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1.
Abstract

The cellular inflammatory response of rainbow trout Oncorhynchus mykiss (formerly Salmo gairdneri) to the myxozoan parasite PKX that causes proliferative kidney disease was investigated. The response was studied from 3 to 20 weeks after the fish were injected with infected kidney homogenate. Kidney samples were examined by light and electron microscopy. In contrast to most myxosporeans, PKX provoked a severe host response. Parasites were found in peritubular capillaries and sinusoids 3 weeks postinjection. The initial response to PKX was hemopoietic hyperplasia followed by a marked granulomatous nephritis that was resolved by termination of the study at 20 weeks postinjection. The macrophage was the predominant cell type involved in the inflammatory response to PKX. We presume that the macrophage effectively interrupts the development of PKX and eliminates the parasite from the host.  相似文献   

2.
Differences in susceptibility to the myxozoan parasite Tetracapsuloides bryosalmonae, the causative agent of proliferative kidney disease (PKD), between four strains of rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta) were evaluated. Fish were exposed to water enzootic for the parasite in the field for 5 days and were subsequently transferred to the laboratory. Relative parasite load was determined after 2, 3 and 4 weeks post-exposure (wpe) by quantitative real-time PCR (qPCR) of kidney samples and number of parasite stages was determined in immunohistochemical stained sections of kidney, liver and spleen tissues. According to qPCR results, the highest amount of parasite DNA per equal amount of host tissue at all time points was measured in brown trout. Two of the rainbow trout strains showed lower relative parasite load than all other groups at the beginning of the experiment, but the parasite multiplied faster in these strains resulting in an equal level of relative parasite load for all rainbow trout strains at 4 wpe. A weak negative correlation of fish size and parasite load was detected. Only in samples of a few fish, single stages of T. bryosalmonae were found in sections stained by immunohistochemistry impeding quantitative evaluation of parasite numbers by this method. The results indicate a differential resistance to T. bryosalmonae between the rainbow trout strains investigated and between rainbow trout and brown trout.  相似文献   

3.
Abstract

Blood parameters, disease resistance, and the immune response were sequentially evaluated in rainbow trout Oncorhynchus mykiss with proliferative kidney disease (PKD). The fish were maintained under laboratory conditions, and the study group went through a full cycle of the disease. Hematological and serological changes occurred primarily in those fish with severe kidney lesions. Fish infected with the parasite that causes PKD demonstrated a greater resistance to bacterial challenge, and their immune responses were heightened when compared with those of uninfected fish. These data suggest that PKD alone is not a predisposing factor for secondary infections if the fish does not incur severe renal lesions.  相似文献   

4.
Samples from 5 Danish freshwater trout farms rearing rainbow trout (Oncorhynchus my kiss) were examined for parasite infections from October 1993 until November 1994 and recorded parasites are listed. In addition, results from an examination of a mariculture net cage system are presented as well. A total of 10 metazoan and 10 protozoan parasites were recorded. The metazoans included Gyrodactylus derjavini, Gyrodactylus salaris, Eubothrium crassum, Triaenophorus nodulosus, Proteocephalus sp., Diplostomum spathaceum, Tylodelphus clavata and Argulus foliaceus from the freshwater farms. The protozoans Hexamita salmonis, Ichthyobodo necator, Ichthyophthirius multifiliis, Apiosoma sp., Epistylis sp., Trichodina nigra, T. mutabilis, T. fultoni, Trichodinella epizootica, and an Ichthyophonus like intestinal parasite were also detected in the freshwater trout farms. Based on lectin binding studies, few fish were found positive for the myxosporean parasite PKX although no clinical cases were reported. In the mariculture system, Lepeophtheirus salmonis and Caligus elongatus were found.  相似文献   

