Evidence of the American Myxobolus dechtiari was introduced along with its host Lepomis gibbosus in Europe: Molecular and histological data

The American pumpkinseed Lepomis gibbosus, was introduced to Europe more than one hundred years ago. Currently it is a common fish in European freshwaters but relatively few specific parasites infect this fish in this new habitat. In Europe only a single species, Myxobolus dechtiari seems to represent the American myxosporean fauna of centrarchid fishes. M. dechtiari was found in both Portugal and Hungary. This species forms plasmodia with elongated shape inside the cartilaginous rays of gill filaments. In the advanced stage of infection, after disruption of plasmodia, small groups of myxospores remain enclosed in the cartilaginous gill rays causing distortions in the filaments. Myxospores were ellipsoidal in frontal view and lemon-shape in sutural, length 12.5 ± 0.46 (12–13.4) μm, width 10 ± 0.37 (9.6–10.4) μm, and thickness 7.4 ± 0.37 (7–8) μm; the polar capsules were pyriform, equal in size, length 5.6 ± 0.21 (5.3–6) μm, width 3.2 ± 0.16 (3–3.6) μm; Seven to eight polar tube coils were arranged perpendicularly to the capsule length. There was a small, round, 0.4 ± 0.1 (0.3–05) (N = 50) intercapsular appendix in the spores. The small subunit ribosomal DNA (ssrDNA) of M. dechtiari differed from other myxozoans sequenced to date. Phylogenetic analysis of the ssrDNA gene sequence placed this species in a clade including actinospores and Myxobolus species: Raabeia type1, Triactinomyxon sp., and Myxobolus osburni infecting the same host fish.

The focus of our study was to prove that the pumpkinseed, a fish originated from North-America introduced one of its myxosporean parasite to Europe. Emphasis was put on to demonstrate the unique feature of this parasite causing infection in the cartilaginous gill rays.

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American pumpkinseed fish were introduced to Europe as an ornamental fish.

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Relatively few specific parasites are reported from the pumpkinseed in Europe.

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The myxosporean Myxobolus dechtiari described originally in Canada infects the introduced host both in Hungary and Portugal.

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SsrDNA sequences of M. dechtiari from pumpkinseed fish is provided.

Histopathological changes on the gills of asp (Aspius aspius) and European catfish (Silurus glanis) caused by Lamproglena pulchella and a Lamproglena sp. (Copepoda: Lernaeidae), respectively

In a parasitology survey of Hungarian fishes, heavy infections of parasitic copepods Lamproglena pulchella and a Lamproglena sp. were found in the gills of the asp and the European catfish, respectively. Individuals of both fish species were emaciated and infected with hundreds of Lamproglena. Copepods located close to the tip of gill filaments and formed a depression at the attachment sites. In histological sections, cell degenerations and local haemorrhages were present adjacent to the maxillipeds and where the maxillary claws pierced the gill tissue. Around maxillae and in the midgut of the Lamproglena, damaged piscine blood cells and remains of the gill tissue were observed. Host reaction was expressed by proliferation of epithelioid cells, increase in both number and size of goblet and mast cells and formation of giant cells.

Malformations of the gill filaments of the ruffe Gymnocephalus cernuus (L.) (Pisces) caused by echinostomatid metacercariae

In parasite surveys of fishes from Lake Balaton and its tributaries in Hungary, infections with metacercariae of a species of the digenean genus Echinochasmus (Trematoda: Echinostomatidae) were found in seven species of fish. In ruffe, Gymnocephalus cernuus, malformations of the gill filaments apparently caused by these infections were observed. These malformations were in the form of bifurcations of the filaments at about their mid-length. At the point where the filaments bifurcate, an Echinochasmus metacercaria was always embedded in the cartilaginous ray of the gill filament. All specimens of the ruffe were found to be infected by these metacercariae, and each ruffe specimen was infected by 30-300 metacercariae. Such a bifurcation was found in all of the ruffe specimens, but, apart from these gill malformations, the metacercariae produced only local changes in the cartilage. In the other six infected fish species, only local signs were observed in the cartilage. Experimental infections of chicks with metacercariae resulted in the finding of the sexual adult (marita) of an unidentified species of Echinochasmus. ITS sequences of the adult and metacercaria corresponded with each other, and also with a cercaria isolated from a gravel snail (Lithoglyphus naticoides), with a 99.5-100% similarity.

Comparison of the Myxobolus fauna of common barbel from Hungary and Iberian barbel from Portugal

We compared Myxobolus infection of common barbel Barbus barbus from the Danube River in Hungary with that in Iberian barbel Luciobarbus bocagei from the Este River in Portugal. In Hungary, we recorded 5 known Myxobolus species (M. branchialis, M. caudatus, M. musculi, M. squamae, and M. tauricus) and described M. branchilateralis sp. n. In Portugal we recorded 6 Myxobolus species (M. branchialis, M. branchilateralis sp. n., M. cutanei, M. musculi, M. pfeifferi, and M. tauricus). Species found in the 2 habitats had similar spore morphology and only slight differences were observed in spore shape or measurements. All species showed a specific tissue tropism and had a definite site selection. M. branchialis was recorded from the lamellae of the gills, large plasmodia of M. branchilateralis sp. n. developed at both sides of hemibranchia, M. squamae infected the scales, plasmodia of M. caudatus infected the scales and the fins, and M. tauricus were found in the fins and pin bones. In the muscle, 3 species, M. musculi, M. pfeifferi and M. tauricus were found; however they were found in distinct locations. Plasmodia of M. musculi developed intracellularly in muscle cells, plasmodia of M. tauricus were found in the dense connective tissue of the pin bones, whereas M. pfeifferi formed plasmodia in the connective tissue of the intramuscular septa. This latter species was often found in the cartilaginous gill arch as well. Comparative morphological and phylogenetic studies, as well as 18S rDNA sequences, revealed differences between the Myxobolus fauna of the 2 barbel species originating from different geographic regions.

