50 mg/kg of fish/day, one fourth the usual sulfonamide dosage level. Extensive field trials also showed the 50 mg/kg level of Ro5–0037 gave effective control of hatchery outbreaks of furunculosis. As found in the in vitro studies, all in vivo trials indicated the combination of ormetoprim and sulfadimethoxine was more efficient in inhibiting A . salmonicida than either component alone.

Journal of the Fisheries Research Board of Canada

Stress of formalin treatment in juvenile spring chinook salmon (Oncorhynchus tshawytscha) and steelhead trout (Salmo gairdneri>)

The physiological stress of 200 ppm formalin treatments at 10 C is more severe in the juvenile steelhead trout ( Salmo gairdneri ) than in the spring chinook salmon ( Oncorhynchus tshawytscha ). In the steelhead, a marked hypochloremia follows a 1-hr treatment and recovery requires about 24 hr. During longer treatments, hypercholesterolemia together with reduced regulatory precision, hypercortisolemia, alkaline reserve depletion, and hypocapnia unaccompanied by a fall in blood p H occur — suggestive of compensated respiratory alkalosis. In the spring chinook, hypochloremia and reduced plasma cholesterol regulatory precision are the significant treatment side effects but recovery requires only a few hours. Formalin treatments also cause epithelial separation, hypertrophy, and necrosis in the gills of both fishes but again, consistent with the physiological dysfunctions, these are more severe in the steelhead.

Journal of the Fisheries Research Board of Canada

Residues of DDT in lake trout (Salvelinus namaycush) and coho salmon (Oncorhynchus kisutch) from the Great Lakes

Concentrations of DDT residues were higher in lake trout ( Salvelinus namaycush ) from southern Lake Michigan in 1966–70 (average 18.1 ppm in fish 558–684 mm long) than in lake trout of the same size-class from Lake Superior in 1968–69 (4.4 ppm), and higher in adult coho salmon ( Oncorhynchus kisutch ) from Lake Michigan in 1968–71 (averages for different year-classes, 9.9–14.0 ppm) than in those from Lake Erie in 1969 (2.2 ppm). Residues were significantly higher in lake trout from southern Lake Michigan than in those from the northern part of the lake. In lakes Michigan and Superior, the levels increased with length of fish and percentage oil. In Lake Michigan coho salmon, the residues remained nearly stable (2–4 ppm) from September of the 1st yr of lake residence through May or early June of the 2nd yr, but increased three to four times in the next 3 mo. Residues in Lake Erie coho salmon did not increase during this period, which preceded the spawning season. Although the concentrations of total residues in whole, maturing Lake Michigan coho salmon remained unchanged from August 1968 until near the end of the spawning season in January 1969, the residues were redistributed in the tissues of the spawning-run fish; concentrations in the loin and brain were markedly higher in January than in August. This relocation of DDT residues accompanied a marked decrease in the percentage of oil in the fish, from 13.2 in August to 2.8 in January. Concentrations of residues were relatively high in eggs of both lake trout (4.6 ppm) and coho salmon (7.4–10.2 ppm) from Lake Michigan. The percentage composition of the residues ( p , p ′DDE, o , p ′/DDT, p , p ′DDT, and p , p ′DDT) did not differ significantly with life stage, size, age, or locality, or date of collection of lake trout or coho salmon.

Journal of the Fisheries Research Board of Canada

Comparison of protection in rainbow trout (Salmo gairdneri) inoculated with and fed Hagerman redmouth bacterins

Rainbow trout ( Salmo gairdneri ) fed 1.0 mg Hagerman redmouth bacterin per fish for 2 wk had no detectable specific, circulating, agglutinating antibody. In fish given a single subcutaneous inoculation of 1.0 mg of bacterin per fish, antibody was present from 3 wk later until 3 mo later, when the final sample was taken. Median lethal doses at various intervals after the bacterins were administered indicated that the inoculated fish could withstand a greater challenge by subcutaneous inoculation of the virulent bacteria than the orally immunized fish. The fish fed the vaccine lost their protection within 6 wk, whereas the inoculated fish had high levels of protection through 3 mo. The degree of protection was also confirmed by a "natural" exposure challenge.

