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1.
Abstract. Studies on an experimental infection of the stickleback (Gasterosteus aculeatus L.) with the microsporidian Glugea anomala conducted until day 126 post infection confirmed that xenoparasitic formations typical of the intracellular development of this microsporidian were responsible for a marked tissue reaction in the host. After a single oral infection, xenoparasitic formations developed in the subepithelial connective tissue of the glandular part of the stomach. The course of xenoma development was asynchronous. Up to the 'cyst' stage (xenomas filled with mature spores), their growth and development caused a pressure atrophy in the surrounding tissue. Later, the response to the presence of the xenoparasitic formation was the development of a granulomatous inflammatory reaction. Locally, the host responded to the infection by phagocytosis of mature spores by locally derived macrophages. In massive infections, changes occurred in the subepithelial connective tissue of the glandular part of the stomach (often the complete disappearance of tubular glands), which may result in a permanent influence on the function of this organ.  相似文献   

2.
Z Ding  Q Meng  H Liu  S Yuan  F Zhang  M Sun  Y Zhao  M Shen  G Zhou  J Pan  H Xue  W Wang 《Journal of fish diseases》2016,39(9):1043-1051
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3.
Loma salmonae (Putz et al., 1965) infections were observed in five groups of coho salmon, Oncorhynchus kisutch, reared in seawater net-pens in Washington State, U.S.A. in 1984–1986. Ultrastructural characteristics, size of spores, tissues and host infected, and geographical location identified the microsporidium as Loma salmonae. Preserved spores measured 4.4×2.3 (4–5.6×2–2.4) μm and exhibited 14–17 turns of the polar filament. Infections were evident in the gills of some fish before seawater entry, but few parasites were observed and they caused little tissue damage. Infections observed in fish after transfer to seawater were associated with significant pathological changes in the gills. A mixed inflammatory infiltrate was associated with ruptured microsporidian xenomas within the vessels and interstitium of the primary lamellae. Microsporidian spores were dispersed throughout the lesions and were often seen inside phagocytes. The parasite was also observed in the heart, spleen, kidney and pseudobranchs; however, the inflammatory lesions were common only in the heart.

Monthly examination of fish after transfer to seawater showed peak prevalences (33–65%) of gill infections during the summer. Although moribund fish were often infected with other pathogens, the high prevalence of L. salmonae infections and the severity of the lesions it caused, suggested that this parasite significantly contributed to the recurrent summer mortalities observed at this net-pen site.  相似文献   


4.
The sea louse, Lepeophtheirus salmonis, is an obligate ectoparasitic copepod that lives on the external surface of salmonid fish. It is the most common ectoparasite of marine cage-reared salmonids, causing major economic loss to the aquaculture industry. During a sea louse monitoring programme, samples of L. salmonis were found to harbour an unreported microsporidian parasite. The microsporidian was observed in pre-adult and adult stages of both male and female copepods, with a prevalence of up to 5%. Unfixed spores were slightly pyriform in shape measuring 2.34 microm by 1.83 microm (+/- 0.01 microm) and were not observed to be enclosed by a sporophorous vesicle. The microsporidian infection was observed in all areas of the copepods' body, xenoma-like cysts forming directly under the cuticle in the epidermal tissue layer. In the present study, rDNA (530f-580r) sequence data gathered from the unidentified microsporidian parasite isolated from infected sea lice were compared with equivalents available in the databases in an attempt to identify its systematic position. The microsporidian was found to group within the phylogenetic clade containing the family Enterocytozoonidae, being most similar to members of the intranuclear genus Nucleospora. This is the first report of a hyperparasitic microsporidian infecting a caligid copepod.  相似文献   

5.
Enterospora nucleophila is an intranuclear microsporidian responsible for emaciative microsporidiosis of gilthead sea bream (GSB). Its minute size and cryptic nature make it easily misdiagnosed. An in situ hybridization (ISH) technique based on antisense oligonucleotide probes specific for the parasite was developed and used in clinically infected GSB in combination with calcofluor white stain (CW) and other histopathological techniques. The ISH method was found to label very conspicuously the cells containing parasite stages, with the signal concentrating in merogonial and sporogonial plasmodia within the infected cell nuclei. Comparison with CW demonstrated limited ISH signal in cells containing mature spores, which was attributed mostly to the scarcity of probe targets present in these stages. Although spores were detected in other organs of the digestive system as well as in the peripheral blood, proliferative stages or parasite reservoirs were not found in this work outside the intestines. The study demonstrated a frequent disassociation between the presence of abundant spores and the intensity of the infections as determined by the parasite activity. The ISH allows confirmatory diagnosis of GSB microsporidiosis and estimation of infection intensity and will be a valuable tool for a more precise determination of parasite dissemination pathways and pathogeny mechanisms.  相似文献   