National registry of patients with juvenile idiopathic inflammatory myopathies in Hungary—Clinical characteristics and disease course of 44 patients with juvenile dermatomyositis

Idiopathic inflammatory myopathies (IIMs) are systemic autoimmune diseases characterized by chronic muscle inflammation resulting in progressive weakness and frequent involvement of internal organs, mainly the pulmonary, gastrointestinal and cardiac systems which considerably contribute to the morbidity and mortality of the IIMs. Aim of this study was to present clinical characteristics, disease course, frequency of relapses and survival in patients with juvenile dermatomyositis (DM). A national registry of patients with juvenile IIMs was elaborated by the authors in Hungary. We have summarized data of the register according to signs and symptoms, disease course, frequency of relapses and survival of patients with juvenile IIM. Analysis was performed using data of 44 patients with juvenile DM diagnosed between 1976 and 2004 according to Bohan and Peter's criteria. Survival probability was calculated by Kaplan-Meier method. Data of patients with juvenile DM were compared with data of 66 patients with adult DM. The most frequent cutaneous features were facial erythema and heliotrope rash. Extramuscular and extraskeletal manifestations of the disease were more frequent in adult patients. The most common extramuscular feature was arthralgia in both groups of patients with juvenile or adult DM. Cardiac manifestation of the disease was not observed in juvenile patients. Respiratory muscle involvement and interstitial lung disease (ILD) were more frequent among adult DM patients than cardiac manifestation of the myositis. In view of the disease course, the authors found that frequency of polycyclic and monophasic subtypes of the disease were mainly similar. The hazard of relapse was found higher during the first year after the remission. None of the juvenile patients died. Among adult patients four disease-specific deaths occurred. There was no correlation between relapse free survival and initial therapeutic regimen. Many of our patients had polycyclic or chronic disease. As relapses can occur after a prolonged disease-free interval, patients should be followed up for at least 2 years. Although we found favourable survival probability, further investigations are needed to assess functional outcome.

Complete life cycle of Myxobolus rotundus (Myxosporea: Myxobolidae), a gill myxozoan of common bream Abramis brama

The life cycle of Myxobolus rotundus Nemeczek, 1911, a myxosporean parasite of the gills of common bream Abramis brama L., was studied under laboratory conditions. Mature Myxobolus spp. spores from plasmodia in the gills of wild bream were used to infect naïve oligochaete worms in a flow-through system of aquaria. Triactinomyxon-type actinospores were released from the oligochaetes 1 yr later and allowed to continually flow into a tank containing uninfected bream fry. The gills of the fry were checked for development of plasmodia in squash preparations 3 d postexposure, and then at weekly intervals for 8 wk. Tissue samples were fixed at each time point. Developing plasmodia were first observed 17 d post-exposure (Day 17). Mature spores were collected from plasmodia on Day 56 and were added to plastic dishes containing parasite-free Tubifex tubifex oligochaetes. Second-generation actinospores were released from these worms 8 mo post-exposure, and were morphologically identical to first-generation spores. Myxospores obtained from the bream fry were morphologically identical to those identified in wild bream as M. rotundus. Small subunit ribosomal RNA gene sequences obtained from first- and second-generation actinospores and the bream fry myxospores were 100% similar to M. rotundus spores from the original wild fish.

Myxobolus erythrophthalmi sp. n. and Myxobolus shaharomae sp. n. (Myxozoa: Myxobolidae) from the internal organs of rudd, Scardinius erythrophthalmus (L.), and bleak, Alburnus alburnus (L.)

During a survey of myxosporean parasites of cyprinid fish in Hungary, infections caused by unknown Myxobolus spp. were found in the internal organs of rudd, Scardinius erythrophthalmus, and bleak, Alburnus alburnus. Small plasmodia developed in blood vessels of the kidney, liver, testes and intestinal wall. The parasites were studied on the basis of spore morphology and by histological and molecular methods. In most cases, plasmodia were surrounded by host tissue without a host reaction; however, in advanced cases, a connective tissue capsule was seen around plasmodia. Spores collected from the two fish species differed from each other and from the known Myxobolus spp. both in their morphology and 18S rDNA sequences. The two species, described as M. erythrophthalmi sp. n. from rudd and M. shaharomae sp. n. from bleak, are characterized by a specific histotropism to blood vessels, while the organ specificity involves the kidney and for the latter species, most internal organs.

Myxozoan infections in fishes of the Tasik Kenyir Water Reservoir, Terengganu, Malaysia

During a survey on fishes of the Tasik Kenyir Reservoir, Malaysia, 5 new Myxobolus spp. and 2 known Henneguya spp. were found. The specific locations for 2 Myxobolus spp. were the host's muscles, while 2 other Myxobolus spp. were found to develop in the host's kidney and gills, respectively. Of the species developing intracellularly in muscle cells, M. terengganuensis sp. nov. was described from Osteochilus hasselti and M. tasikkenyirensis sp. nov. from Osteochilus vittatus. M. csabai sp. nov. and M. osteochili sp. nov. were isolated from the kidney of Osteochilus hasselti, while M. dykovae sp. nov. was found in the gill lamellae of Barbonymus schwanenfeldii. Henneguya shaharini and Henneguya hemibagri plasmodia were found on the gills of Oxyeleotris marmoratus and Hemibagrus nemurus, respectively. Description of the new and known species was based on morphological characterization of spores, histological findings on locations of plasmodia and DNA sequence data.

