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1.
Abstract. Serologic relatedness of the two life stages of the salmonid whirling disease parasite Myxosoma cerebralis Hofer, 1903 — myxosporean spores from fish cartilage and actinosporean triactinomyxon spores from aquatic tubificids — were investigated. When the direct fluorescent antibody technique was used, anti-triactinomyxon and anti- M. cerebralis rabbit sera conjugated with fluorescein isothiocyanate cross-reacted with the respective heterologous life stage. Both stages showed similar locations of specific fluorescence with conjugates of either homologous or heterologous serum. Thus, serology supports the relatedness of the myxosporean M. cerebralis and the actinosporean triactinomyxon stages.  相似文献   

2.
Myxozoa (phylum Cnidaria) are a diverse group of metazoan parasites that predominately infect fish. Little is known regarding the composition and physiology of their myxospore life stage. The objective of this work was to investigate the composition of myxospores and extrasporogonic stages of nine myxozoan species infecting various teleost fish using histochemical staining techniques. Thirty histochemical stains were applied to formalin-fixed, paraffin-embedded tissues processed routinely for light microscopic evaluation. The polar capsules were the most consistent stain target across the taxa examined. Polar capsule staining with Alizarin red, von Kossa and methyl green-pyronin suggests the presence of intracapsular calcium and phosphate, which may contribute to polar filament discharge or pathogenesis of host invasion. The shell valves and suture lines of most myxozoans were stained with Luna and phosphotungstic acid haematoxylin stains, consistent with the presence of chitin and microfibrils, respectively. Vacuoles were consistently highlighted by diastase-susceptible periodic acid-Schiff and Grocott's methenamine silver staining, indicating glycogen. Other histochemical stains exhibited inconsistent staining across the taxa, suggesting differences in myxospore composition potentially reflective of physiologic variations and tissue tropisms. This work provides some information on conserved features and taxa-associated composition of myxospores and lends insight into myxozoan physiology and host–parasite interactions.  相似文献   

3.
Caligus rogercresseyi, [Contrib. Zool. 69 (2000) 137] is the only caligid known to affect the salmon industry in Southern Chile. Economic losses due to reduced fish quality, cost of chemical treatment and outbreaks of other diseases such as the Piscirickettsiosis occur. The life cycle of C. rogercresseyi is described in rainbow trout reared in seawater tanks from observations made under natural conditions of light and temperature between January 1997 and April 1998. Fish were infected with laboratory-cultured larvae obtained from ovigerous females. Rainbow trout were periodically slaughtered for parasite collection and identification. C. rogercresseyi life cycle includes the following stages: two nauplius, one copepodid, four chalimus and the adult. No preadult stage was observed. Timing of the different stages of development was directly dependent on water temperature. The maturation of the eggs or the time for a complete life cycle took place at 45 days in July at 10.3 °C, 31–32 days in April at 12.4 and 12.8 °C, respectively, and at 26 days in November at 15.2 °C. In January, at 16.7 °C, only the appearance of first eggs were observed at 18 days. A simple degree–day (dd) model is proposed for each developmental stage between 4 and 17 °C, where the development rate is a linear function of the average temperature of water. Using this degree–day model, the proportion of fourth stage chalimus was maximum at 172 dd of effective temperature, adult males at 193 degree–days, adult females at 208 dd. The minimum temperature threshold is at 4.2 °C where there is no development of the parasite. The appearance of first eggs occurred at 231 dd and the first pigmented eggs at 277 dd. The temperature-independent degree–days value allowed to predict the timing of C. rogercresseyi life cycle at any temperature within the evaluated range.  相似文献   