5.
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.  相似文献   

6.
Abstract

A nonradioactive in situ hybridization (ISH) protocol was developed to detect Myxobolus cerebralis, the causative organism of whirling disease, in its primary host, rainbow trout Oncorhynchus mykiss, and in its alternate oligochaete host, Tubifex tubifex. A cocktail of three oligonucleotide primers (derived from the small subunit ribosomal DNA sequence) directed at target sequences of the parasite DNA was tailed at the 3′ end with digoxigenin-labeled deoxyuridine triphosphate (DIG-dUTP). Labeled probes were hybridized to parasite DNA present in deparaffinized tissue sections from infected trout and oligochaetes. The bound probes were visualized after modifications of existing ISH protocols. By using the new ISH procedure, the parasite was found in target tissues of subclinically and clinically infected fish and tubificid oligochaetes after exposures of these hosts to triactinomyxons and mature spores, respectively. The probe did not bind with salmonid tissues infected with two other myxosporean parasites, Ceratomyxa shasta or the PKX organism, or to a Myxobolus sp. infecting the cartilage of plain sculpin Myoxocephalus jaok. These initial results indicate that ISH is an effective and specific test for detecting Myxobolus cerebralis in its fish and oligochaete hosts.  相似文献   

7.
Although rainbow trout fry mortality syndrome caused by the bacterium Flavobacterium psychrophilum is widespread in fish farms it is difficult to reproduce infection of rainbow trout in the laboratory using immersion exposure with bacterial suspensions. It has therefore been speculated that ectoparasites could act as enhancers of bacterial infections under natural conditions. In the present study rainbow trout fry were exposed to infections with F. psychrophilum (immersion for 30 min or 10 h) alone, exposed to the ectoparasitic monogenean Gyrodactylus derjavini alone or exposed to both pathogens in combination. Infection levels and host mortality were subsequently monitored to elucidate if the ectoparasitic monogeneans could enhance infection of fish with the bacterium. Immersion of fish in bacterial suspensions alone did not result in infection. Only one fish became infected with the bacterium and this fish belonged to the combination exposure group. The parasite populations increased differently in the various groups and it was found that host mortality was correlated to gyrodactylid infection levels (r=0.94) but not to bacterial exposure. The results emphasise the pathogenicity of the parasite G. derjavini, the relative resistance of intact fish to direct exposure to F. psychrophilum but provide only a weak indication of a possible enhancement of bacterial invasion due to ectoparasitic infections. It cannot be excluded that higher parasite burdens and/or prolonged immersion (more than 10 h) in bacterial suspensions may result in bacterial invasion.  相似文献   

8.
Abstract

We determined the sensitivity and specificity of a nested polymerase chain reaction (PCR) for detection of the microsporidian parasite Nucleospora salmonis in kidney tissue of rainbow trout Oncorhynchus mykiss. Kidney tissues were sampled on three dates from 162 juvenile rainbow trout obtained from a California State fish hatchery where the organism was endemic. Kidney tissues were used to prepare imprints stained with May–Grünwald Giemsa and for extraction of genomic DNA for a nested PCR test for N. salmonis. Positive PCR results for N. salmonis were obtained from 1 of 100, 2 of 32, and 27 of 30 kidneys collected on the first, second, and third sample dates, respectively. Kidney tissues from 3 of 27 trout in the third sample that tested positively by PCR also had microscopic evidence of parasites in stained kidney imprints. No parasites were detected in the remaining 159 kidney samples examined microscopically. Sensitivity and specificity of the PCR assay were estimated by using maximum likelihood estimation based on cross-classified test results. This method yielded estimates of sensitivity of 99.99% and specificity of 99.87%. This field evaluation supports experimental evidence that the nested PCR test will be a valuable diagnostic tool for prevention and control of N. salmonis as well as for risk assessment associated with fish movements.  相似文献   

9.
The immunomodulatory effects of beta-endorphin were studied by measurements of the production of superoxide anion, phagocytosis and chemotaxis of kidney phagocytic cells in rainbow trout, Oncorhynchus mykiss. The production of superoxide anion in phagocytic cells increased significantly in rainbow trout injected with chum salmon beta-endorphin. The responses were dose-dependent. The phagocytosis and chemotaxis also significantly increased in kidney phagocytic cells of rainbow trout injected with alpha-endorphin. These results show that beta-endorphin in rainbow trout activates the function of phagocytic cells in vivo.  相似文献   