Myxozoan pathogens of Malaysian fishes cultured in ponds and net-cages

We describe new myxosporean species from Malaysian fishes cultured in pond farms and net-cages. Myxobolus omari sp. nov. and M. leptobarbi sp. nov. were found in the muscles of Pangasianodon hypophthalmus and Leptobarbus hoevenii, respectively, while plasmodia and spores of Thelohanellus zahrahae sp. nov. and Henneguya daoudi sp. nov. were detected in the gills of Barbonymus gonionotus and Trichogaster trichopterus, respectively. Plasmodia and spores found in these fishes differed from the known myxosporean species in respect of their morphology, tissue tropism and 18S rDNA structure. No major pathological changes were found, but in the future these species might pose a potential threat to more intensified fish culture.

Infection of the heart of the common bream, Abramis brama (L.), with Myxobolus s.l. dogieli (Myxozoa, Myxobolidae)

Myxobolus dogieli Bykhovskaya-Pavlovskaya & Bykhovski, 1940 is regarded as a site specific myxosporean, infecting the heart of cyprinid fish. During a survey of the myxosporean fauna of Lake Balaton fish, heart myxobolosis was found in the common bream, Abramis brama, with heavy infection of the ventricle and the bulbus arteriosus in some infected bream. Developing and mature plasmodia were mostly in the connective tissue of the subepicardium and subendocardium. Plasmodia developing in the subendocardium protruded into the lumen of the heart, while plasmodia developing in the subepicardium protruded over the epicardium forming large sausage-like outgrowths. Plasmodia with mature spores were found in the summer. The shape and size of the spores corresponded to those of the original description. Phylogenetic analysis based on the 18S rDNA sequence of M. dogieli showed that this species fit well in the genus Myxobolus. As no molecular data are available on spores from the type host, common carp, the species studied by us is temporarily designated as Myxobolus s.l. dogieli.

Description of Myxobolus gayerae sp. n. and re-description of M. leuciscini infecting European chub from the Hungarian stretch of the river Danube

Myxobolus gayerae sp. n. and M. leuciscini González-Lanza & Alvarez-Pellitero, 1985 (Myxozoa: Myxobolidae) have been described and re-described from European chub Leuciscus cephalus L. from the Hungarian stretch of the river Danube. The ellipsoidal plasmodia of M. gayerae sp. n. were found in the mucosa of the intestinal wall, whereas the large, elongated plasmodia of M. leuciscini infected the afferent arteries of the gill filaments. The spores of M. gayerae sp. n. are relatively large, slightly oval and almost rectangular in shape. On the basis of spore morphology and 18S rDNA sequences, the most similar species was M. cycloides Gurley, 1893, but the 2 species differed in host and tissue tropism as well as in the size of the spores. The spores of M. leuciscini from L. cephalus, having no intercapsular appendix or occasionally a very small one, showed a high morphological similarity to spores collected from L. cephalus cabeda, Chondrostoma polylepis and Rutilus arcasi in Spain and described as M. leuciscini González-Lanza & Alvarez-Pellitero, 1985.

Myxobolus infections of common carp (Cyprinus carpio) in Syrian fish farms

During a survey on Myxobolus infection of pond-cultured common carp in Syria three Myxobolus spp. were found. Myxobolus dispar infected the gill arteries, forming large elongated plasmodia in the gill filaments. The plasmodia of M basilamellaris were located in the gill arches at the base of the filaments. Elongated filiform plasmodia of M. encephalicus were found in the blood vessels of the brain. Despite the common occurrence of the above parasites, no disease symptoms were observed in the infected fish specimens. This is the first report on myxosporean infection of fish from Syrian waters.

Molecular characterisation of invasive Streptococcus pyogenes isolates from Hungary obtained in 2004 and 2005

Our aim was to characterise by molecular techniques group A streptococci isolated from invasive infections in Hungary in 2004-2005. Twenty-six nonduplicate invasive GAS isolates were selected and examined. The mortality rate proved high (52.3%) for those cases (n = 21) where data were available. Predominant emm types were emm1 (n = 13, 50%) and emm80 (n = 5, 19.2%), but other M types (emm4, emm28, emm66, emm81.1, emm82, emm84) were also identified. Eight different PFGE types were distinguished, and each emm type showed an individual PFGE pattern. Our results show that--similarly to results obtained in several other countries--emm type 1 strains predominate among invasive GAS isolates, and that emm 1 type strains recovered from severe streptococcal infections were associated with the presence of the speA gene. The rate for macrolide resistance proved low: only two isolates showed elevated MICs for erythromycin.

