Biomedical subjects

C Székely

Publications and source records attributed to C Székely.

At least 19 recordsLinked to original sources

PubMed2006

Myxozoan pathogens in cultured Malaysian fishes. I. Myxozoan infections of the sutchi catfish Pangasius hypophthalmus in freshwater cage cultures.

Cage-cultured sutchi catfish Pangasius hypophthalmus (Sauvage, 1878), a favourite food fish in Southeast Asia, proved to be infected by 6 myxozoan species. Three species belonged to the genus Hennegoides (H. berlandi, H. malayensis, and H. pangasii), 1 to Henneguya (H. shariffi) and 2 to Myxobolus (M. baskai, and M. pangasii). Five myxozoans infected the gills and 1 was found on the spleen. Myxozoans infecting the gills were characterised by a specific site selection. H. shariffi sp. n. and H. berlandi sp. n. formed plasmodia in the multi-layered epithelium of the gill filaments. Of the 2 vascular species H. pangasii sp. n. developed in the gill arteries, while M. baskai sp. n. infected the capillary network of the gill lamellae. Plasmodia of H. malayensis sp. n. were found inside the cartilaginous gill rays of the filaments. Large plasmodia of M. pangasii sp. n. were located in a groove of the spleen but they affected only the serosa layer covering the spleen.

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PubMed2006

Myxozoan pathogens in cultured Malaysian fishes. II. Myxozoan infections of redtail catfish Hemibagrus nemurus in freshwater cage cultures.

Cage-cultured Asian redtail catfish Hemibagrus nemurus (Valenciennes, 1840), a popular food fish in Southeast Asia, proved to be infected by 3 myxozoan species. All the 3 species belonged to the genus Henneguya: 2 were identified as H. mystusia Sarkar, 1985 and H. hemibagri Tchang et Ma, 1993, while the other was described as H. basifilamentalis sp. n. All plasmodia were found in the gills and were characterised by a specific site selection. H. mystusia formed plasmodia in the multi-layered epithelium between the gill lamellae and in the non-lamellar edge of the gill filaments, while H. hemibagri developed in the capillary network of the lamellae. H. basifilamentalis sp. n. had large oval plasmodia located deep among the filaments just above the gill arch.

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PubMed2004

Comparative study of X-ray computerised tomography and conventional X-ray methods in diagnosis of swimbladder infection in eels caused by Anguillicola crassus.

To date, swimbladder lesions due to Anguillicola crassus infection of the European eel Anguilla anguilla have so far been studied only by conventional X-ray methods. This is the first study to report the use of computerised tomography (CT) for studying lesions induced by anguillicolosis. Of 50 eels caught by electrofishery from Lake Balaton, Hungary, in autumn 2002 and pre-selected by a conventional X-ray method, 22 specimens were examined with a Siemens Somatom Plus S40 spiral CT scanner. Tomograms, radiographs and photographs of 5 of these, showing anguillicolosis-induced swimbladder lesions of varying severity, are presented. Computerised tomograms provide information on the inner structure, air content and wall thickness of the swimbladder as well as on the number of worms it contains. When the swimbladder is not severely affected or not completely filled with worms, computerised tomography provides adequate data on the shape of the swimbladder, thickness of the swimbladder wall and the location of worms in the lumen. However, in more severe cases, i.e. when the swimbladder is tightly packed with worms or contains no air as a result of wall-thickening, this method fails to determine the number and location of helminths or the thickness of the swimbladder wall.

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PubMed2002

Comparative ultrastructure of the actinosporean stages of Myxobolus bramae and M. pseudodispar (Myxozoa).

