Myxosporean Infections in Cultured Tilapias in Israel1

Five new species of myxosporean parasite are described from cultured tilapias in Israel. These are: Myxosoma sarigi. Myxosoma equatorialis, Myxobolus israelensis. Myxobolus agolus, and Myxobolus galilaeus. The first four were found in hybrids of Oreochromis aureus x Oreochromis niloticus while Myxobolus galilaeus was found in Sarolherodon galilaeus. In addition, M. sarigi. M. israelensis, and Myxobolus sp. were also found in S. galilaeus. In the light of the present study, the taxonomy of myxosporean infections in tilapias is modified. Mature spores may localize in the melano-macrophage centers of the spleen and kidney where ihey may eventually be destroyed. Nc cases of mortality have so far been associated with these parasites.     

Occurrence of myxosporean parasites in the gills of two tilapia species from Lake Nokoué (Bénin, West Africa): effect of host size and sex, and seasonal patterns of infection

The gill myxosporean parasites of 2 euryhaline tilapias from Lake Nokoué, Sarotherodon melanotheron melanotheron (Rüppel, 1853) and Tilapia zillii (Gervais, 1852), were investigated from October 1987 to October 1989. A total of 391 S. m. melanotheron and 222 T. zillii were examined. Both of the fish species studied were infected by 3 host-specific myxosporean parasites for which prevalence greatly varied during our investigations. The 2 most common ones were Myxobolus sp. and M. zillii, which were located in the branchial filament. No significant fish sex effect was found for these 6 different myxosporean parasites. As seasonal pattern was clearly demonstrated for M. zillii while a host size effect was found for M. dossoui. However, further investigations of these myxosporean infections are necessary to determine the real effect of these parasites on their host, as host fecundity and survival was not assessed.     

Henneguya mbakaouensis sp. nov., Myxobolus nounensis sp. nov. and M. hydrocyni Kostoingue & Toguebaye, 1994, Myxosporea (Myxozoa) parasites of Centropomidae, Cichlidae and Characidae (Teleosts) of the Sanaga basin in Cameroon (Central Africa)

The study of 102 teleost freshwater fishes of Sanaga basin in Cameroon revealed the presence of three myxosporean species, among which two were new. Host fishes were of three families: Centropomidae, Cichlidae and Characidae. New species were identified as Henneguya mbakaouensis sp. nov., a gill parasite of Lates niloticus and Myxobolus nounensis sp. nov. found in the kidney and spleen of Sarotherodon galilaeus and Tilapia mariae. Myxobolus hydrocyni Kosto?ngue & Toguebaye, 1994, previously described in Chad, was also found in Cameroon; complementary informations were given on that parasite which seemed to be specific to its host.     

The Nature of the Iodinophilous Vacuole of Myxosporidan Spores, and a Proposal to Synonymize the Genus Myxosoma Thélohan, 1892 with the Genus Myxobolus Bütschli, 1882

SYNOPSIS. The myxosporidan genera Myxobolus and Myxosoma differ only by the presence or absence of a so-called iodinophilous vacuole in their spores which has in the past been shown to contain glycogen. In the present study, spores of Myxobolus pseudodispar, M. cyprini, M. muelleri, Myxosoma heterospora and Agarella gracilis were tested for glycogen using Best's carmine, iodine, and the Bauer-Feulgen technic. These tests showed that (a) Glycogen was present in variable amounts in spores of each species. In some spores this took the form of a vacuole, while in others the distribution was diffuse or particulate; (b) In no species of Myxobolus did the majority of spores contain a vacuole; (c) In Myxosoma heterospora vacuoles were present in a small proportion of spores. It is concluded that the iodinophilous vacuole cannot be used as a taxonomic criterion in the Myxosporida, and therefore that the genus Myxosoma should be synonymised with the genus Myxobolus .     