Efficacy of some anticoccidial drugs for treating coccidial enteritis of the common carp caused by Goussia carpelli (Apicomplexa: Eimeriidae)

In this study, nine anticoccidial drugs commonly used in poultry were tested for efficacy for the prevention and treatment of Goussia carpelli (Apicomplexa) infection in common carp (Cyprinus carpio L.). To establish experimental infection with G. carpelli, paratenic host oligochaetes of the genera Tubifex and Limnodrilus were infected with oocysts, and laboratory-cultured parasite-free common carp fingerlings were infected by feeding to them oligochaetes containing sporozoites. The anticoccidial drugs (amprolium, narasin, maduramicin, salinomycin Na, lasalocid Na, diclazuril, robenidine HCl, monensin Na and toltrazuril), mixed in the food of the fish in a dose of 200 mg/kg, were fed for 12 days. Common carp fingerlings fed diclazuril, lasalocid, robenidine HCl or maduramicin and killed on day 14 after exposure were free from infection, while other groups treated with amprolium, toltrazuril, monensin Na, narasin or salinomycin Na harboured oocysts in the mucus and epithelium of the gut.

Comparative morphological and molecular studies on Myxobolus spp. infecting chub from the river Danube, Hungary, and description of M. muellericus sp. n

During a survey on fishes from the River Danube, the occurrence of 8 Myxobolus species (Myxozoa: Myxobolidae) was registered in chub Leuciscus cephalus L. Most species had a specific location within the fish host. M. cycloides was found in the wall of the swimbladder; the branched plasmodia of M. dujardini were located typically in the epithelium of the non-lamellar part of gill filaments; the plasmodia of M. ellipsoides infected fins between 2 fin rays; M. muelleri and Myxobolus sp. 2 formed large elongated plasmodia in the afferent gill artery of filaments, while the round cysts of M. muellericus sp. n. filled the capillary network of the gill lamellae. Intramuscular plasmodia of M. pseudodispar proved to be the most common, although large cysts of Myxobolus sp. 1 were also frequently found in the intestinal wall. Despite similarities of some species in spore morphology, 18S rDNA sequences showed clear differences between the species examined.

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.

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.

The role of copepods (Cyclops spp.) in eliminating the actinospore stages of fish-parasitic myxozoans

The actinospore consumption of copepods (Cyclops spp.) was demonstrated by laboratory observations. It was observed that in experimental dishes the number of actinospores floating in the water decreased, or such actinospores were completely eliminated, in the presence of copepods. The ingestion of actinospores by copepods and their further fate were monitored by fluorescent staining and by conventional histological techniques. The actinospores were observed to have got caught on the filters of Cyclops spp. Two and a half hours after the copepods had been placed into water containing actinospores, their digestive tract was found to contain spores that had extruded their filaments from the polar capsules. After copepods having ingested the actinospores of the species Myxobolus pseudodispar had been fed to roaches, no muscle infection developed in the fish host. It is likely that Cyclops spp. can filter out actinospores floating in the water also from natural waters, thus decreasing the chance of development of myxosporean infections.

Immunostaining of spores and plasmodia of disparate myxozoan genera with comments on the properties of the sporular mucus envelope

Species of the phylum Myxozoa are common parasites of fish and can cause severe losses in cultured species. Although a number of myxozoan life-cycles have now been elucidated, little is known about the biology of these organisms in the fish host. Monoclonal antibody B4 raised to the myxozoanTetracapsuloides bryosalmonaehas been previously noted to react with a number of species infecting fish kidney. We present the results of a survey of 55 myxosporean species that determined that this antibody detects an antigen on the spore surface of 33 of these species in the generaMyxobolus,SphaerosporaandThelohanellus. However, there appears to be no clear relationship between those spores that contain the MAb B4 reactive antigen and the host or organ in which they are detected. The antigen appears to be synthesized in the plasmodial cytoplasm and is intimately associated with the surface of the spore capsules and, where present, the mucus envelope. The nature of this envelope is further discussed in relation to its formation and distinctive properties.

Synopsis of the species of Myxobolus Butschli, 1882 (Myxozoa: Myxosporea: Myxobolidae)

A synopsis of 744 nominal species of Myxobolus Butschli, 1882 (Myxozoa, Myxosporea, Myxobolidae) is presented. For each species, the relevant morphometric and morphological data are indicated, as well as the host(s), site(s) of infection within the host and type-locality.

Histopathological changes caused by the metacestodes of Neogryporhynchus cheilancristrotus (Wedl, 1855) in the gut of the gibel carp, Carassius gibelio

Metacestodes of Neogryporhynchus cheilancristrotus (Wedl, 1855) were found in the gut of some gibel carp (Carassius gibelio) specimens from a Hungarian water reservoir. Location of metacestodes in the freshly opened gut was marked with disseminated, red-coloured, pinhead-sized nodules in the anterior part of the intestine. In histological sections, metacestodes were found in a hole inside the propria layer of the intestinal folds. The worms were in direct contact with the host tissue without being encapsulated as a result of host reaction. In some specimens with extruded rostellum the rostellar hooks were bored into the host tissue and suckers grabbed pieces of the surrounding connective tissue. Around the worms, congested capillaries and formation of macrophages were seen in the lysed connective tissue.

Disease course, frequency of relapses and survival of 73 patients with juvenile or adult dermatomyositis

OBJECTIVE

Our aim is to present the disease course, frequency of relapses and survival of juvenile and adult dermatomyositis (JDM/DM) patients.

METHODS

Analysis was performed using data on 73 patients. The median follow-up for 38 JDM patients was 32 months and 78 months for 35 adult DM patients.