6.
Anglerfish from the genus Lophius are a globally important commercial fishery. The microsporidian Spraguea infects the nervous system of these fish resulting in the formation of large, visible parasitic xenomas. Lophius litulon from Japan were investigated to evaluate the intensity and distribution of Spraguea xenomas throughout the nervous system and to assess pathogenicity to the host and possible transmission routes of the parasite. Spraguea infections in L. litulon had a high prevalence; all fish over 403 mm in standard length being infected, with larger fish usually more heavily infected than smaller fish. Seventy percent of all fish examined had some gross visible sign of infection. The initial site of development is the supramedullary cells on the dorsal surface of the medulla oblongata, where all infected fish have parasitic xenomas. As the disease progresses, a number of secondary sites typically become infected such as the spinal, trigeminal and vagus nerves. Fish with infection in the vagus nerve bundles often have simultaneous sites of infection, in particular the spinal nerves and along the ventral nerve towards the urinary bladder. Advanced vagus nerve infections sometimes form xenomas adjacent to kidney tissue. Spraguea DNA was amplified from the contents of the urinary bladders of two fish, suggesting that microsporidian spores may be excreted in the urine. We conclude that supramedullary cells on the hindbrain are the primary site of infection, which is probably initiated at the cutaneous mucous glands where supramedullary cells are known to extend their peripheral axons. The prevalence of Spraguea infections in L. litulon was very high, and infections often extremely heavy; however, no associated pathogenicity was observed, and heavily infected fish were otherwise normal.  相似文献   

7.
Abstract The microsporidian parasite Thelohania sp. was present in a population of Cherax quadriearinatus in the Mitchell River, north Queensland. An infection rate of 7--8% was recorded for the population sampled. Cohabitation, passage of spores through fish, ingestion of spores and injection of blood from an infected individual failed to elicit infection in laboratory held animals. Injection of spores elicited a host responseconsisting of encapsulation and melanization of spores. Further studies are necessary to clarify the taxonomic position and mode of transmission of this parasite.  相似文献   

8.
Abstract. A normally free-living hymenostomatid ciliate was found to be the cause of heavy infections of gills, viscera and body muscle in Atlantic and Pacific marine fishes kept in the New York Aquarium. Of special interest is the fact that the parasites, usually with food vacuoles filled with blood cells and cellular debris, caused extensive damage to the body muscle; the other infected organs showed no characteristic tissue reactions. The immediate cause of death is attributed to the exceptional load of the parasite on the gills, thus interfering with normal respiratory function.
The ciliate, isolated from a recent outbreak, is described in detail, and shows many characteristics of Uronema marinum Dujardin, a species that has been reported as free-living in salt water; the form reported here differs from the type and other members included in this species, by the presence of less than three rows of bipolar meridians. This facultative parasite is described in detail and compared with other genera.  相似文献   

9.
舟山地区大棚凡纳滨对虾生长缓慢病因的调查分析   总被引：1，自引：0，他引：1  
2013年以来,浙江省舟山地区大棚养殖的凡纳滨对虾(Penaeus vannamei)普遍出现生长缓慢、养殖成功率低的现象。为了查明该原因,本研究采用分子生物学和组织病理学等方法对引起对虾生长缓慢的病因开展了调查分析。结果显示,采集的270份病虾样本中,对虾肝肠胞虫(Enterocytozoon hepatopenaei,EHP)PCR阳性检出率高达85.19%,传染性皮下及造血器官坏死病毒(infectious hypodermal and hematopoietic necrosis virus,IHHNV)检出率为0;所有采集的病虾样本中也未分离到常见的致病菌;54份正常的对虾样本中EHP和IHHNV均未检出。将病虾PCR扩增产物进行序列测定和比对分析,结果获得的序列片段与Gen Bank中已有EHP相关序列相似性高达99.55%;病虾的肝胰腺组织病理切片观察显示,在虾肝胰腺组织中可观察到处于各个生长发育阶段的EHP。通过上述研究,初步认为EHP是引起舟山地区大棚养殖对虾生长缓慢的一个重要病原。  相似文献   

