Proliferative kidney disease in rainbow trout Salmo gairdneri Richardson

Abstract. Two entirely separate outbreaks of PKD are described in an attempt to properly define the condition and enable it to be differentiated from other diseases of a similar nature. Losses of up to 75% of fingerling rainbow trout were recorded in one outbreak, illustrating the potentially serious nature of the disease. Although the kidneys showed the most obvious pathological changes, other organs were also affected. The host response was granulomatous in type, the foci of each cellular reaction being 5-20 μm eosinophilic cells considered to be parasitic. The cytoplasm of these cells contained numerous electron dense bodies some with a tail, but each with an electron lucent bar always orientated at right angles to the plasmalemma whenever they were near it. The most obvious cytoplasmic inclusion of these 'parasites' were other cells numbering up to five or six, each with its own nucleus and nucleolus, but devoid of any of the small electron dense bodies. The significance of either of these inclusions is unknown.
A limited differential diagnosis is given, and the argument presented that the condition PKD is the result of infection by a parasite, possibly an amoeba, in combination with poor quality water.     

Further consideration of the haematology of proliferative kidney disease (PKD) in rainbow trout, Salmo gairdneri Richardson

Abstract. A study of selected haematological parameters in rainbow trout, Salmo gairdneri Richardson, exposed to proliferative kidney disease (PKD) under field conditions is described. Changes in the blood picture are related to kidney pathology at different stages of the disease. As extensive renal vascular pathology, haemoglobin crystallization and inflammatory lesions developed, there were progressive decreases in haemoglobin and packed cell volume values, erythrocyte numbers declined to less than 50% of those in control fish, and numbers of misshapen erythrocytes increased. Leucopenia, neutrophilia and thrombocytopenia developed, especially in oedematous fish. With recovery, most values were similar to those of control fish. In recovered, re-challenged fish, erythrocyte counts, packed cell volume and haemoglobin values decreased in infected fish compared with uninfected fish. The results of the study are compared with those of other authors and the type of anaemia in PKD is discussed.     

Strawberry disease in rainbow trout, Salmo gairdneri Richardson

Abstract. Strawberry disease is a subchronic, non–debilitating, and non–fatal inflammatory skin disease of rainbow trout that has been recognized for the past 25 years. Morbidity ranges up to 80% and the disease affects fishes from 15cm in length to brood stock size. Epizootiological data indicate that strawberry disease usually appears, first in the autumn and reaches peak incidence during the following winter and spring. Data also indicate that the disease is found only in certain trout farms in the western and Pacific north–western regions of the United States. Although the cause of strawberry disease is unknown, the normal clinical course of 8 weeks can be reduced by oral treatment with oxytetracycline. Clinical signs include appearance of bright red, raised, circumscribed, ulcerated and indurated lesions in the skin that usually range up to 3 cm or more in diameter. Microscopically, the disease is characterized as a subchronic, focal, non–suppurative dermatitis with ulceration and extensive infiltration of mononuclear inflammatory cells.     

Genetic variance for growth in rainbow trout (Salmo gairdneri)

The possibilities of genetic improvement of growth of rainbow trout were investigated. Two half-diallel crossing experiments with three strains were performed. In the second experiment families within a strain or strain combinations could be identified. One hundred fish of each strain, strain cross or family were measured at five or four different ages. Differences between strains, crosses and between families within each of them were highly significant at all ages. In juvenile stages heterosis seemed to be present, although it was not statistically significant. Differences between strains became more pronounced as age advanced. Genetic variance within strains and strain crosses was large and appeared to increase with age. Genetic improvement by selection appears promising provided mass selection is not performed too early. The small F-values of preliminary expt. 2 may indicate strong competition within each group which tends to increase residual variability.     