RESULTS

23/38 JDM patients (60%) had monophasic, 12/38 (31.6%) had polycyclic and 3/38 (7.9%) had chronic disease. Among children treated only with glucocorticoids, 12/20 (60%) had monophasic and 8/20 (40%) had polycyclic disease. 10/17 (58.8%) children, who required second-line immunosuppressive agents, had monophasic and 4/17 (23.5%) had polycyclic disease. 18/35 DM (51.4%) patients had monophasic, 13/35 (37.1%) had polycyclic, 1/35 (2.9%) had chronic disease and 3/35 (8.6%) had fulminant myositis. Among DM patients requiring only glucocorticoids, 12/20 (60%) were monophasic and 8/20 (40%) were polycyclic. In patients requiring second-line immunosuppressive agents, 6/15 patients (40%) had monophasic and 5/15 (33.3%) had polycyclic disease. Among patients with polycyclic disease, the risk of relapse was higher during first year than later in the disease course. None of the JDM patients have died, while 4 disease-specific deaths occurred in adult patients. There was no significant difference between the survival of JDM and DM patients.

DISCUSSION

There was no correlation between relapse-free survival and the initial therapeutic regimen. Many of our patients had polycyclic or chronic disease. As relapses can occur after a prolonged disease-free interval, patients should be followed for at least 2 years. Although we found a favourable survival rate, further investigations are needed to assess functional outcome.

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.

Occurrence and pathology of Sinergasilus lieni (Copepoda: Ergasilidae), a parasite of the silver carp and bighead, in Hungarian ponds

Sinergasilus lieni Yin, 1949, a well-known and pathogenic parasitic copepod in China and Russia, has been detected in Hungarian carp farms for the first time. The parasite infected the third-year generation of silver carp (Hypophthalmichthys molitrix) and bighead (Aristichthys nobilis). The gills of the infected fish specimens showed severe pathological changes. At the attachment sites of female copepods clubbing and fusing of the gill filaments were observed and in some parts of the pale or whitish hemibranchia deep indentations were recorded in places where the tips of the damaged filaments had broken off. Silver carp and bighead were infected at a similar rate, having 8 to 27 copepods attached to the end of the clubbed filaments or the proliferated epithelium of 2 to 10 fused filaments. In histological sections the head part of the parasite was found in a deep cavity of the proliferated epithelium, piercing its antennae deep into the tissues. Only the end of the filaments showed changes. In this part the proliferated epithelium was infiltrated by eosinophilic granular cells. In the central and basal parts of the hemibranchia the original structure of the filaments was preserved with intact secondary lamellae.

Reno-, hepato- and splenomegaly of common carp fingerlings (Cyprinus carpio L.) diseased in swimbladder inflammation caused by Sphaerospora renicola Dyková et Lom, 1982

The weight of internal organs (swimbladder, kidney, liver, spleen) in relation to the body weight was studied in common carp fingerlings divided into three groups on the basis of swimbladder appearance and microscopic examination of the kidney. The fish had been collected from different Hungarian fish farms at the time when swimbladder inflammation (SBI) usually occurs (in July and August). The first group comprised fish with severe signs of SBI and massive renal sphaerosporosis, the second group consisted of fish with milder swimbladder changes and/or kidney infection by a low number of Sphaerospora renicola, while the third group was constituted by infection-free common carp fry. Statistical analysis of swimbladder, kidney, liver and spleen weight in relation to the body weight revealed that in the infected groups the internal organs were substantially enlarged. This suggests that in common carp fry with SBI the swimbladder changes are accompanied by reno-, hepato- and splenomegaly.

A survey of coccidian infections of freshwater fishes of Peninsular Malaysia, with descriptions of three species of Goussia Labbé, 1896 (Apicomplexa: Eimeriidae)

Ninety-five specimens of 14 freshwater fish species from small streams in the Kuala Terengganu district and the Lake Kenyir Reservoir, Malaysia, were surveyed for coccidian infections. Six fish species proved to be infected with apicomplexans belonging to the genus Goussia. In all of these fishes Goussia species were found in unsporulated and semisporulated stages. Oöcysts of four species inhabiting the intestinal epithelium became sporulated in tap-water within 24 hours. In two fish species sporulation failed and only unsporulated oöcysts were recorded in the intestine. Three of the intestinal species finishing sporulation proved to be new to science and were described as Goussia malayensis n. sp., G. bettae n. sp. and G. pogonognathi n. sp. from Apocheilus panchax, Betta splendens and Hemirhamphodon pogonognatus, respectively. The fourth species, found in Trichogaster pectoralis, was identified as G. trichogasteri Székely & Molnár, 1992, a species known from aquarium-cultured T. trichopterus.

A potential dual apical pathway in polarized regenerative cells of the midgut of Manduca sexta

Two novel proteins with apparent molecular weight of 38 (Manduca sexta midgut MsM38) and 46kDa (MsM46) were isolated from midgut homogenates in wandering stage Manduca sexta larvae and both of them were found to be present exclusively in this tissue on Western blots. Immunocytochemical studies revealed that both proteins are expressed in the regenerative cells however, their distribution pattern is clearly different. MsM38 is localized in the cytoplasm of resting regenerative cells during the feeding period, and is accumulated in the calcospherits at the beginning of the wandering period. Along with the delamination of the larval epithelium, this protein is released apically from these vesicles. The antiserum labels an additional 76 kDa protein in the wandering larval midgut homogenates. The appearance of this 76 kDa protein coincides with the accumulation of the immunopositive material in the calcospherits. MsM46 is similarly distributed during the feeding period in the cytoplasm of regenerative cells. At the beginning of the wandering period it accumulates around the newly forming large apical vacuoles, that are released at the time of complete delamination of the larval epithelium. In parallel with this process MsM46, and another 40 kDa protein, that becomes labeled from this period on Western blots appeares on the apical microvillar projections. Thus both isolated proteins are directed apically from different compartments, that raises the possibility of a dual apical routing pathway in regenerative cells.