4.
This study compared and contrasted the fate of the microsporidian Loma salmonae , a branchial pathogen of salmonids of the genus Oncorhynchus , upon exposure of (1) naive susceptible rainbow trout (RT) O. mykiss , (2) naive RT passively immunized with sera from RT previously exposed to L. salmonae , (3) previously exposed and resistant RT and (4) two species believed to be innately resistant to the parasite, Atlantic salmon (AS) Salmo salar and brook trout (BT) Salvelinus fontinalis . The fish were infected per os with viable L. salmonae spores. The infection was followed in the fish by detection of parasite DNA by polymerase chain reaction (PCR) at several times post-infection. Spore germination and intestinal invasion by the parasite occurred in all groups of fish. In the susceptible RT, parasite DNA was detected in the heart by day 3 post-exposure (PE), followed by the gill at 2 weeks PE, whereas visible xenoparasitic complexes (xenomas) were detected by week 4 PE. In the passively immunized RT, the parasite's fate was similar to that of controls, however, its arrival in the heart was delayed by 1 week. A delay was also detected in RT which had been previously exposed to L. salmonae and then recovered from disease. In these resistant fish, the parasite was able to reach the heart by week 3 PE, however, it failed to reach the gill and form xenomas. In AS and BT, the parasite reached the heart and gills quickly, where it remained for 2 weeks before being cleared; xenomas never formed. We speculate that failure to complete the life cycle in AS, BT and resistant fish might be because of interference by the immune system in the development of the parasite, resulting in the absence of disease in these fish.  相似文献   

5.
Abstract. In an investigation of the occurrence of proliferative kidney disease (PKD) in freshwater fish other than rainbow trout, 18 species of wild fish and seven species of fish raised in cultivation wore sampled from waters where the disease occurred annually in rainbow trout, Oncorhynchus mykiss (Richardson). Results revealed that certain wild stocks of brown trout. Salmo trutta L., grayling, Thymallus thymallus L., and pike, Esox lucius L., were infected with PKD, as were cultivated Atlantic salmon, Salmo salar L., parr, brown trout and char, Salvelinus alpinus (L.). Microscopical examination revealed the presence of the PKX cell in these species and also intraluminal protozoa possibly related to the PKX cell, which were not found in the rainbow trout. Other species of freshwater fish had myxosporidan infections but, unlike PKD infection, there was little host/parasite tissue response. The PKX cell as a myxosporidan stage is discussed and the presence of the disease in wild fish is reported.  相似文献   

6.
Abstract. Sporulated plasmodia of Henneguya sp. infected the gill filaments, interhemibranch septum, gut and other microhabitats of Acanthopagrus australis in Moreton Bay, southern Queensland, whereas Myxobolus sp. infected only the gut. There was usually no inflammatory response, but some plasmodia in the gill filaments were associated with a granulomatous, predominantly lymphoid, response that was not determined by either parasite maturity, or sex and size of fish or season. There was a microhabitat shift in branchial Henneguya infection from predominantly gill filament in juvenile bream to gill septum in older fish. The highest prevalences of Henneguya were in the southern part of Moreton Bay, but trends in seasonal infection and prevalences in relation to size and sex of fish were similar in the western and southern parts of the bay. This suggested a widespread distribution of the putative annelid alternate host in Moreton Bay, with highest densities in the southern part. Myxobolus infection was most prevalent in young male fish at the winter spawning grounds on eastern surf bars.  相似文献   

7.
Abstract. The tissue response of Salmo gairdneri Richardson, against the myxosporean parasite. Ceratomyxa shasta (Noble), was investigated using histological techniques, scanning electron microscopy and immunological methods. The progress of infection in C. shasta -susceptible and resistant steelhead and rainbow trout was examined by standard histological techniques and by indirect fluorescent antibody methods using monoclonal antibodies directed against C. shasta antigens. Trophozoite stages were first observed in the posterior intestine and there was indication that resistance was due to the inability of the parasite to penetrate this tissue rather than to an inflammatory response. Examination of a severely infected intestine by scanning electron microscopy showed extensive destruction of the mucosal folds of the posterior intestine. Western blotting and indirect fluorescent antibody techniques were used to investigate the immunological component of the host response. No antibodies specific for C. shasta were detected by either method.  相似文献   