10.
An outbreak of a disease characterized by a peculiar spiral movement in farmed greater amberjack, Seriola dumerili (Risso), occurred in Kagoshima Prefecture, Japan, in May 2008, immediately after importing the fish from China. Although neither bacteria nor viruses were detected in routine diagnostic tests, histopathological observations of the affected fish revealed severe inflammation in the tegmentum of the brain including the medulla oblongata and the anterior part of the spinal cord. In addition, a microsporidian parasite was observed in the nerve cell bodies or axons in the inflamed tissues. We identified a microsporidian small subunit rRNA gene (SSU rDNA) from the lesion, and the sequence showed 96.1% identity with that of Spraguea lophii. Subsequent in situ hybridization using probes presumably specific to the SSU rRNA confirmed that the parasite observed in histopathology harboured the identified SSU rRNA. Apparently degenerated microsporidian cells or spores were also frequently observed in tissue sections. Thus, the disease was most probably caused by the infection of a hitherto unknown microsporidian parasite that has a genetic affinity to the genus Spraguea, in the central nervous system of the amberjack.  相似文献   

11.
Abstract. Sphaerospora angulata Fujita, 1912, has been identified as a frequent renal parasite of cultured carp populations in Hungary. Its prevalence ranged from 10 to 50% in the pond farms surveyed. The youngest carp infected were 21/2–3 months old. Infections were not common in one-summer fish and tended to become less frequent with increasing age of the host.
The developing stages of S. angulata are found in the contorted tubules of the trunk-kidney but never invade the parenchymal tissue of the trunk or head-kidneys. The pansporoblasts developing in the wide proximal segment of the renal tubules, and the spores arising from the pansporoblasts are typically coelozoic parasites, for they apparently do not damage the tubular lining epithelium, nor its brush border. The main adverse effect of S. angulata is probably depression of resistance owing partly to deprivation of the host of nutrients secreted by the glomeruli and partly to mechanical obstruction of the distal tubular segments.  相似文献   

12.
The life cycle of the histozoic myxozoan parasite Henneguya nuesslini was investigated in two salmonid host species. Naive brown trout, Salmo trutta, and brook trout, Salvelinus fontinalis, were experimentally infected in two trials by triactinomyxon type actinospores from naturally infected Tubifex tubifex. In exposed common carp, Cyprinus carpio, no myxospore production was detected. The parasite formed cysts with mature myxospores in the connective tissue of the fish 102 days post-exposure. The morphology of both actinosporean and myxosporean stages was described by light microscopy and a 1417-bp fragment of the 18S rDNA gene was sequenced. Sequence analysis confirmed the absolute congruence of the two developmental stages and assisted in determining species identity. Host range, tissue specificity and myxospore measurements provided sufficiently distinctive features to confirm species validity and were thus crucial for identification. The triactinomyxon spores had 16 secondary germ cells, unique dimensions, a very opaque sporoplasm matrix and three conspicuously protruding, pyriform polar capsules. This is the first record of a Henneguya sp. life cycle with a triactinomyxon-type actinospore, which suggests a close relationship with the Myxobolus group and a polyphyletic origin of the genus Henneguya.  相似文献   

13.
Abstract. A mature microsporidian infection of the skeletal muscles of Norway pout, Trisopterus esmarkii Nilsson, is described. Infected fish had noticeable liquefaction of the muscle. The white foci of infection contained packed microsporidian spores, and the surrounding infected muscle fibres were degenerate. The host response involved invasion by phagocytic cells and encapsulation by fibroblasts, forming large granulomas. Macrophages, 17–20 μm in diameter, were actively ingesting the spores and typically had a foamy cytoplasm. Some had formed Langhans-type giant cells, 35 μm in diameter, with peripherally arranged nuclei. Sporulation was complete and appeared to have occurred within sporo- phorous vacuoles in which numerous spores were formed. Individual spores measured 2·8 × 1·5 μm and were characterized by irregular electron dense areas, a short polar filament with four coils and a large posterior vacuole with three inclusions.  相似文献   

14.
Lernaeocera branchialis, a copepod crustacean parasite of gadoids, represents a potential threat to both wild and farmed cod, Gadus morhua. The pathological changes associated with the early stages of experimental infection have previously been reported in detail, and this article describes the lesions associated with later chronic stages of experimental infection. Chronic infection is characterised by extravascular granuloma formation and proliferation of fibrovascular tissue around intact and fragmented, degenerate parasites within both the gill arch and cardiac region. The majority of parasite granulomas are located within connective tissues of the gill arch or pericardium; however, low numbers are present within the wall of large vessels. The intraluminal parasites and thrombi of early stage infection are largely absent in these later lesions. We propose that organisation and incorporation of the parasite thrombus into the vessel wall with subsequent granuloma formation and extrusion into the surrounding connective tissue leads to the elimination of the parasite from the vascular system. Thus, rather than being a negative consequence of infection thrombosis is protective, allowing the host to survive the substantial initial vascular insult.  相似文献   