The ultrastructrure of triactinospores and other developmental stages obtained after the experimental infection of the oligochaete Tubifex tubifex with myxospores of Myxobolus bramae and Myxobolus pseudodispar was studied. In both cases, pansporocysts harbouring spores and the remnants of polar bodies were found in the gut epithelium of the tubificids. Other stages were also seen in M. pseudodispar. Capsulogenic cells surrounded the apical part of the sporoplasm in M. bramae whereas they were located separately in M. pseudodispar. The sporoplasm of M. bramae was elongated and was filled with numerous infective cells, whereas secondary cells rarely appeared in the sporoplasm of M. pseudodispar, which contained large groups of beta-glycogen granules. Other M. pseudodispar stages included pansporocysts harbouring pregametic or gametic stages, zygotes, or the initial steps of sporogenesis. The presence of first- and second-order polar bodies indicates the existence of meiosis. In the spores of M. pseudodispar, the presence of desmosome-like junctions between the capsulogenic cells, and hemidesmosome-like junctions between the capsulogenic cells and the inner membrane of the valvogenic cells, is remarkable.

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PubMed2001

Radiodiagnostic examination of the swimbladder of some fish species.

Radiodiagnostic methods have not been used previously for studying the anatomy and diseases of the swimbladder of freshwater fish species. In this study, the radiographic anatomy of the swimbladder and species-related differences in swimbladder structure were studied on plain radiographs taken of 12 Hungarian fish species of major economic importance. Changes observed by radiography were also studied by conventional parasitological methods. The radiodiagnostic method reported here appears to be a useful complement to diagnostic examinations that have been based merely on dissection so far. It enables evaluation of the pathological lesions in live condition, without causing damage to the fish.

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PubMed2000

First report on the occurrence of an actinosporean stage (Myxozoa) in oligochaetes from Spanish freshwaters.

Oligochaetes living in the Mijares River close to the Sitjar reservoir, and polychaetes from the brackish and marine waters of a channel flowing into the Mediterranean Sea, both in the province of Castellón (Spain), were examined for the presence of actinosporea. An aurantiactinomyxon was isolated from 60 specimens of the oligochaete Branchiura sowerbyi collected from the river, but no actinospores were isolated from 160 polychaetes collected from the sea channel. The aurantiactinospores were detected by the cell-well plate method. The detected species are not identical with any of the aurantiactinomyxon forms hitherto described in the literature. This is the first report on the occurrence of an actinosporea in Spanish waters.

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PubMed1999

Experimental detection of the actinospores of Myxobolus pseudodispar (Myxosporea: Myxobolidae) in oligochaete alternate hosts.

The development of Myxobolus pseudodispar Gorbunova, 1936, an intracellular myxosporean muscle parasite of the roach Rutilus rutilus L., was studied in experimentally infected oligochaetes. In one experiment, uninfected Tubifex tubifex Müller and Limnodrilus hoffmeisteri (Claparéde) were exposed to mature spores of M. pseudodispar. Triactinomyxon spores developed both in T. tubifex and L. hoffmeisteri specimens. Triactinospores were first released from the oligochaetes 76 d after initial exposure. At that time, pansporocysts containing 8 triactinospores were located in the gut epithelium of experimentally infected oligochaetes, but free actinosporean stages were also found in their gut lumen. Each triactinospore had 3 pyriform polar capsules and an elongated cylindrical sporoplasm with 8 secondary cells. The spore body joined the 3 caudal projections with a relatively long style. One of the 3 caudal projections was shorter than the other two. The total length of the triactinospore was on average 206.5 microns.

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PubMed1999

Myxobolus infection of the gills of common bream (Abramis brama L.) in Lake Balaton and in the Kis-Balaton reservoir, Hungary.

During a five-year survey including studies on the parasite fauna of bream (Abramis brama), four gill-parasitic Myxobolus species (M. bramae, M. hungaricus, M. impressus and M. macrocapsularis) were recorded in a total of 313 breams from Lake Balaton. The commonest species, M. bramae showed a prevalence of 33%, while the other species occurred sporadically. Myxobolus bramae and M. macrocapsularis infected the tips of the gill filaments and caused both intralamellar and interlamellar infection. Intralamellar plasmodia of small size developed in the capillary network of the gill lamellae whereas the much larger interlamellar plasmodia were formed in the arteria afferens. The intralamellar plasmodia of M. hungaricus always infected the basal or central part of the gill filaments. In contrast to the above species developing in the blood vessels, M. impressus proved to be an epithelial parasite, as its plasmodia always developed in the adjacent gill filaments of two opposite haemibranchia, in the stratified epithelium between the respiratory plates, causing changes of the haemibranchium which were well visible even by the naked eye.