The immunoprotein scolexin and its synthesizing sites--the midgut epithelium and the epidermis

Scolexin is one of the bacterial induced hemolymph proteins of tobacco homworm (Manduca sexta) larvae, that has hemocyte coagulation-provoking activity. The 72 kDa scolexin complex is composed of two 36 kDa subunits. To examine the protein secretory pathways in insect epithelia a polyclonal antibody was raised against the 36 kDa hemolymph protein. This MsH36 antibody recognised a 36 and a 72 kDa protein in tissue homogenates. On the basis of the characteristic labelling pattern observed on immunoblots and immunocytochemical sections we concluded that the 36 kDa protein in the hemolymph, in the midgut and in the epidermis was identical with the scolexin subunit. In present paper we report a labelling shift in the midgut epithelium between goblet and columnar cells that may be controlled by the hormonal system. A 72 kDa protein showed similar epitops and molecular weight to the scolexin complex and was detected in epidermis and in cuticle under both reducing and non-reducing conditions. Tissue localization of 36 kDa and 72 kDa MsH36 antibody labelling proteins indicated the possibility that the epidermal cells produce two kinds of scolexin-like proteins. The complex composed of 36 kDa subunits are transported basolaterally into the circulation and display hemocyte coagulation inducing activity while the 72 kDa form contains two subunits linked covalently secreted apically into the cuticle.

Development of Myxobolus macrocapsularis (Myxosporea: Myxobolidae) in an oligochaete alternate host, Tubifex tubifex

The development of Myxobolus macrocapsularis Reuss, 1906, a myxosporean parasite of the gills of common bream Abramis brama L., was studied in experimentally infected oligochaetes. In 3 experiments uninfected Tubifex tubifex Muller and Limnodrilus hoffmeisteri (Claparéde) were exposed to mature myxospores of M. macrocapsularis. In all experiments, typical triactinospores developed in T. tubifex specimens but no infection was found in L. hoffmeisteri. Triactinospores were released from oligochaetes 66 to 99 d after initial exposure. At that time pansporocysts containing 8 triactinospores were located in the gut epithelium of experimental oligochaetes, but free actinosporean stages were also found in the gut lumen of the oligochaetes. Each triactinospore had 3 pyriform polar capsules and a barrel-shaped sporoplasm with 32 secondary cells. The spore body joined the 3 caudal projections with a stout style.

Differences between the European carp (Cyprinus carpio carpio) and the coloured carp (Cyprinus carpio haematopterus) in susceptibility to Thelohanellus nikolskii (Myxosporea) infection

Thelohanellus nikolskii infection of the common carp (Cyprinus carpio L.) has been a common parasitosis in the Central European fish farms since the first detection of the parasite about 20 years ago. This parasite, introduced from the Far East, causes intensive infection on the fins of fingerlings of the carp subspecies cultured in Europe (European carp, Cyprinus carpio carpio). This infection of the common carp occurs in the Hungarian fish farms every year. Until the present study, this parasite had not been recorded from the fins of koi or coloured carp (Cyprinus carpio haematopterus), a carp of Far Eastern origin, which is cultured in Hungary as an ornamental fish. A recent survey conducted in common carp, koi and goldfish stocks demonstrated that T. nikolskii infection of low prevalence and intensity occurs also in koi populations, but its prevalence and intensity are markedly lower than in common carp kept in the same ponds. It is suggested that the observed differences are due to disparities in the susceptibility of the two carp subspecies to T. nikolskii, and that the koi is less susceptible to this infection. Other signs of susceptibility can also be observed in the European subspecies, since in 15% of the fish plasmodium development was arrested at an early stage. Thelohanellus nikolskii infection could not be demonstrated on goldfish (Carassius auratus).

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.

Antineutrophil cytoplasmic antibodies in patients with systemic lupus erythematosus

We determined the prevalence of antineutrophil cytoplasmic antibodies (ANCAs) in patients with systemic lupus erythematosus (SLE) and evaluated the correlation between ANCA positivity and clinical features. Forty-one patients with SLE and two control groups were examined. One of the control groups consisted of 15 patients with systemic vasculitis, and the other of 12 healthy blood donors. A quantitative enzyme-linked immunosorbent assay technique was used to measure the serum cytoplasmic ANCA (cANCA) and perinuclear ANCA (pANCA) levels. cANCA positivity was found in three patient samples, and pANCA positivity in 10 SLE patients. The occurrence and titres of both ANCA types in SLE patients were similar to those in healthy controls and significantly lower than those in patients with systemic vasculitis. The clinical picture and antibody profile were similar in ANCA-positive and ANCA-negative SLE patients. We conclude that measurement of ANCAs does not provide any additional diagnostic or prognostic data in SLE.

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.