8.
Glycans and sugar-binding molecules (lectins) form an interactive recognition system, which may enable parasitic organisms to adhere to host cells and migrate into target tissues. The aim of the present study was to analyse surface-associated glycans in the developmental stages of Myxobolus cerebralis (Hofer), the causative agent of whirling disease. A panel of biotin-labelled plant lectins was used to detect a broad spectrum of glycan motifs with high specificity. Binding sites were detected histochemically in the tissue sections of infected rainbow trout, Oncorhynchus mykiss (Walbaum), and infected Tubifex tubifex (Müller), and were characterized by light, fluorescence and transmission electron microscopy. With mannose-specific lectins [Lens culinaris agglutinin, Pisum sativum agglutinin, Canavalia ensiformis agglutinin (LCA, PSA, CanA)] mannose-containing glycans were detected in all the developmental stages and host tissues. No binding sites for galactose-specific lectins were present in M. cerebralis spores but reactivity with host tissues occurred. Diversity in glycans was detected by N-acetyl-D-galactosamine-specific lectins in sporoplasm cells of M. cerebralis and triactinomyxon spores. In the group of lectins with monosaccharide-specificity for N-acetyl-D-glucosamine (GlcNAc), the reactivity of Datura stramonium agglutinin (DSA), Lycopersicon esculentum agglutinin (LEA) and Solanum tuberosum agglutinin (STA) was restricted to polar capsules whereas Griffonia simplicifolia agglutinin II (GSA II) also bound to sporoplasm cells of stages in the fish host but not in those present in infected T. tubifex. Moreover, Triticum vulgaris (wheat germ) agglutinin (WGA) and succinylated WGA indicated the presence of N-acetyl-D-glucosamine polymers in polar capsules. No specificity for spores was observed concerning 'bisected'N-glycans and no reactivity in parasitic stages was observed with the fucose-binding lectin Ulex europaeus agglutinin (UEA) I, Sambucus nigra agglutinin (SNA) (specific for alpha2,6-sialylated glycans) and Maackia amurensis agglutinin (MAAI) (specific for alpha2,3-sialylated glycans). Arachis hypogaea (peanut) agglutinin (PNA), Erythrina cristagalli agglutinin (ECA), GSA I, Sophora japonica agglutinin (SJA), Dolichos biflorus agglutinin (DBA) and GSA II detected reactive sites solely confined to the developmental stages of M. cerebralis and were not reactive in the fish host. These parasite-specific glycans may play a role in the adhesion process of the parasite to fish epidermis prior to infection, but may provide protection to the host by activating the complement system, or stimulating an adaptive immune response as putative antigens.  相似文献   

9.
Abstract. Infestation parameters for the calígíd copepod Lepeophtheirus salmonis (Kroyer) infesting sea trout, Salmo trutta L., were established for a number of locations off the west coast of Ireland during 1990 and 1991. Based on these parameters sites were classified into two groups in 1990 and three in 1991. Median parasitic intensity in these groups was 11·6 and 77 in 1990 and 9·5, 29·5 and 55 in 1991. Fish were parasitized mainly by chalimus stages of the parasite which attached preferentially to the fins. Heaviest infestations were invariably due to chalimus stages and early pre-adult lice and there was a progressive decrease in the correlation between parasitic intensity and the number of each successive stage in the life cycle. This suggested either host or parasite mortality as the parasite matured. Large numbers of lice-infested fish returned prematurely from the sea to estuarine areas at a number of sites. Extensive morphological damage, especially to the fins, was apparent on a proportion of these fish as a result of the infestation. Mortality of heavily infested fish was directly observed.  相似文献   

10.
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11.
Paracartia grani (Copepoda) has been identified as a potential intermediate host in the life cycle of Marteilia   refringens , a paramyxean parasite infecting flat oysters. However, no intermediate host has yet been identified for Marteilia maurini that infects mussels. A better understanding of the life cycle of these two Marteilia types would clarify their taxonomic relationship and hypothesized co-specificity. For this purpose, experimental infections of copepods, P. grani , were performed using naturally infected flat oysters and mussels. Infection patterns were different depending whether copepods were infected from oysters or mussels. M. maurini did not proliferate in copepods while M. refringens rapidly proliferated in infected copepods. Previously unrecognized developmental stages of M. refringens were found during this study.  相似文献   