10.
Kidney disease is a common and serious condition in domestic cats. There are numerous causes of kidney disease including parasitic infection. Encephalitozoon cuniculi is a microsporidian parasite that develops in the kidneys of rabbits and causes chronic renal disease. Little has been reported concerning E. cuniculi in cats and no serological studies on this parasite in cats have been conducted in the United States to date. The present study explored the possibility that E. cuniculi is an unrecognized contributor to the high prevalence of kidney disease observed in cats. A serological survey was conducted to determine the prevalence of IgG antibodies to spores of E. cuniculi in cats with and without a diagnosis of chronic kidney disease (CKD) according to the International Renal Interest Society (IRIS) staging system. Likewise, samples were examined for IgG antibodies to Toxoplasma gondii, a common well studied protozoan of cats. Plasma and sera were obtained from 232 feline patients at the Virginia-Maryland Regional College of Veterinary Medicine teaching hospital. With the investigators blinded to the renal status of test subjects, samples were screened via indirect immunofluorescent antibody assay (IFA). Thirty-six of the 232 cats met the IRIS staging system criteria for CKD. Antibodies to E. cuniculi were found in 15 of the 232 samples, which included 4 of the 36 cats with CKD. Sera from cats serologically positive to E. cuniculi did not react to spores of E. intestinalis or E. hellem when examined in the IFA. Antibodies to T. gondii were found in 63 of the 232 samples, which included 10 of the 36 cats with CKD. The prevalence of antibodies in cats with CKD to either protozoan was not significantly different (P>0.05) from the cats without CKD in the study. Collectively the results do not support the hypothesis that either E. cuniculi or T. gondii play a significant etiologic role in the occurrence or progression of CKD in cats.  相似文献   

11.
From early April into mid-June 1977, sequential groups of juvenile rainbow trout (Oncorhynchus mykiss) and brown trout (Salmo trutta) were each exposed for 10 days to the parasite Myxobolus cerebralis by immersion in a stream inhabited by infected wild trout. Following incubation in a M. cerebralis-free facility, trout were subsequently killed, and heads and gill arches were examined by routine histologic methods. A grading scale to quantify lesion severity was developed and applied. Percentage infected, lesion severity scores, effects of water temperature and flow rates on percentage infected and lesion severity scores, and resulting pathology were determined for each species at each exposure period. The percentage of rainbow trout infected with M. cerebralis was significantly higher than the percentage of brown trout infected for each exposure period. The percentages of rainbow trout infected in exposure periods later in the calendar year were significantly higher than those in earlier periods. The percentages of brown trout infected were not significantly different among exposure periods. Overall average lesion severity scores were significantly higher in rainbow than in brown trout. Lesion severity scores in rainbow trout increased over time (a positive correlation with exposure period). Lesion severity scores were not significantly different for brown trout among exposure periods. A significant correlation existed between water temperature and percentage of rainbow trout infected; a significant correlation also existed between water temperature and lesion severity scores in rainbow trout. Similar correlations did not exist for percentage of brown trout infected or accompanying lesion severity scores. In rainbow trout, ventral calvarium was the most common site of M. cerebralis replication, followed by gill arches. In brown trout, lesions were virtually confined to gill arches. Early lesions consisted of foci of cartilage necrosis with small numbers of M. cerebralis developmental stages. More advanced lesions consisted of multifocal areas of cartilage necrosis with numerous M. cerebralis developmental stages and/or mature myxospores bordered and/or infiltrated by mono- and multinuclear leukocytes. Lesions in brown trout were smaller and had fewer associated leukocytes and M. cerebralis developmental stages and/or mature myxospores. Higher infection rates, lesion severity scores, and differences in lesion location in rainbow versus brown trout explain in part why numbers of rainbow but not brown trout have fallen in western rivers inhabited with M. cerebralis-infected trout.  相似文献   

12.
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13.
Following a per os challenge of naive rainbow trout with live spores of Loma salmonae, head kidney mononuclear cells (MNC) in culture were able to proliferate in response to crude soluble parasite extract or intact dead spores. A significant response was seen by week 2 post-exposure and a maximum response developed by week 6 or 8, respectively. During this initial challenge, spore filled cysts developed on the gills of challenged fish, and the cysts ruptured by week 12 as is typical for microsporidial gill disease of salmonids (MGDS). Two weeks following this, fish were re-challenged with live spores, and in these fish an enhanced in vitro proliferative response of MNC was immediately apparent, and spore filled cysts did not develop. In contrast, when naive trout were given dead spores by intraperitoneal injection, the most pronounced proliferative responses of MNC developed earlier (week 2 PE) and the response was greater when cells were incubated in vitro with dead spores rather than with crude soluble extract. When these fish were re-challenged per os with live spores, a heightened proliferation in MNC was observed 4 weeks after this exposure and the fish likewise resisted development of xenomas. In fish infected orally or injected intraperitoneally with spores, a marked increase in the response to the mitogen concanavalin A was seen for 22 weeks post-exposure when compared to controls not receiving any spores.  相似文献   