Journal of the Fisheries Research Board of Canada

Pathophysiology of infectious hematopoietic necrosis virus disease in rainbow trout (Salmo gairdneri): early changes in blood and aspects of the immune Response after Injection of IHN Virus

Juvenile rainbow trout ( Salmo gairdneri ) were injected with infectious hematopoietic necrosis (IHN) virus and various hematological and blood chemical changes were monitored over 9 days. The packed cell volume, hemoglobin, red blood cell count, and plasma bicarbonate were significantly depressed by day 4. Plasma chloride, calcium, phosphorus, total protein, and blood cell types did not change during the 9 days. Furthermore, plasma LDH isozyme was significantly increased by the fourth day, and fish infected with infectious pancreatic necrosis virus, Vibrio anguillarum , Aeromonas salmonicida , and redmouth bacterium did not show specific LDH isozyme alterations. Acid-base alterations occurred at 10 C but not at 18 C. The acid-base imbalance and elevation of the LDH isozyme were consistently associated with the early development of the disease.The immune response after injection of IHN virus was determined and protection from disease was tested by passive immunization. Actively immunized fish developed IHN-neutralizing antibodies within 54 days after injection of virus, and the antibodies were protective when juvenile fish were passively immunized and experimentally challenged with IHN virus.

Journal of the Fisheries Research Board of Canada

Fish sporozoa: Extraction of antigens from Myxosoma cerebralis spores which mimic tissue antigens of rainbow trout (Salmo gairdneri)

This is the first report of an antigenic preparation from the spore stage of any histozoic sporozoan parasite. The method for successful extraction of the antigens is presented. This antigenic preparation is active in rabbits, but not salmonid fish. The detection of asymptomatic carrier fish using the spore antigens was not successful and evidence is presented to show that the parasite is successful because its antigens mimic those of trout. Immunoelectrophoresis indicates the parasite and trout antigens are different proteins.

Journal of the Fisheries Research Board of Canada

Myxosoma cerebralis: Comparative sensitivity of spore detection methods

Physical and biophysical methods of detecting spores of Myxosoma cerebralis were used in sequence on 87 individual fingerling rainbow trout ( Salmo gairdneri ) from two populations with a low incidence of infection. Physical methods of releasing spores from the organs of equilibrium, gill arches, or the axial skeleton gave an estimated rate of infection of 2.3–4.6%. Each succeeding step — pepsin digestion, trypsin digestion, and differential centrifugation through 55% dextrose solution — revealed additional infected fish. The final step of the sequence detected 10.5 times more infected fish than were found by examination of the organs of equilibrium or the axial skeleton with physical means; the true incidence was at least 24.1%. Procedures are described for using biophysical methods on 60-fish pools for hatchery inspection work and also on the more bony skeletons of mature fish.

Journal of the Fisheries Research Board of Canada

Effect of temperature on accumulation of methylmercuric chloride and p,p'DDT by rainbow trout (Salmo gairdneri)

Amounts of mercury and DDT residues accumulated from water by yearling rainbow trout ( Salmo gairdneri ) in the laboratory increased as water temperature increased. Fish exposed to methylmercuric chloride at concentrations of 234&ndash;263 parts per trillion for 12&ensp;wk at 5, 10, and 15&ensp;C accumulated 1.19, 1.71, and 1.96&ensp;ppm; fish exposed to p , p &prime;DDT at concentrations of 133&ndash;176 parts per trillion accumulated 3.76, 5.93, and 6.82&ensp;ppm. Concentrations of mercury accumulated by the fish were significantly different ( P &ensp;<&ensp;0.01) at each of the three temperatures, and the concentrations of DDT were significantly different at 5 and 10 and 5 and 15&ensp;C. Throughout the period of exposure, the concentration factors (concentration of contaminant in the fish/concentration in water) at each of the three temperatures were far higher for p , p &prime;DDT than for methylmercuric chloride.

Journal of the Fisheries Research Board of Canada

Effect of feeding brown trout (Salmo trutta) a diet pelleted in dry and moist forms

Growth rate, body composition, and intake of either dry matter or energy did not differ significantly ( P > 0.05) between two groups of juvenile brown trout ( Salmo trutta ) fed either a low- or high-moisture semipurified diet at different rates to compensate for a diet energy density gradient. Feed/gain efficiency, on an as-fed basis, was significantly greater ( P < 0.01) in fish fed the low-moisture diet, but did not differ ( P > 0.05) when compared on the basis of dry matter or energy intake.