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PubMed1999

Relationships among members of the genus Myxobolus (Myxozoa: Bilvalvidae) based on small subunit ribosomal DNA sequences.

Sequences representing approximately 1,700 base pairs of the 18S rRNA gene from 10 different species in the genus Myxobolus were found to group them into 3 clusters that showed little correlation with spore morphology and size or host specificity, criteria currently used for both higher and lower taxonomic placements in the Myxozoa. Of the phenotypic criteria examined, tissue tropism was most correlated with the rRNA groupings observed. Spores of similar size and shape (Myxobolus cerebralis vs. Myxobolus squamalis) were distantly related in some instances, whereas spores with divergent morphology and size were sometimes found to be closely related (M. cerebralis and Myxobolus insidiosus). These initial investigations into the phylogenetic relationships of putative members of the genus Myxobolus clearly indicate the potential limitations of groupings based on size and morphological properties of the spores and host species infected. We propose that 18S rRNA gene sequences, combined with information on tissue tropism, host species infected, and developmental cycles in the fish and alternate host (when and if known) be given greater consideration in taxonomic placements of myxosporeans.

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PubMed1998

Radiodiagnostic method for studying swimbladder inflammation caused by Anguillicola crassus (Nematoda: Dracunculoidea).

The nematode Anguillicola crassus appeared in Europe about 15 yr ago, and has subsequently become recognised as a cause of major pathological lesions in the swimbladder of the European eel Anguilla anguilla. The radiographic method reported in this paper showed be a useful complement to diagnostic methods that have so far been based exclusively on fish dissection. Using this method, the infection of the swimbladder and the severity of its pathological changes can be assessed in a reliable manner without causing damage to the fish. By analysing radiographs of 45 eels from Lake Balaton, 5 stages of swimbladder lesions were distinguished. The method enables the examiner to draw conclusions on the air, worm and exudate content of the swimbladder; however, data on thickening of the swimbladder wall can be obtained only indirectly. The radiograph also provides information on the air and worm content of the pneumatic duct. Results obtained by radiography showed good agreement with dissection findings. Radiographic results are compared with pathological findings obtained from fish dissections separately for each severity grade of infection.

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PubMed1998

Lucionema balatonense gen. et sp. n., a new nematode of a new family Lucionematidae fam. n. (Dracunculoidea) from the swimbladder of the European pikeperch, Stizostedion lucioperca (Pisces).

A new nematode genus and species, Lucionema balatonense gen. et sp. n., is described from the swimbladder of the European pikeperch, Stizostedion lucioperca (L.), from Lake Balaton in Hungary; a new dracunculoid family Lucionematidae fam. n. is established to accommodate it. The hitherto monotypic family Lucionematidae shows affinities with the families Skrjabillanidae and Daniconematidae, differing from them mainly in having simple oesophagus without external oesophageal glands and the vulva situated near the middle of body; from the first family also in the absence of the buccal capsule and the bursa-like caudal alae in the male. The genus Lucionema gen. n. is characterized mainly by the presence of 8 cephalic papillae in two circlets, absence of spicules, presence of the copulatory plate, only 2 pairs of postanal papillae in the male, and by the distal part of the monodelphic uterus forming a posteriorly directed coil. The body length of L. balatonense females is 1074-1782 microns, that of the only available male 770 microns. A key to the families of the Dracunculoidea is presented.

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PubMed1998

Studies on the occurrence of actinosporean stages of fish myxosporeans in a fish farm of Hungary, with the description of triactinomyxon, raabeia, aurantiactinomyxon and neoactinomyxon types.

