The presence of sporogonic stages of Tetracapsuloides bryosalmonae in Icelandic salmonids detected using in situ hybridisation.

Proliferative kidney disease (PKD) is a widespread temperature-dependent disease in salmonids caused by the myxozoan parasite, Tetracapsuloides bryosalmonae (Canning, Curry, Feist, Longshaw et Okamura, 1999) (Tb). Tb has a two-host life cycle, involving fish as an intermediate host and freshwater bryozoans as the definitive host. Although salmonids are acknowledged as hosts for the parasite, it is less clear which fish species are active hosts in the life cycle of Tb. Differences in infection dynamics have been observed between some fish species, which are thought to be related to the existence of two main Tb-strains, the American and European. Iceland, having three species of indigenous salmonids and positioned geographically between Europe and North America, is an ideal location to study the natural development of Tb in wild fish. The main aim of this study was to determine the genetic origin of Tb in Iceland and confirm whether mature spores are produced in Icelandic salmonids. In this study, Icelandic salmonids were infected with the European Tb-strain. In situ hybridisation revealed that intraluminal sporogonic stages, including mature spores, were commonly observed in all three salmonid species. The presence of intraluminal stages has previously been confirmed in brown trout Salmo trutta Linnaeus and Atlantic salmon S. salar Linnaeus in Europe, but they have only been observed in Arctic charr Salvelinus alpinus (Linnaeus) in North America, infected by the local strain. This is, therefore, the first time that sporogonic stages have been observed in Arctic charr in Europe, where fish are infected with the European Tb-strain. Our data strongly suggest that all the three salmonid species inhabiting Icelandic waters serve as active hosts in the life cycle of Tb. However, for full confirmation, transmission trials are needed.

A new species, Henneguya lacustris n. sp. (Cnidaria: Myxosporea), infecting the gills of Astyanax lacustris from Brazil.

The present study describes Henneguya lacustris n. sp. parasitizing Astyanax lacustris (Lütken 1875), from the Tietê River, State of São Paulo, Brazil, through morphological and molecular analysis. Myxospores of the parasites were found in the gills of A. lacustris with 13% prevalence of infection. The myxospores were oval and presented as measures (mean ± standard deviation): total length 18.3 ± 2.2 µm, body length 10.4 ± 1.6 µm, body width 4.9 ± 0.9 µm, tail length 7.2 ± 2.5 µm. The polar capsule was 4.8 ± 0.3 µm long and 1.5 ± 0.2 µm wide. The polar tubules, present inside the polar capsules, had 6 to 7 turns. The ultrastructural analysis allowed the observation of the asynchronous development of the myxospores. Phylogenetic analysis showed H. lacustris n. sp. as a sister species of H. chydadea Barassa and Cordeiro 2003 in a subclade formed by species that parasitize the gills of Characiform fish from Brazil. Using molecular and morphological characterization, this parasite was identified as a new species of the genus Henneguya Thélohan 1892.

Transcriptome of Sphaerospora molnari (Cnidaria, Myxosporea) blood stages provides proteolytic arsenal as potential therapeutic targets against sphaerosporosis in common carp.

BACKGROUND: Parasites employ proteases to evade host immune systems, feed and replicate and are often the target of anti-parasite strategies to disrupt these interactions. Myxozoans are obligate cnidarian parasites, alternating between invertebrate and fish hosts. Their genes are highly divergent from other metazoans, and available genomic and transcriptomic datasets are limited. Some myxozoans are important aquaculture pathogens such as Sphaerospora molnari replicating in the blood of farmed carp before reaching the gills for sporogenesis and transmission. Proliferative stages cause a massive systemic lymphocyte response and the disruption of the gill epithelia by spore-forming stages leads to respiratory problems and mortalities. In the absence of a S. molnari genome, we utilized a de novo approach to assemble the first transcriptome of proliferative myxozoan stages to identify S. molnari proteases that are upregulated during the first stages of infection when the parasite multiplies massively, rather than in late spore-forming plasmodia. Furthermore, a subset of orthologs was used to characterize 3D structures and putative druggable targets. RESULTS: An assembled and host filtered transcriptome containing 9436 proteins, mapping to 29,560 contigs was mined for protease virulence factors and revealed that cysteine proteases were most common (38%), at a higher percentage than other myxozoans or cnidarians (25-30%). Two cathepsin Ls that were found upregulated in spore-forming stages with a presenilin like aspartic protease and a dipeptidyl peptidase. We also identified downregulated proteases in the spore-forming development when compared with proliferative stages including an astacin metallopeptidase and lipases (qPCR). In total, 235 transcripts were identified as putative proteases using a MEROPS database. In silico analysis of highly transcribed cathepsins revealed potential drug targets within this data set that should be prioritised for development. CONCLUSIONS: In silico surveys for proteins are essential in drug discovery and understanding host-parasite interactions in non-model systems. The present study of S. molnari's protease arsenal reveals previously unknown proteases potentially used for host exploitation and immune evasion. The pioneering dataset serves as a model for myxozoan virulence research, which is of particular importance as myxozoan diseases have recently been shown to emerge and expand geographically, due to climate change.

A new myxozoan species Henneguya unitaeniata sp. nov. (Cnidaria: Myxosporea) on gills of Hoplerythrinus unitaeniatus from Mato Grosso State, Brazil.