Distribution of serpins in the tissues of the tobacco hornworm (Manduca sexta) larvae. Existence of new serpins possibly encoded by a gene distinct from the serpin-1 gene

Polyclonal antibodies were raised against the isolated hemolymph serine proteinase inhibitors (serpins) of Manduca sexta larvae. Two of these antibodies, MsH49a and MsH49b, displayed characteristic differences in labelling patterns of hemocytes, fat body, integumental epidermis and cuticle on immunoblots, and in light- and electronmicroscopic sections. The serpin composition of the latter three tissue homogenates was determined by native immunoblots and inhibitor binding assays. The results were compared to the hemolymph samples containing all the known inhibitors encoded by the well-characterized serpin-1 gene. The enzyme specificity of the MsH49b-labelled cuticular serpin was similar to serpin-1J, although its electrophoretic mobility on native PAGE was not identical with any of the known proteinase inhibitors encoded by the serpin-1 gene. Based on these data, we suggest that the cuticle and hemolymph may contain novel serpin(s) encoded by a gene other than the serpin-1 gene. Since the serpin-1J proved to be involved in the activation pathway of the prophenoloxidase system in the hemolymph, the in vivo function of cuticular MsH49b serpin was investigated by prophenoloxidase tests in native cuticular homogenates. Our results demonstrated that the cuticular serpin(s) that are labelled by the MsH49b antibody may play a determinant role in the regulation of the prophenoloxidase system of the integumental cuticle.

Survey on Myxobolus infection of the bleak (Alburnus alburnus L.) in the river Danube and in Lake Balaton

In a three-year survey of myxosporean infections of the bleak (Alburnus alburnus), involving the examination of 205 fish specimens from the River Danube and 50 from Lake Balaton, four Myxobolus species (two gill parasites, one fin parasite and a species parasitising the skeletal muscles) were detected. Two of the species could be identified as M. alburni and M. obesus. Of the other two species, the gill parasite proved to be a hitherto undescribed species which is described here as a new species by the name of M. margitae. One of the two gill-parasitic species, M. obesus, formed plasmodia in the respiratory lamellae of the gill filaments, while the plasmodia of M. margitae n. sp. were formed in the afferent artery of the primary gill filaments. The plasmodia containing spores morphologically identifiable with the species M. alburni were located in the connective tissue between the fin rays. The less frequently found muscle-parasitic Myxobolus species has not been identified precisely. The plasmodia of M. obesus were found in the fish in May and June, while those of M. alburni and M. margitae n. sp. in July and August. The prevalence of infection in fish examined in these periods was 15.5% for M. obesus, 11.5% for M. margitae and 14.0% for M. alburni.

Myxobolus intrachondrealis sp. n. (Myxosporea: Myxobolidae), a parasite of the gill cartilage of the common carp, Cyprinus carpio

A species not identifiable with any of the about 23 Myxobolus species recorded from the common carp so far, was detected in the gills of one- and two-summer-old specimens of the common carp ((Cyprinus carpio L.) cultured in pond farms in Hungary. The strictly tissue-specific plasmodia of the parasite were located, surrounded by hyaline cartilage cells, in the chondrous substance of the terminal parts of the gill arches and in the cartilage structure ventrally connecting the gill arches. The spores of the parasite described as Myxobolus intrachondrealis sp. n. developed in globular or ellipsoidal plasmodia measuring 300-600 microm. By their elongated ellipsoidal shape and similarly elongated polar capsules the spores were well distinguishable from the hitherto described Myxobolus species parasitic in the common carp and also from the cartilage-parasitic Myxobolus species of other fishes.

Identification of fish-parasitic Myxobolus (Myxosporea) species using a combined PCR-RFLP method

Polymerase chain reaction (PCR) with primers specific for the family Myxobolidae was used to amplify a part of the 18S ribosomal RNA gene of Myxobolus species. The length of the amplified fragments was approximately 1600 base pairs. Six Myxobolus species identified on the basis of morphological features were compared using a combined PCR-RFLP method. The cleavage patterns generated by 2 frequent cutter restriction enzymes (HinfI and MspI) were suitable for the differentiation of the examined Myxobolus species.

A survey on coccidian infection of Lake Biwa fishes in Japan, with the description of four new species of Goussia labbe, 1896 (Apicomplexa)

Thirty-two specimens of 11 freshwater fish species from Lake Biwa, Japan were surveyed for coccidian infections. Four fish species proved to be infected with apicomplexans belonging to the genus Goussia. Altogether, seven Goussia species were found. Oöcysts of four species inhabiting the intestinal epithelium were shed at the sporulated stage. Two other intestinal species left the fish unsporulated. A few relatively large and aged oöcysts of a further species were found in the renal tubules. The sporulated intestinal species were described as Goussia biwaensis n. sp., G. grygieri n. sp., G. nipponica n. sp. and G. wakabayashii n. sp.

Development of a system for detection of circulating antibodies against hemidesmosomal proteins in patients with bullous pemphigoid

Specific antibodies directed against special hemidesmosomal proteins are involved in the pathogenesis of bullous pemphigoid (BP), and detection of these antibodies is crucial for a correct diagnosis. As the BP autoantigen primary structures are known, the question was addressed as to whether it is possible to demonstrate circulating antibodies against BP autoantigens (BPAG1 and BPAG2) by means of an ELISA system, using antigenic epitopes. With the help of the programs Peptidestructure and Plotstructure, antigenic epitopes of BP antigens were predicted, chemically synthesized and screened using serum from 43 proven BP patients. The coding sequences of the best antigenic epitopes were then chemically synthesized and inserted as monomer and homo- or hetero-oligomer forms into fusion-expression plasmids (PGEX-4T, Pharmacia) in-frame to the C-terminus of glutathione-S-transferase. Fusion products were expressed and purified from Escherichia coli cells by affinity chromatography. The recombinant proteins were used for the detection of antibodies in the serum of 43 BP patients and of 60 controls (including 30 healthy persons, 22 patients with pemphigus vulgaris and 8 patients with other bullous dermatoses). Use of the homo- and hetero-oligomers of the recombinant fusion peptides increased the sensitivity of the disease-specific antibody detection. When a mixture of the best recombinant fusion proteins was used, the sensitivity of the ELISA assays in the case of the BP patients' serum was 0.90. This system could form the basis of a rapid and simple system for the diagnosis of BP.