Actinosporean infection of the oligochaete fauna living in the mud and on the vegetation of fish ponds used for rearing common carp in polyculture was studied during a one-year survey at a fish farm in Hungary, located south of Budapest. Twenty-eight actinospore types were isolated from the oligochaetes Tubifex tubifex, Branchiura a sowerbyi, Limnodrilus hoffmeisteri, Nais elinguis, and Stylaria lacustris collected during the survey, which could be classified into the triactinomyxon, raabeia, aurantiactinomyxon and neoactinomyxon groups. Drawings depicting individual actinospore types are presented on plates and their characteristic dimensions have been summarised in tables. The prevalence and seasonality of actinosporean infections observed in the various oligochaete species have been illustrated graphically. Infection by actinospores showed a pronounced seasonality. In the spring, summer and autumn the prevalence of raabeia infection in Branchiura exceeded 90%, while in the winter it dropped to 42%. A similar phenomenon could be observed for aurantiactinomyxon infection, while neoactinomyxon infection reached its peak in the autumn. In Tubifex, Limnodrilus, Nais and Stylaria species the peak of actinosporean infection occurred, with minor differences, in the spring and summer. Actinosporean infection in the individual Oligochaeta species showed much higher prevalence values than had been reported in the literature, which can be explained by the novelty of the examination technique used. It cannot be decided with absolute certainty which myxosporean developmental stage the different actinospore types described during this survey represent of the species of Myxosporea parasitic in the given ponds. This would require an experimental study for which the data presented here may serve as a basis.

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PubMed1998

Studies on the occurrence of actinosporean stages of myxosporeans in Lake Balaton, Hungary, with the description of triactinomyxon, raabeia and aurantiactinomyxon types.

In the framework of a one-year survey, the actinosporean infection of the oligochaete fauna living in the mud and on the vegetation of Lake Balaton, Hungary was studied. A total of 10 types of actinospores were isolated from the oligochaetes Tubifex tubifex and Limnodrilus hoffmeisteri collected during the survey, which could be classified into the triactinomyxon, raabeia and aurantiactinomyxon groups. The drawings depicting the individual actinospore types are presented on a plate and their characteristic dimensions summarised in tables. The prevalence and seasonality of actinosporean infections observed in the two oligochaete species are illustrated graphically. Infection by actinospores showed pronounced seasonality. In the spring and summer the prevalence of triactinomyxon infection in T. tubifex exceeded 30 and 40%, respectively, while in the autumn it dropped to 6%. In T. tubifex raabeia infection of 3% prevalence was detected only in the summer period. In L. hoffmeisteri the peak of aurantiactinomyxon, raabeia and triactinomyxon infection occurred in the summer with a prevalence of 21, 10 and 8%, respectively. Actinosporean infection in the individual Oligochaeta species showed higher prevalence values than had been reported in the literature, which fact may be explained by the novelty of the examination technique used. Four types of actinospores found in Lake Balaton are identical with the actinospores already described. It cannot be determined with absolute certainty which stages of myxosporeans parasitic in Lake Balaton fishes are identical with the 10 actinospores described.

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PubMed1998

Occurrence of skrjabillanid nematodes in fishes of Hungary and in the intermediate host, Argulus foliaceus L.

Histozoic and coelozoic skrjabillanid-type nematodes belonging to the genera Skrjabillanus, Molnaria, Sinoichthyonema, Esocinema, Daniconema and Lucionema are recorded from the subcutaneous tissues, fins, swimbladder and abdominal cavity of different fish species living in natural waters and fish farms of Hungary. In addition to the nine taxonomically identified parasite species, one Skrjabillanus sp., two Molnaria spp. and three Esocinema spp. were identified to the genus level only. The histozoic larval stages of a Molnaria, Daniconema and Lucionema species each, living in a site different from that of the imagoes, were also detected. The presence of closely not identified first- to third-stage skrjabillanid larvae was demonstrated in 26.3% of the parasitic carp lice (Argulus foliaceus L.) collected from the eight fish species.

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PubMed1997

An unusual location for Ergasilus sieboldi Nordmann (Copepoda, Ergasilidae) on the operculum and base of pectoral fins of the pikeperch (Stizostedion lucioperca L.).