12.
Abstract. Histopathological studies on natural and experimental infections of nineteen microsporidian species from fishes distinguished two types of tissue reactions.
The first type is characteristic of infections with xenoma-inducing microsporidian species and comprises three successive stages: a weakly reactive stage, a productive stage with the formation of granulomas and a stage of granuloma involution. Following the first stage, tissue reactions are directed towards the isolation of the parasite and result in its complete elimination and host tissue repair. The extent of pathological changes probably depends on the number of parasite cells which initiated the infection.
The second type is represented by Pleistophora species infecting muscles or oocytes. Host tissue reaction is surprisingly slight during the schizogony and sporogony and does not tend to isolate the invaded muscle fibres. A slight lymphocytic infiltration of myosepta indicates the first stage of tissue reaction. The tissue reaction only reaches the productive stage when mature spores completely fill the contents of the infected muscle fibre. A thick wall of fibroblasts may be formed to demarcate the parasite mass as soon as it undergoes necrotic changes. The extent of pathological changes probably depends on the ability of early developmental stages of the parasite to spread the infection within the host.
In both types of tissue reaction, the spores are destroyed by complete digestion within host phagocytic cells.  相似文献   

13.
Temperatures above 20 °C or below 9 °C interrupt the life cycle of the gill intracellular microsporidian parasite Loma salmonae (Microspora) prior to sporogony, inhibiting the production of xenomas. This study intended to characterize this life-cycle failure. Juvenile rainbow trout, Oncorhynchus mykiss (Walbaum), were experimentally infected with L. salmonae spores, and the effect of water temperature on the progress of infection, as determined by polymerase chain reaction, was compared for fish held at water temperatures of 5, 15 and 21 °C. At 15 °C, parasite DNA was first detected in the heart (3 days post-exposure [PE]), and then in the gills and spleen (2 weeks PE). Branchial xenomas developed by week 4 PE. In contrast, at 5 °C, the arrival of the parasite in the heart was delayed until 7 days PE. However, even though parasite DNA was detected in the gills at 7 days PE, xenomas failed to form in the gill, and by week 4 PE, parasite DNA was no longer detected. In fish held at 21 °C, parasite DNA was detected in the heart, gills and spleen by 3 days post-infection, and similar results were observed at 7 days PE. Xenomas also failed to form in these fish and parasite DNA was no longer detected by week 2 PE. Within the range of temperatures tested in this study, spore germination and delivery of their DNA into the host through the intestinal wall was not blocked by temperature. At 5 or 21 °C, migration to the heart and gills occurred, but at aberrant periods of time. The normal life cycle of L. salmonae may depend on the completion of relatively lengthy, but yet unknown, stages of development within the heart, prior to reaching the gill. This development may be adversely affected by temperature, and explain the temperature limits of this parasite.  相似文献   

14.
Abstract. Two monoclonal antibody probes were produced against PK'X' cells. The parasites were partially purified by filtration and centrifugation of kidney tissue from rainbow trout with proliferative kidney disease and used as antigen for immunization of mice. The resulting monoclonal antibodies reacted with PK'X' cell antigens in enzyme-linked immunosorbent assay and immunohistochemistry tests. One antibody (Mab 12) appeared to be specific for PK'X'in kidney tissue, while the other (Mab 18) cross-reacted with host cell antigens in the kidney tubules. These probes are invaluable tools for the investigation of parasite surface antigens and life cycle studies.  相似文献   