Journal of the Fisheries Research Board of Canada

Amino acid supplementation of casein in diets of Atlantic salmon (Salmo salar) fry and of soybean meal for rainbow trout (Salmo gairdneri) fingerlings

Fry of Atlantic salmon ( Salmo salar ) fed a diet containing isolated fish protein grew significantly faster than those fed a diet containing casein without supplemental amino acids, and had improved feed conversion and lower mortality. Supplementing the casein diet with essential amino acids to the levels in the isolated fish protein diet significantly increased growth rate, reduced mortality, and improved feed conversion.When fingerling rainbow trout ( S . gairdneri ) were fed diets containing soybean meal as the sole source of protein, additions of amino acids to simulate those levels of essential amino acids in trout eggs and isolated fish protein significantly improved growth. Additions of methionine, lysine, histidine, and leucine individually and in several combinations had no effect.

Journal of the Fisheries Research Board of Canada

Life histories and abundance of crustacean zooplankton in the outlet of Lake Superior, 1971-72

In sampling throughout a year, at about 3-wk intervals, of the crustacean zooplankton discharged from Lake Superior through the St. Marys River, 30 species were collected, including three not previously recorded for the lake: the copepod Cyclops strenuus , and the cladocerans Alona costata and Alonella acutirostris . Five copepods, Cyclops bicuspidatus thomasi , Diaptomus ashlandi , D . sicilis , Limnocalanus macrurus , and Senecella calanoides were present in the plankton throughout the year while three other copepods, Diaptomus minutus , Epischura lacustris , and Mesocyclops edax , along with all cladocerans, were present only during summer and fall. Five species of copepods, Diaptomus sicilis , D . minutus , Limnocalanus macrurus , Senecella calanoides , and Epischura lacustris produced a single generation annually; three other copepods and all cladocerans produced two or more generations. All species breed 1–3 mo later in Lake Superior than in lakes Michigan and Erie.

Journal of the Fisheries Research Board of Canada

Statistical methods for estimating normal blood chemistry ranges and variance in rainbow trout (Salmo gairdneri), Shasta Strain

Gaussian and nonparametric (percentile estimate and tolerance interval) statistical methods were used to estimate normal ranges for blood chemistry (bicarbonate, bilirubin, calcium, hematocrit, hemoglobin, magnesium, mean cell hemoglobin concentration, osmolality, inorganic phosphorus, and pH for juvenile rainbow ( Salmo gairdneri , Shasta strain) trout held under defined environmental conditions. The percentile estimate and Gaussian methods gave similar normal ranges, whereas the tolerance interval method gave consistently wider ranges for all blood variables except hemoglobin. If the underlying frequency distribution is unknown, the percentile estimate procedure would be the method of choice.

Journal of the Fisheries Research Board of Canada

Effects of pH on toxicity of antimycin to fish

Detoxification of antimycin at pH 9.5 was caused by two factors. The piscicide was biologically unavailable at the high pH, and this unavailability was reversed by decreasing the pH of water solutions. Simultaneously antimycin detoxified with time, and the resulting loss in toxicity was irreversible. The toxicity of antimycin was related to the amount of un-ionized molecules; however, the dissociation curve resulting from the published pKa of 5.1 does not agree with the implied dissociation when based on toxicity. Toxicity of antimycin decreased gradually from pH 6.5 to 8.5 and abruptly from 8.5 to 9.5 with carp ( Cyprinus carpio ), green sunfish ( Lepomis cyanellus ), and bluegill ( Lepomis macrochirus ). As previously suggested, water hardness had little or no effect on toxicity.

Journal of the Fisheries Research Board of Canada

Bacterial diseases of fishes: Diagnostic procedures for gram-negative pathogens

A diagnostic scheme employing 10 media, 4 reagents, and 5 specific antiserums has been devised for identification of gram-negative pathogens of fishes. The scheme is not intended for detailed speciation of organisms, but for generic identification of organisms associated with infected fishes. Diagnosis can be accomplished in 24 h with selective media and antiserums, and in no more than 72 h with other media and reagents.

Journal of the Fisheries Research Board of Canada

Phoma herbarum , a fungal plant saprophyte, as a fish pathogen

Phoma herbarum , a fungal plant saprophyte, was isolated from diseased hatchery-reared coho salmon ( Oncorhynchus kisutch ), chinook salmon ( O . tshawytscha ), and rainbow trout ( Salmo gairdneri ). The disease was observed at 10 national fish hatcheries in Washington and Oregon, but the low incidence of experimental infections indicate that it is only weakly contagious. Histopathological examination suggests that the air bladder is one of the primary organs infected. The visceral organs are also affected in both natural and experimental infections.

Journal of the Fisheries Research Board of Canada