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.

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.

Redescription of Myxobolus hungaricus Jaczó, 1940 (Myxosporea: Myxobolidae), a parasite of bream (Abramis brama L.)

Myxobolus hungaricus Jaczó, 1940 forms relatively large plasmodia on the gills of bream (Abramis brama). The authors give a redescription of this deficiently described parasite on the basis of spores collected from the original habitat, which spores are indicated as a neotype. The plasmodia of the parasite can be found on the gills typically in the spring months, and are located in the central part of the gill filaments. They start to develop in the lumen of capillaries of the secondary lamellae and remain in intralamellar location also after they have reached the mature stage. The spores have a very characteristic shape, as on the surface of the spore valves a distinctly emerging ridge runs parallel to the sutural line. In addition to breams from the typical habitat, Lake Balaton, the plasmodia of M. hungaricus could be detected also on breams originating from the river Danube.

Isolation and characterization of an apically sorted 41-kDa protein from the midgut of tobacco hornworm (Manduca sexta)

Immunocytochemical localization and sorting properties of a newly purified 41-kDa protein (MsM41) were investigated in an insect, the tobacco hornworm Manduca sexta. The protein purified from midgut homogenates of feeding fifth-stadium larvae was found exclusively in this tissue on Western blots. Presence of MsM41 protein was indicated in both anterior and posterior regions of the midgut during the whole fifth stadium. However, in the posterior region an additional 39-kDa protein was also detected during the feeding period of the last larval stage. Upon light-microscopic examination immunoreactivity was localized in the columnar cells, while the goblet, endocrine and regenerative cells remained unlabeled. Distribution of the label during the feeding period was different in the anterior and posterior regions. In the anterior region immunoreactivity was localized only to the brush border membrane of columnar cells, while in the posterior region some cytoplasmic structures identified as large trans-Golgi vesicles, endoplasmic reticulum and small secretory vesicles were also labeled. Large, apical extrusions remained immunonegative. In vitro translation confirmed that our protein was expressed only in the posterior region of the midgut. The primary translation product was a 39-kDa protein. Putative post-translational modifications yielded the 41-kDa form, which was then secreted apically. Its presence in the region of the anterior part microvilli was probably due to the countercurrent flux of the ectoperitrophic fluid.

Insect cuticle, an in vivo model of protein trafficking

In the course of this study more than 20 proteins have been isolated from the larval cuticle of Manduca sexta. Synthesis, secretion, transport and accumulation of four particular proteins, representative members of four characteristic groups, were followed during metamorphosis by immunoblot and immuncytochemical methods and are described in detail in this paper. We established that only some of the proteins of the soft cuticle of Lepidopteran larvae are synthesized in epidermal cells at the beginning of the larval stages and are digested during the moulting period (MsCP29). Other proteins (MsCP30/11) are secreted into the cuticle by the epidermal cells in different forms during various developmental stages. Some proteins are secreted apically during the feeding period, but before ecdysis they are then taken up by epidermal cells and transported in a basolateral direction back into the hemolymph and saved in an immunologically intact form by the fat body cells (MsCP12.3). Some cuticle proteins have a non-epidermal origin. They are transported from the hemolymph into the cuticle. Before and during ecdysis these molecules reappear in the hemolymph and are detectable again in the pupal cuticle (MsCP78). Our data prove that the cuticle is not a non-living part of the insect body: it is not only an inert, protective armor, but maintains a continuous and dynamic metabolic connection with the other organs of the organism.

Antineutrophil cytoplasmic antibodies and other immunologic abnormalities in patients with habitual abortion

PROBLEM

The immunologic mechanisms of pregnancy loss in habitual aborters with antiphospholipid and antinuclear antibodies have not been fully clarified. The possible association of antineutrophil cytoplasmic antibodies (ANCAs) with recurrent miscarriage was examined.

METHOD OF STUDY

In a prospective, controlled trial of 59 women with recurrent abortion, the prevalence of pANCA (antimyeloperoxidase), cANCA (antiproteinase-3), and immunoserologic abnormalities of systemic lupus erythematosus (SLE) anti double-stranded DNA, anti-SSA, anti-SSB, anti-U1RNP, anti-Sm, anticardiolipin and antinuclear antibodies, LE-cell, lupus anticoagulant, and complement-3 were investigated.

RESULTS

pANCA occurred in 2, and cANCA in 6 of 59 case patients, but neither was observed in the controls (P = 0.09 for cANCA). cANCA levels were significantly higher in patients than in controls (P = 0.028). Six recurrent aborters were identified as having a group of immunoserologic abnormalities characteristic of SLE.

CONCLUSIONS

Immunologic mechanisms detectable in SLE may operate in a subgroup of habitual aborters with suspected immunologic cause. ANCAs occur more frequently in patients with recurrent miscarriage than in controls.

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.