A new record of Myxobolus brachysporus and M. israelensis in the tilapia (Oreochromis niloticus) collected from the Nile River,Egypt

The present study was carried out as part of an ongoing general survey for myxosporean parasites infecting tilapias in the River Nile, Egypt. In the present study, 77 Nile tilapia (Oreochromis niloticus) were collected from boat landing sites at Beni-Suef governorate, Egypt and examined for the myxosporean infection. The infection was encountered as a huge number of free spores in the kidney and the spleen. The infection showed a prevalence of 51.9% (40/77) for Myxobolus brachysporus while it was 25.9% (20/77) for Myxobolus israelensis. Mature spores of M. brachysporus were ellipsoidal and measured 8.6 × 13.2 μm. The polar capsules were subcircular with 5–6 filament turns and measured 4.7 × 3.6 μm. Spores of M. israelensis were ellipsoidal in the frontal view and fusiform in the lateral view. Spore measurements were 13.4 μm long and 8.7 μm wide. The polar capsules were elongated with 6–7 filament coils and measured 8.6 × 3.1 μm. The findings presented here proved that tilapia fishes in the Nile River are still suffering from infections with Myxobolus species. Therefore, further studies should be carried out to survey the Myxobolus infection among tilapias under culture conditions to clarify the pathological impacts of this parasite in tilapias aquaculture.     

Myxosporea parasites in roach, Rutilus rutilus (Linnaeus), from four lakes in central Finland

Ten myxosporean species belonging to three families were found in roach, Rutilus rutilus (Linnaeus), obtained in 1985 and 1986 from four lakes in central Finland which are connected to each other, but differ in water quality. One of the lakes is polluted by paper and pulp mill effluent, two are eutrophic and one is oligotrophic and still in its natural state. Eight species were found in all the lakes. The most common species were Myxidium rhodei Léger, 1905, Myxobolus muelleri Bütschli, 1882 and Myxobolus pseudodispar Gorbunova, 1936 with prevalences varying between 66–80, 16–31 and 32–59%, respectively, in the four lakes. The largest difference in myxosporean prevalence between lakes was found in the case of M. pseudodispar infection, which was highly significantly lower in the polluted lake. The locations of the myxosporean species in the tissues of the fish were found to be species-specific. M. rhodei and M. muelleri being prevalent in the kidney and M. pseudodispar in the muscles.
No clear seasonal variation was found but a tendency for a decrease in infection with increasing age was recorded in the case of M. rhodei and M. pseudodispar .     

Molecular characterization of the myxosporean associated with parasitic encephalitis of farmed Atlantic salmon Salmo salar in Ireland

During seasonal epizootics of neurologic disease and mass mortality in the summers of 1992, 1993 and 1994 on a sea-farm in Ireland, Atlantic salmon Salmo salar smolts suffered from encephalitis associated with infection by a neurotropic parasite. Based on ultrastructural studies, this neurotropic parasite was identified as an intercellular presporogonic multicellular developmental stage of a histozoic myxosporean, possibly a Myxobolus species. In order to generate sequence data for phylogenetic comparisons to substantiate the present morphological identification of this myxosporean in the absence of detectable sporogony, polymerase chain reaction (PCR), Southern blot hybridization, dideoxynucleotide chain-termination DNA sequencing, and in situ hybridization (ISH) were used in concert to characterize segments of the small subunit ribosomal RNA (SSU rRNA) gene. Oligonucleotide primers were created from sequences of the SSU rRNA gene of M. cerebralis and were employed in PCR experiments using DNA extracted from formalin-fixed paraffin-embedded tissue sections of brains from Atlantic salmon smolts in which the myxosporean had been detected by light microscopy. Five segments of the SSU rRNA gene of the myxosporean, ranging in length from 187 to 287 base pairs, were amplified, detected by hybridization with sequence-specific probes, and sequenced. Consensus sequences from these segments were aligned to create a partial sequence of the SSU rRNA gene of the myxosporean. Assessments of sequence identity were made between this partial sequence and sequences of SSU rRNA genes from 7 myxosporeans, including Ceratomyxa shasta, Henneguya doori, M. arcticus, M. cerebralis, M. insidiosus, M. neurobius, and M. squamalis. The partial SSU rRNA gene sequence from the myxosporean had more sequence identity with SSU rRNA gene sequences from neurotropic and myotropic species of Myxobolus than to those from epitheliotropic species of Myxobolus or Henneguya, or the enterotropic species of Ceratomyxa, and was identical to regions of the SSU rRNA gene of M. cerebralis. Digoxigenin-labeled oligonucleotide DNA probes complementary to multiple segments of the SSU rRNA gene of M. cerebralis hybridized with DNA of the parasite in histologic sections of brain in ISH experiments, demonstrating definitively that the segments of genome amplified were from the organisms identified by histology and ultrastructural analysis. Based on sequence data derived entirely from genetic material of extrasporogonic stages, the SSU rDNA sequence identity discovered in this study supports the hypothesis that the myxosporean associated with encephalitis of farmed Atlantic salmon smolts is a neurotropic species of the genus Myxobolus, with sequences identical to those of M. cerebralis.     