14.
A whirling-disease-resistant strain of rainbow trout Oncorhynchus mykiss (GRHL strain) derived from a backcross of an F1 hybrid of two strains (German strain x Harrison Lake strain) with German strain females, was compared with the Ten Sleep (TS) strain of rainbow trout. The GRHL strain had consistently superior growth and feed conversion in two consecutive hatchery trials. Hatching and mortality rates were similar between strains. Both strains were stocked into two Utah reservoirs (Hyrum, Porcupine), and a third, Causey Reservoir, was monitored as a control for seasonal variation in prevalence of Myxobolus cerebralis. A total of 1,323 salmonids captured by gill net in spring and fall sampling between 2006 and 2008 were tested for M. cerebralis via pepsin-trypsin digest methods. Only eight of these (< 1% per species) had clinical signs consistent with whirling disease. In both reservoirs, GRHL survived better than the TS and had higher growth rates. The prevalence of M. cerebralis was significantly lower for GRHL (18.1%) than TS (50.0%) in Porcupine Reservoir. In Hyrum Reservoir the trend was similar, but prevalence was lower and did not significantly differ between GRHL (9.6%) and TS (23.1%). For infected fish, no significant differences were observed between strains in myxospore counts in either Hyrum (GRHL = 911-28,244 spores/fish [spf], TS = 1,822-155,800 spf) or Porcupine (GRHL = 333-426,667spf, TS = 333-230,511 spf) reservoirs. Unmarked rainbow trout in both reservoirs had significantly higher myxospore counts than stocked fish of either strain. There were significant differences in M. cerebralis prevalence and myxospore loads among other naturally reproducing salmonids in the reservoirs. The trend in susceptibility was cutthroat trout Oncorhynchus clarkii > kokanee Oncorhynchus nerka > brown trout Salmo trutta. The GRHL performed well in both hatchery and field settings and is recommended for stocking programs.  相似文献   

15.
OBJECTIVE: To investigate immunostimulating activity of purified rainbow trout (Oncorhynchus mykiss) C-reactive protein (CRP) on trout phagocytic cells. ANIMALS: 20 rainbow trout and 2 rabbits. PROCEDURE: The effect of CRP on phagocytic activity of head kidney (HK) cells was examined by use of a phagocytosis assay with plastic particles. The enhancing effect of CRP on migration activity of HK cells was examined by use of the blind well assay. RESULTS: Glass-adherent cells from clinically normal trout had increased dose-dependent phagocytic activity against plastic particles when cells were incubated in the presence of CRP. Pretreatment of particles with CRP also enhanced phagocytic activity of the cells, indicating an opsonic effect of CRP. Rabbit anti-trout CRP serum suppressed the enhancing activity of CRP. The HK cells had significant dose-dependent chemokinetic activity against CRP that was not inhibited by anti-CRP serum, indicating that a CRP-antibody complex also could be chemokinetic. CONCLUSIONS: Rainbow trout CRP has immunostimulating activity for HK cells, resulting in enhanced phagocytic and chemokinetic activities.  相似文献   

16.
Young-of-the-year rainbow trout clinically affected by proliferative kidney disease (PKD), a systemic protozoan infection, exhibit a massive proliferation of small lymphocytes in the posterior kidney and spleen, a decrease in erythrocyte packed cell volume, hemoglobin, and serum albumins and an increase in beta-globulins. Electronphotomicrographs of the causative agent indicate that it is engulfed within a macrophage which is surrounded by small lymphocytes. Fish having survived a clinical episode are completely refractory to subsequent infection. Their serum electrophoretic patterns are quite unremarkable.  相似文献   