Ergasilus sieboldi infestation of the pikeperch (Stizostedion lucioperca) is extremely common in Lake Balaton. In the summer and autumn, these parasitic copepods have high prevalence and intensity on pikeperch of more than 20 cm body length. Typically, Ergasilus establish themselves in the folds on the external surface of the operculum and on the base of the pectoral fins, and only a small proportion cling to the gill filaments. Infestation is rare and of low intensity in pikeperch of less than 20 cm body length. The Volga pikeperch (Stizostedion volgense) has low-intensity infestation irrespective of age. The lesions caused by copepods present on the operculum are restricted to the epithelium even if infestation is intensive.

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PubMed1997

Attempts to analyse Anguillicola crassus infection and the humoral host response in eels (Anguilla anguilla) of Lake Balaton, Hungary.

Since the introduction of Anguillicola crassus into Europe, anguillicolosis has been a considerable problem in several countries. From 1991, periodical eel mortality occurred in Lake Balaton, Hungary. However, eels with a worm burden of 20 to 50 parasites did not show severe swimbladder lesions, which observation cast doubts on the primary aetiological role of the parasite in the eel kill. In order to study the pathology of the infection, from the spring of 1996 until October of the same year, 51 eels were collected from two regions of Lake Balaton and examined for swimbladder changes. To detect humoral antibodies, an enzyme-linked immunosorbent assay (ELISA) was performed, using cuticular-oesophageal worm antigen. The results of the test show the applicability of the method. However, no direct correlation was found between antibody levels or the intensity of infection and the swimbladder lesions. The low level of specific antibodies and the increasing severity of swimbladder changes in the autumn suggest that parasite-induced immunity is insufficient to prevent reinfection.

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PubMed1996

Experimental studies on the infectivity of Anguillicola crassus third-stage larvae (Nematoda) from paratenic hosts.

The swimbladder parasite Anguillicola crassus Kuwahara, Niimi et Itagaki, 1974 (Nematoda: Dracunculoidea) is a well-known pathogenic parasite of the Japanese and European eels. Numerous studies on the life cycle of the parasite have revealed the involvement of a copepod or an ostracod intermediate host and a fish paratenic host, in which the third-stage larvae (L3) infective to the eel develop. The present study comprised infection experiments with the larvae of A. crassus. These experiments can be divided into three groups: (1) experimental reproduction of the parasite's life cycle via copepod intermediate hosts and fish paratenic hosts, (2) infection of another potential paratenic host with third-stage larvae of A: crassus collected from a paratenic host; (3) study of the ability of larvae damaged by paratenic hosts to infect the final host, the eel. Infection experiments have revealed that larvae which are still viable but have become encapsulated as a result of the host reaction mounted against them by cyprinid paratenic hosts (bleak, Alburnus alburnus) have lost their ability to infect the final host, the eel. At the same time, experimental infection of the eel with larvae derived from other paratenic fish hosts (river goby, Neogobius fluviatilis; ruffe, Gymnocephalus cernua) showing no or only weak host reaction proved to be successful.

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PubMed1995

Dynamics of Anguillicola crassus (Nematoda: Dracunculoidea) larval infection in paratenic host fishes of Lake Balaton, Hungary.

Anguillicola crassus, a nematode parasitizing the swimbladder of the European eel (Anguilla anguilla) caused substantial mortality among eels in Lake Balaton in the years 1991 and 1992. Parallel to a 3-year study of the infection dynamics of eels, Anguillicola larval infection of paratenic host fishes was also surveyed in the lake between 1991 and 1993. During that study, a total of 1,382 specimens of 22 paratenic host fish species were processed. The results showed that anguillicolosis had become a parasitosis widespread throughout the lake, and larval infection could be detected in practically all paratenic hosts examined. The prevalence and intensity values recorded in the paratenic hosts do not completely follow the dynamic change observed during the survey of eel infection. During the study of larval infection in paratenic hosts, only inter-species differences in the prevalence and intensity of infection could be found, rather than the expected course of infection spreading from the West to the East in both space and time. Marked differences existed between paratenic host species in the degree of host reaction to the larvae.

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