Small Subunit Ribosomal RNA Sequences Unite Alternate Actinosporean and Myxosporean Stages of Myxobolus cerebralis the Causative Agent of Whirling Disease in Salmonid Fish

ABSTRACT. The alternating myxosporean and actinosporean stages of the myxozoan parasitc Myxobolus cerebralis (Hofer 1903) from its salmonid fish and aquatic oligochaete hosts, respectively, were compared for sequence homology of the small subunit (18S) ribosomal RNA genes. A 99.8% similarity between the sequences of these two stages was substantially greater than that of M. cerebralis compared to two other Myxobolus sp. from salmonid fish. Our results are the first molecular evidence confirming the alternating stages initially described by Wolf and Markiw [25] for the life cycle of M. cerebralis but found in two different taxonomic classes (Myxosporea and Actinosporea) are indeed forms of the same organism. Sequencing of rRNA genes of the actinosporean stage followed by development of specific primers for DNA amplification of the myxosporean stage, as in our study, should be applied to solve other myxozoan life cycles. Additionally, these approaches will in the future provide useful diagnostic reagents for the detection and study of this important group of fish pathogens.     

Revision of Myxobolus heterosporus Baker, 1963 (syn. Myxosoma Heterospora) (Myxozoa: Myxosporea) in African records

There is uncertainty regarding the validity of Myxobolus heterosporus Baker, 1963. The present study revises the taxonomy, using specimens isolated from plasmodia situated in the infected cornea of Oreochromis aureus, O. niloticus or Tilapia zillii inhabiting the River Nile, Egypt. In addition, histological effects of the parasite on the infected tissue were examined. The spores of M. heterosporus had a variety of shapes expressing remarkable heteromorphism. Five main Myxobolus-like spore types and tailed-spores were found. All forms were photographed, measured, sketched and described. Light and electron microscopy supported that spores of a Myxobolus-like morphology co-existed with so-called tailed-spores in one plasmodium. Some transitional stages from Myxobolus-like spore types to tailed-spores were observed. Therefore, some tailed-spores may be simply heteromorphs of Myxobolus.     

鲤肠道寄生岳阳碘泡虫新种的形态特征及系统发育分析

在洞庭湖岳阳地区开展鱼类寄生虫调查中,发现一种寄生于鲤Cyprinus carpio L.肠道的黏孢子虫。该黏孢子虫的孢囊呈白色,椭圆形,大小为(1.0±0.2) mm (0.8—1.2 mm)。成熟孢子具有壳瓣,壳面观近似圆形,后端有4—6个“V”形褶皱;缝面观呈纺锤形,缝脊直而粗;孢质均匀,含有一个嗜碘泡;孢子长(9.8±0.6) μm (9.6—10.0 μm),孢子宽(8.2±0.3) μm (8.0—8.5μm),孢子厚(7.3±0.1) μm (7.0—7.5 μm);2个极囊梨形,位于孢子顶端,大小相等,呈“八”字形;极囊长(4.4±0.4) μm (3.8—5.1 μm),宽(2.7±0.2) μm (2.2—3.2 μm),极丝4—5圈。该黏孢子虫与肠膜碘泡虫、丑陋圆形碘泡形态特征非常相似,但其极囊/孢子小于1/2;与文献已报道的鲤肠道寄生北京碘泡虫和鲤肠碘泡虫相比较,其在孢子形态、孢子和极囊大小方面分别存在明显差异。基于该黏孢子虫18S rDNA基因序列(GenBank登录号KY203795)比对分析,该黏孢子虫与山东碘泡虫相似率最高,仅为96%。系统发育分析发现,该黏孢子虫与山东碘泡虫、倪李碘泡虫、住心碘泡虫、Myxobolus encephalicus、Sphaerospora molnari、多涅茨尾孢虫和Henneguya zikaweiensis聚为独立分支,和其他已报道的黏孢子虫亲缘关系较远。综合形态学和18S rDNA基因序列数据,文章报道的鲤肠道寄生黏孢子虫为碘泡虫属一新物种,将其命名为岳阳碘泡虫。     