15.
The development of Myxobolus bramae Reuss 1906, a myxosporean parasite of the gills of common bream Abramis brama L., was studied in experimentally infected oligochaetes. In five experiments, uninfected Tubifex tubifex (Müller) and Limnodrilus hoffmeisteri Claparéde were exposed to mature myxospores of M. bramae . In four experiments triactinomyxon type actinospores developed in Tubifex specimens but no infection was found in Limnodrilus . Actinospores were released from oligochaetes 70–81 days after initial exposure. At that time pansporocysts containing eight actinospores were located in the gut epithelium of experimental oligochaetes, but free actinosporean stages were also found in their gut lumen. Each actinospore had three pyriform polar capsules and a barrel-shaped sporoplasm with 32 secondary cells. The spore body joined the three caudal projections with a stout style. The total length of the actinospore was 139 μm on the average.  相似文献   

16.
Swimming stamina, measured as time-to-fatigue, was reduced by approximately two-thirds in rainbow trout experimentally infected with Ichthyophonus. Intensity of Ichthyophonus infection was most severe in cardiac muscle but multiple organs were infected to a lesser extent. The mean heart weight of infected fish was 40% greater than that of uninfected fish, the result of parasite biomass, infiltration of immune cells and fibrotic (granuloma) tissue surrounding the parasite. Diminished swimming stamina is hypothesized to be due to cardiac failure resulting from the combination of parasite-damaged heart muscle and low myocardial oxygen supply during sustained aerobic exercise. Loss of stamina in Ichthyophonus-infected salmonids could explain the poor performance previously reported for wild Chinook and sockeye salmon stocks during their spawning migration.  相似文献   

17.
The myxozoan parasite Chloromyxum auratum Hallett, Atkinson, Holt, Banner & Bartholomew, 2006 , was shown experimentally to have a two‐host life cycle which involved a previously undescribed antonactinomyxon actinospore stage. Myxospores obtained from gall bladders of naturally infected feral goldfish, Carassius auratus (L.), were used to infect samples of mixed species of oligochaete worms obtained from the same locality as the fish: Fern Ridge Dam, Oregon, USA. After some 110 days post‐exposure, actinospores were detected from the water above the oligochaetes. The 18S rDNA sequence of these actinospores was identical to the original myxospores. Spore release was sporadic, of low intensity and short duration, which confounded efforts to identify the host oligochaete species and infect naïve fish. This is the first life cycle that incorporates an actinospore of the collective group Antonactinomyxon, and the first life cycle demonstrated in the laboratory for a species of Chloromyxum.  相似文献   

18.
Abstract Freshwater fish in Czechoslovakia were examined for species of the genus Sphaerospora Thélohan, 1892 and for myxosporean life cycle stages in the blood. In addition to perch infected with S. pectinacea Bocharova & Donets, 1974, renal tubules of seven host species harboured thus far unidentified Sphaerospora species. A new species, S. gobionis sp.nov. is described from renal tubules of Gobio gobio. In populations of Gobio gobio, Tinea tinea and Rutilus rutilus harbouring infections with different Sphaerospora species, organisms identified as mobile myxosporean life cycle stages were detected in the blood, where they undergo a proliferative cycle. These organisms were reminiscent of stages in the blood of common carp fingerlings, supposedly identical with Sphaerospora renicola Dyková & Lorn. It is possible that the blood stages found in the three cyprinid hosts represent stages of the life cycle of their respective Sphaerospora species. If this is correct, further studies may show if the presence of proliferative stages in the bloodstream is a character distinctive of the genus Sphaerospora.  相似文献   

19.
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20.
Abstract. Cancer pagurus (Cancridae) from the Atlantic coast of France is parasitized by a new species of microsporida Ameson atlanticum sp. nov. The main stages of the life cycle of the parasite are a monokaryotic and then diplokaryotic meront, tetranucleate (at least) sporont fsporogonial sporont), uninucleate sporoblast and spore. The spore (1.9 × 1.5 μm) possesses 11–12 coils of the polar filament and a lamellar polaroplast. Hairlike appendages are present on the surface of the sporoblastic plasmodium, sporoblast and spore. All stages take place in direct contact with the muscular tissue of the crab. Infection provokes the destruction of 80% of host muscle myofibrils.  相似文献   

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