Protein sparing effects in large rainbow trout,Salmo gairdneri

Large rainbow trout (250–550 g) were fed to satiation or 0.5% live weight/day, one of six balanced diets varying in protein (30%, 43%, 52%) and lipid levels (12%, 24%). Growth and changes in body composition were measured over a 60-day feeding period. Mean appetite varied inversely with dietary digestible energy. Total weight gain over the 60-day period was not significantly different (P = 0.05) for fish fed to satiation on diets containing 43 or 52% protein at the 24% lipid level. Weight gain was significantly lower among fish fed to satiation on the 30% protein, 12% lipid diet than those fed diets containing 43 and 52% protein, at either lipid level. When feeding level was limited to 0.5% of live body weight/day, weight gain was significantly higher for those fish fed diets containing 43 or 52% protein and 24% lipid, than fish fed all other diets. An increase in dietary lipid from 12 to 24% resulted in a significant increase in gross conversion efficiency of both dietary energy and protein, at all three dietary protein levels when fish were fed to satiation. A similar trend resulted when feeding level was reduced to 0.5% live weight/day. Dietary protein concentration did not significantly affect gross conversion efficiency of protein within either feeding rate. Increasing dietary protein tended to result in an increase in gross conversion efficiency of lipid at both dietary lipid levels within each feeding rate.     

Proliferative kidney disease (PKD) of salmonids

Proliferative Kidney Disease (PKD) of salmonids, pathology, occurrence and the causative agent are described according to recent literature. For diagnosis histology and/or impression smears of infected kidneys are recommended. Original coloured photos are added to serve this purpose.     

Epidemiological aspects of proliferative kidney disease amongst rainbow trout Salmo gairdneri Richardson in Northern Ireland

Abstract. The epidemiology of PKD is described as it relates to one affected farm in Northern Ireland. From 1972–1976 stocking and management practices led to mortality of 10–15% amongst the 0+fish. 1+or older fish were never affected. In 1977 and 1978, however, delaying the stocking of the farm until July eliminated deaths in the 0+fish, and mortality in these 1977-moved fish the subsequent year remained at an absolute minimum. Preliminary observations suggest that a means of controlling the disease has been found.
Experimental work demonstrates that the resistance of 1 +or older fish is due to previous exposure and is not an age-related immunity. Experimental work also suggests the presence of an incubation period of 6–7 weeks and that the peak time of infectivity is probably around May. None of the evidence detracts from the possibility that an infectious agent is involved although an attempt to transmit the disease failed.     

The effect of water pH on swimming performance in rainbow trout (Salmo gairdneri,Richardson)

A Brett-type respirometer was used to measure the effect of water pH on swimming performance of rainbow trout (Salmo gairdneri). Variations in water pH between 6 and 9 had no measurable effect on maximum aerobic swimming speed. At water pH 4, 5, and 10, however, the critical velocity was only 55, 67, and 61% respectively of that recorded for fish in water of pH 7. Exposure to acid conditions increased coughing and breathing frequency. Acid exposure resulted in a decrease whereas alkaline exposure resulted in an increase in both whole blood and red blood cell pH. Blood gas and acid-base characteristics showed little change during swimming at 2.0 BL/second, but exhaustive swimming resulted in a marked and immediate drop in blood pH in fish in acid, alkaline and neutral water. The blood acid-base status was restored to resting levels after exercise in neutral and alkaline water, but the acidosis was maintained following exercise in acid water. Fatigue occurred earlier and blood lactate levels increased to a higher level in fish swum to exhaustion in acid or alkaline water, compared with fish in neutral water.     

Thyroidal compensation in rainbow trout (Salmo gairdneri) fed canola meal

Rainbow trout (Salmo gairdneri Richardson) were fed either a soybean mealbased (SM) or canola meal-based (CM) diet for up to 20 weeks. Plasma thyroxine (T₄) and triiodothryonine (T₃) levels were significantly lower in the CM-fed fish sampled after 12 weeks. However, there appeared to be some compensation after 12 and 20 weeks in that the thyroid hormone levels in trout fed the CM were not significantly different from those of the SM-fed fish. Nevertheless, there was marked thyroid hyperplasia and hypertrophy in the CM-fed fish sampled at 12, 16 and 20 weeks after commencement of the experiment. Moreover, the growth rate was significantly lower in the CM-fed fish in comparison to the SM-fed fish throughout the 20 week study period.Plasma T₄ levels were similar in SM-fed fish sampled 12, 16 and 20 weeks after commencement of the experiment, but plasma T₃ levels progressively increased over this period, as did the apparent activity of the thyroid tissue based on histological criteria.Fasting for up to 8 weeks resulted in the arrested growth of the SM-fed fish, and a loss in body weight of the CM-fed animals over the 8 week period of the fast. In addition, the plasma thyroid hormone levels in the fasted fish tended to be lower than in fish fed both the SM and CM diets prior to fasting, and there was histological evidence indicating a reduced activity of the pituitary-thyroid axis. However, thyroid hyperplasia and hypertrophy were still evident in the fasted fish previously fed the CM diet indicating that the adverse affects of CM diets are not completely reversible after 8 weeks.In fish fed the CM diet for 12 weeks and then the SM diet for up to a further 8 weeks (diet C-S) there was a compensatory increase in plasma thyroid hormone levels evident within 4 weeks after the change in diet, but no apparent decrease in thyroid hyperplasia or hypertrophy. In addition, in the fish fed the C-S diet there was a marked compensatory growth rate, and an increased feed: gain ratio; body weights of this group of fish were not significantly different from those of the SM-fed animals after 20 weeks of study, indicating a considerably higher growth rate over the last 8 week period.     