Mass mortality of pond-reared Carassius gibelio caused by Myxobolus ampullicapsulatus in China

From June to August 2009, allogynogenetic silver crucian carp Carassius gibelio (Bloch) pond-cultured at the Nanquan Experimental Station, China, were found to be heavily infected with myxosporeans, which caused mortalities ranging from 33% (13/40) to 90% (36/40) in the cages. The pharynxes of infected fish were swollen, nodular, and severely damaged. Based on morphological characters and 18S small subunit ribosomal DNA sequence similarity, the myxosporean was identified as Myxobolus ampullicapsulatus. This is the first report of M. ampullicapsulatus causing mass mortality of pond-reared C. gibelio.     

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.     

Spinal curvature of cultured Japanese mackerel Scomber japonicus associated with a brain myxosporean, Myxobolus acanthogobii

Skeletal deformities were found in the cultured Japanese mackerel Scomber japonicus. External and radiographical observations showed the deformed fish to exhibit a dorso-ventral spinal curvature (kyphosis) without fracture or dislocation of the vertebrae. Numerous myxosporean cysts, ca. 0.3 to 1.0 mm in diameter, formed in the 4th ventricle, the cavity of the optic tectum, the surface of the olfactory lobe and bulb, the optic lobe and the inferior lobe of the brain. Spore morphology and molecular analysis of the small subunit ribosomal RNA gene sequence identified the myxosporean parasite as Myxobolus acanthogobii, a parasite which also causes scoliosis in yellowtail Seriola quinqeradiata. Histopathological observation showed that the myxosporean cysts were encapsulated within the host's collagenous layer although some had disintegrated to disperse mature spores into the cranial cavity. Occasionally, lymphocytic infiltration and local granulomatous inflammation were found to be associated with spore dispersion.     

Novel and known myxobolids (Cnidaria,Myxozoa) infecting Chondrostoma angorense (Cypriniformes: Leuciscidae) in Turkey

Turkey has more than 200 endemic freshwater fish species, one of which is the Ankara nase, Chondrostoma angorense Elvira, 1987 (Cypriniformes: Leuciscidae), a food fish in northern Turkey. Like most endemic fish species in Turkey, its myxosporean parasite fauna (Cnidaria: Myxosporea) are not yet described. We surveyed twenty C. angorense from Lâdik Lake in northern Turkey, and identified two myxosporean parasites from gills of these fish: Myxobolus arrabonensis Cech, Borzák, Molnár, Székely, 2015, and a co-infection of a novel species, Myxobolus polati sp. nov. We characterized both infections based on myxospore morphology, morphometry, tissue tropism, small subunit ribosomal DNA sequence and phylogenetic analysis. Plasmodia of both species were observed in gills, but had distinct tropism: M. arrabonensis is an intrafilamental vascular type, and M. polati sp. nov. is an intralamellar vascular type. We identified M. arrabonensis on the basis of myxospore characters and 100% similarity to the type DNA sequence from the closely-related host C. nasus. The small subunit ribosomal DNA sequence of M. polati sp. nov. (1946 base pairs; GenBank Accession number MH392318) had a maximum similarity of 98% with any Myxobolus sp. from other Eurasian cypriniforms. Phylogenetic analysis revealed that M. polati sp. nov. is most closely related to gill-infecting Myxobolus diversicapsularis from Rutilus rutilus (L.). The present study is the first record of myxosporean species infecting C. angorense comprising a novel species, M. polati sp. nov. and a known species M. arrabonensis.     