15.
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16.
Abstract. The possibility of oral transmission of the pleistophorid microsporidian parasite Vavraia parastacida Langdon from marron, Cherax tenuimanus (Smith), was investigated by feeding infected marron and yabby, Cherax albidus Clark, muscle to juvenile marron and yabbies. Infections were established in a proportion of marron and yabbies with tissue from both crayfish, and both mounted a vigorous haemocytic response which failed to arrest progress of the disease. The disease appeared to progress more rapidly in the yabbies, in which no natural cases have been found. It would appear inadvisable to mix marron and yabbies on crayfish farms unless the marron are first demonstrated to be free of the parasite. As an intermediate host is not essential to transmission, which can occur through cannibalism, the exclusion of possible vectors will not control vavraiasis on crayfish farms, It remains possible that an alternate life cycle involving intermediate or transport hosts also takes place.  相似文献   

17.
Vertebrates mount a series of immune reactions when invaded by helminths but antihelmintic immune strategies allow, in many cases, the first invaders of the non-immune host to survive for prolonged periods, whereas subsequent larval invaders of the same parasite species face increased host resistance and thereby decreased colonization success. This concomitant immunity may represent a trade-off between adverse side effects (associated with killing of large helminths in the host tissue) and the need for future protection against invasion. Encapsulation and isolation of large live endoparasitic larvae may be associated with less pathology compared to coping with excess dead parasite tissue in host organs. Likewise, live adult nematodes may be accepted in tissues at a certain activity level for the same reasons. Various host cell receptors bind helminth molecules after which signal-transducing events lead to mobilization of specific reaction patterns depending on the combination of receptors and ligands involved. Both innate and adaptive responses (humoral and cellular) are prominent actors, but skewing of the Th1 lymphocyte response towards a Th2 type is a characteristic element of antihelminthic responses in mammalian hosts. Similar patterns may be expected also to occur in at least some fish species, such as salmonids, producing relevant cytokines, MHCII and CD4+ cells required for these lymphocyte subpopulations. Atlantic cod, Gadus morhua L., is without these immunological elements that indicate that alternative reaction pathways exist in at least some fish groups. Recent achievements within teleost immunology have made it possible to track these host responses in fish and the present work outlines the main immune reactions in fish against helminths and suggests three experimental fish models for exploration of these immune pathways in fish infected with nematodes.  相似文献   

18.
Abstract. Cyprinid fish from the Lergue and Lez rivers in Herault, southern France, were found to be parasitized by the microsporidian Pleistophora mirandellae Vaney & Conte, 1901. The parasite was found only in the gonads, forming cysts in the connective tissue between the seminiferous tubules of testes or occurring in the oocytes of the ovaries. Two types of uninuclear spores are produced. The synonomy of microsporidia parasitizing the gonads of cyprinid fish is discussed.  相似文献   

19.
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   

20.
Bullheads, Cottus gobio, with macroscopic external cysts on the skin and fins measuring up to 3 mm in diameter were detected in the River Allen and its tributaries in southern England between 1992 and 1998. The prevalence of these cysts was up to 50% at some sites. Examination of cyst contents revealed the presence of numerous spores, typical of the genus Dermocystidium, measuring 8 microm in diameter. The parasite developed within well-defined cysts, which were located in the hypodermal connective tissues of the host. No cysts were present on the fins of any of the fish examined. Histological examination revealed a cyst wall consisting of an inner layer of dense eosinophilic material similar to that reported for Dermocystidium spp. forming coenocytic hyphae. No evidence was found of systemic infection or hyphal formation. Spores contained a prominent refractile body, which gave a weakly positive reaction for polysaccharides with the periodic-acid Schiff reaction and was positively stained with acidic dyes. Several examples of ruptured cysts were seen in histological sections and in some of these cases the host epithelial layer was breached, allowing release of the spores to the environment. Morphological features of, and host response towards, the Dermocystidium sp. in bullheads are compared with similar infections in salmonids and other freshwater fish species.  相似文献   

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