17.
The results of a series of experiments to investigate the use of the arylmethane dye, malachite green, for the control of proliferative kidney disease in rainbow trout (Salmo gairdneri Richardson) are described. Under field conditions using the bath application method the dye gave good control of the disease with treatments at 1.6 ppm for 40 minutes repeated at seven, 14 and 21 day intervals. Flush treatments were also successful using the same treatment intervals and beginning with 3.2 ppm malachite green. The problems of toxicity and of standardising the exposure of the fish to the dye with flush treatments are discussed.  相似文献   

18.
Discovery of fish exhibiting clinical signs of ceratomyxosis in Washington State prompted concern over the potential impact of the myxozoan parasite Ceratomyxa shasta on native stocks of steelhead Oncorhynchus mykiss (anadromous rainbow trout). To investigate these concerns, a survey of 16 freshwater systems within the Puget Sound watershed, including Lake Washington, was conducted by sentinel exposure of susceptible fish (cutthroat trout O. clarkii and rainbow trout). Fish were exposed for 7 d during September 2003 and May 2004 and then were returned to a holding facility for monitoring of disease signs. Mortality caused by the parasite occurred only in the exposure group held at the University of Washington Hatchery, which receives its water from Portage Bay of Lake Washington. Fish from all other sites were negative for C. shasta, both visually and by polymerase chain reaction (PCR) assay, except for a single fish held at the Tumwater Falls Hatchery in September 2003. A single deformed spore was detected in that fish, but infection could not be confirmed by PCR and the parasite was not detected from any other fish held at that site during either the September or the May exposure. From these results, we conclude that C. shasta is not likely to have contributed significantly to the decline of steelhead populations throughout Puget Sound.  相似文献   

19.
Abstract

Juvenile rainbow trout Oncorhynchus mykiss and brown trout Salmo trutta acclimated to freshwater or salinities of 9.0‰ or less were exposed to Yersinia ruckeri, the bacterial pathogen that causes enteric redmouth disease (ERM). Both species of fish were kept in the same recirculating systems after bacterial exposure. Rainbow trout mortality was significantly (P < 0.05) different in each salinity: 96.5% in freshwater, 89.5% in water of 1.1‰ salinity, 81.3% in 3.0‰ salinity, and 75.0% in 9.0‰ salinity (model SE = 1.0). All deaths occurred between 3 and 12 d after exposure to Y. ruckeri. Only 2.3% of brown trout in all salinities died, and differences among treatments were not significant. For both fish species, Y. ruckeri was isolated from liver, spleen, and trunk kidney of fish dying during this experiment, and lesions of rainbow trout were consistent with ERM. Yersinia ruckeri was not isolated from brown trout surviving for 21 d after bacterial exposure but was isolated from 3 of 24 surviving rainbow trout; a polymerase chain reaction assay detected the DNA of Y. ruckeri in 3 additional rainbow trout survivors. Neither the lesions of fish with ERM nor the percentage of surviving fish subclinically infected with Y. ruckeri was affected by salinity. Bacterial growth in vitro was not affected by low (≤9.0‰) salinity; however, bacterial adhesion to polystyrene was significantly reduced as salinity increased. Although mortality caused by Y. ruckeri was significantly lower for rainbow trout in water with slightly increased salinity, none of the salinities tested was effective in preventing serious losses caused by this pathogen in recirculating systems.  相似文献   

20.
The myxozoan parasite Tetracapsuloides bryosalmonae is the causative agent of proliferative kidney disease (PKD), a highly damaging disease of cultured salmonid fish. Within this study, phylactolaemate bryozoans were collected from a river known to be endemic for PKD and subsequently cultured in the laboratory. Sequential developmental stages of T. bryosalmonae were studied by light microscopy within the living bryozoan colonies, allowing the identification of stages attached to host peritoneum, consistent with previous molecular evidence of cryptic stages. Infection resulted in the production of large numbers of spores, which were released from the bryozoans. Experimental exposure of rainbow trout (Oncorhynchus mykiss) to medium in which infected bryozoans were cultured resulted in clinical PKD. Rainbow trout were exposed to known numbers of T. bryosalmonae spores collected by micromanipulation, which had been released from mature spore sacs within colonies of the bryozoan Fredericella sultana. Exposure to one spore was sufficient to lead to development of PKD. These findings indicate that small numbers of bryozoans are capable of releasing sufficient spores to infect large numbers of fish, having implications for future control methods for PKD in salmonid farming.  相似文献   

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