Myxobolus cycloides on the swimbladder of chub Leuciscus cephalus: a controlled,host-specific localisation

Of 150 wild stock chub, Leuciscus cephalus L. captured in Lower Austrian watercourses, 112 revealed disc like plasmodia of Myxobolus cycloides Gurley, 1893 on the caudal chamber of the swim bladder. Other cyprinid species from the same waters lacked M. cycloides or other myxosporeans in this specific localisation. In chub, the intensity of infection (number of discs on the swim bladder) showed a logarithmic, age-dependent increase. The plasmodia of M. cycloides were situated in the connective tissue--mainly along blood vessels--and exhibited a delicate envelope of host tissue, thus forming a characteristic myxosporean cyst. Occasionally single trophozoites seemed to merge. A general process of fibroblast proliferation leading to encapsulation and degradation of the parasite was observed. This process was initiated by the formation of small multiple encapsulations within the spore containing trophozoid, before thickening of the outer cyst wall occurred. The general non-inflammatory course of the M. cycloides infection, and the obvious good health of the investigated chub suggest that this myxosporean in its host specific localisation cannot be regarded as a serious pathogen--on the contrary: parasite multiplication and degradation seemed to occur in a well-defined equilibrium controlled by the host fish.     

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.     

Myxobolus albi n. sp. (Myxozoa) from the Gills of the Common Goby Pomatoschistus microps Krøyer (Teleostei: Gobiidae)

ABSTRACT. A recent investigation into the myxozoan fauna of common gobies, Pomatoschistus microps , from the Forth Estuary in Scotland, revealed numerous myxosporean cysts within the gill cartilage. They were composed of polysporous plasmodia containing myxobolid spores that were morphologically different from the other known species of Myxobolus and from the myxosporeans previously recorded from this host (i.e. the ceratomyxid Ellipsomyxa gobii , infecting the gall bladder, and the kudoid Kudoa camarguensis , infecting the muscle tissues). Spores were ovoid, 9.4 × 9.1 μm with a thickness of 6.6 μm, with two pyriform polar capsules, the polar filaments of which had four to five turns. Molecular analysis of the parasite's small subunit rDNA region, based upon a contiguous sequence of 1,558 base pairs, discriminated it from other myxosporean species that have been characterized so far. A comparison of the spore morphology and the molecular sequences determined for this new isolate with other myxozoans described to date, confirmed its identity as a previously unknown myxobolid supporting the proposal that this isolate be elevated to the species level as a new species within the genus Myxobolus . A phylogenetic analysis places this new myxobolid, Myxobolus albi n. sp., in a basal position of a clade containing the majority of Henneguya spp. sequenced to date and various Myxobolus spp.     

Detection of Myxobolus rotundus (Myxozoa: Myxosporea) in skin mucus of crucian carp Carassius auratus auratus using a monoclonal antibody

Diagnosis of myxosporean Myxobolus rotundus infection was conducted by examining skin mucus from the infected crucian carp Carassius auratus auratus with a monoclonal antibody, MAb 2D12, raised previously against the parasite. A positive reaction was observed in skin mucus collected from infected fish, and spores and pre-spore stages of the parasite were identified by the MAb 2D12. It was also demonstrated that M. rotundus infection can be successfully detected by a simple method, enzyme-linked immunosorbent assay (ELISA), and that skin mucus collected from infected fish skin had a significantly higher optical density (OD) value than that from uninfected fish.     

Infection patterns of Myxobolus heterospora in two tilapia species (Teleostei: Cichlidae) and its potential effects

A Myxobolus heterospora (Baker, 1963) infection was found in 2 euryhaline tilapia species, Sarotherodon melanotheron melanotheron (Rüppel, 1853) and Tilapia zillii (Gervais, 1852), from a brackish water lake, Lake Nokoué (Benin, West Africa). The histology and ultrastructure of different levels of infection in intestinal connective tissues and wall tissues is described. A total of 391 S. melanotheron melanotheron and 222 T. zillii were examined from October 1987 to October 1989. M. heterospora was found throughout the study period, with a total prevalence of 42.19 and 26.57% for S. melanotheron melanotheron and T. zillii respectively. There was a statistically significant difference in occurrence as a function of season in S. melanotheron melanotheron but not in T. zilli, and there was a significant difference for size and sex in the former and for sex in the latter. M. heterospora induces total destruction of the intestine structure and probably leads to osmoregulatory disturbance. Further investigations of this myxosporean infection are necessary to determine its real effect on the host, since host survival and osmoregulatory rate have not yet been assessed.