Immunization of rainbow trout, Salmo gairdneri Richardson, against bacterial kidney disease: preliminary efficacy evaluation

Abstract. A bacterin for immunization against bacterial kidney disease of salmonid fishes caused by Renibacterium salmoninarum is described. Cultures were grown in Evelyn's KDM2 medium containing 10% calf serum in a fermenter under the following conditions: pH 7.2, 15°C, 800ml/min air, 200 rev/min agitation and 5–15 days of incubation. Possible substitutes for calf serum were 10% horse serum 0.15% starch and leptospira medium. The bacterins were inactivated with 0.3% formalin and no adjuvants were used. Other tests evaluated pH-lysed bacterin, 50% concentrated bacterin and 50% concentrated pH-lysed bacterin. Juvenile rainbow trout, salmo gairdneri Richardson, were vaccinated either by intraperiotoneal (i.p.) injection, 2 min immersion or 2-step hyperosmotic infiltration. Fish were held from four to six weeks at 11°C, then challenged by i.p. injection with the homologous virulent bacterium. Fish died from days 19 to 40 after challenge. The best preparation was pH-lysed bacterin given by a single i.p. injection; hyperosmotic and immersion vaccination were not effective. Typically when 80% or more of unvaccinated controls were infected as detected by Gram stain, 10% or less of the vaccinated fish were infected.     

Evaluation of antimicrobial compounds for the control of bacterial kidney disease in rainbow trout, Salmo gairdneri Richardson

Abstract From a comparison of over 70 antimicrobial compounds by in vitro and in vivo methods, it was found that clindamycin, erythromycin, kitasamycin, penicillin G and spiramycin could be used successfully for combating early clinical cases of bacterial kidney disease (BKD) in rainbow trout, Salmo gairdneri Richardson. In addition, cephradine, lincomycin and rifampicn were effective for chemoprophylaxis of BKD, although they were of no use for therapeutic purposes.     

水温对虹鳟血清无机微量元素含量影响的初步研究

使用日立7170A全自动生化分析仪和贝克曼CX-3电解质分析仪,检测不同水温虹鳟血清中无机微量元素含量.结果表明,水温14～23℃,虹鳟血清中铜元素含量比鳙鱼随水温变化显著,钾、磷、钙、钠、氯元素含量变化不显著.分析了虹鳟在温水环境中血清无机微量元素含量的变化规律.     

Immunoglobulin heterogeneity in the rainbow trout, Salmo gairdneri Richardson

Abstract. Hetereogeneity of rainbow trout immunoglobulins was demonstrated by using monoclonal antibody 1A6 and polyacrylamide-gradient gel electrophoresis. Immunoglobulins defined by elisa using monoclonal antibody 1A6 were about 30% of the total immunoglobulins, detected by elisa using polyclonal antibodies, in healthy rainbow trout. In trout obtained from farms with a previous history of infectious viral diseases, 1A6-immunoglobulins were only about 14% of the total. Several serum pools from infected trout could be totally depleted of 1A6-immunoglobulins (about 12% of total immunoglobulins) by affinity chromatography over Sepharose immobilized monoclonal antibody 1A6. Polyacrylamide-gradient gel electrophoresis under denaturing conditions of total immunoglobulins, 1A6 immunoglobulins and no-1A6 immunoglobulins purified by affinity chromatography, showed a majority heavy chain of 70 KDa and a minority heavy chain of about 60 KDa, two light chains of 24 and 26 KDa, and a 11–14 KDa polypeptide.