On the basis of morphological and molecular analyses, a new myxozoan parasite is described from the gills of the fish Hoplerythrinus unitaeniatus, collected in the municipality of Nova Xavantina, Mato Grosso State, Brazil. Plasmodia of Henneguya unitaeniata sp. nov. were oval and whitish and were found surrounded by collagen fibers forming plasmodia wall between gill filaments on the gill arch. The spores were ellipsoidal with two similar polar capsules. Morphometric analysis showed a total spore mean length of 23.8 ± 1.5 µm, spore body mean length of 14.5 ± 0.7 µm, caudal appendage mean length of 10.3 ± 1.4 µm, thickness mean length of 4.3 ± 0.3 µm, polar capsule mean length of 4.2 ± 0.5 µm, polar capsule mean width of 1.8 ± 0.3 µm, spore mean width of 4.8 ± 0.4 µm, and 4-5 polar filament coils. Phylogenetic analysis showed Henneguya unitaeniata sp. nov. as a basal species in a subclade formed by myxozoans that parasitize bryconid fishes.

Kudoa sp. (Myxozoa, Multivalvulida): first report in five commercial fish species from the Canary Islands-FAO 34 (Macaronesia-Spain).

Kudoid myxozoans have been reported causing serious chronic problems in marine fisheries, by reducing the market value of infected fish through pathological damage to the host musculature. We report here the overall prevalence of a Kudoa species in 84/277 (30.3%) fishes from 20 different species of high commercial value captured between October 2011 and December 2013 from the United Nations Food and Agriculture Organization (FAO) 34 commercial fishing area, near the coast of the Canary Islands (Spain). Macroscopic examination showed myxozoan-like cysts in skeletal muscle from 5 of the 20 fish species examined, with the following prevalences: Pagellus acarne (86.7%), Pagellus erythrinus (46.5%), Serranus cabrilla (27.8%), Spondyliosoma cantharus (19.4%), and Sarpa salpa (28.6%). Infection intensity was determined based on spore counts following muscle tissue digestion. Morphometric studies to characterize the species and DNA sequence analysis results suggest that these infections are attributable to a Kudoa species closely related to Kudoa trachuri. This paper reports the first study on a multivalvulidan species to be identified from the Canary Islands. Furthermore, this is the first report of Kudoa parasites in all of the hosts mentioned above, with the exception of P. acarne.

Molecular data infers the involvement of a marine aurantiactinomyxon in the life cycle of the myxosporean parasite Paramyxidium giardi (Cnidaria, Myxozoa).

An aurantiactinomyxon type is described from the marine naidid Tubificoides pseudogaster (Dahl, 1960), collected from the lower estuary of a Northern Portuguese River. This type constitutes the first of its collective group to be reported from Portugal, and only the fourth described from a marine oligochaete worldwide. Extensive morphological comparisons of new aurantiactinomyxon isolates to all known types without available molecular data are proposed to be unnecessary, given the artificiality of the usage of morphological criteria for actinosporean differentiation and the apparent strict host specificity of the group. Recognition of naidid oligochaetes as the hosts of choice for marine types of aurantiactinomyxon and other collective groups, suggests that the family Naididae played a preponderant role in the myxosporean colonization of estuarine communities. Molecular analyses of the type in study further infer its involvement in the life cycle of Paramyxidium giardi (Cépède, 1906) Freeman and Kristmundsson, 2018, a species that infects the kidney of European eel Anguilla anguilla (Linnaeus, 1758) and that has been reported globally, including from Portuguese waters. The low intraspecific difference registered in relation to Icelandic isolates of P. giardi (0.6%) is hypothesized to result from the emergence of genotypically different subspecies due to geographic isolation.

Morphological and Molecular Identification of a Novel Species, Ceratomyxa siganicola n. sp. (Myxozoa: Ceratomyxidae) from Siganus fuscescens, in East China Sea.

INTRODUCTION: Ceratomyxa Thélohan, 1892 is one of the largest genera under Myxosporea Butschli, 1881, and has a worldwide distribution, but little attention has been paid to myxosporean parasites from the Chinese seawaters, East China Sea. METHODS: Morphology and molecular biology methods were combined for species identification and phylogenetic analysis. RESULTS: A new coelozoic myxosporean species, Ceratomyxa siganicola n. sp., was found to infect the gallbladder of Siganus fuscescens (Houttuyn, 1782) (Perciformes, Siganidae) from coastal waters of Xiamen, East China Sea, China. Mature myxospores of the novel species exhibited the morphologically typical features of the genus Ceratomyxa. They were slightly crescent shaped with rounded ends, measuring 5.6 ± 0.5 (4.8-6.5) µm in length and 19.1 ± 1.8 (16.0-22.1) µm in thickness. The posterior angle was slightly convex to straight and measured 177.1 ± 0.5 (175.2-178.4)°. Spore valves were slightly unequal and smoothly ovoid in the lateral view. Two polar capsules were spherical, equal in size and measured 2.7 ± 0.2 (2.1-3.0) µm in diameter. The 18S rDNA sequence of C. siganicola n. sp. was unique among all myxozoans, and the highest similarity was 97.4% with Ceratomyxa barnesi. Phylogenetic analysis showed that C. siganicola n. sp. was clustered within the clade of siganid ceratomyxids. The present results also indicated that the species radiation of Ceratomyxa occurred not only within host affinity but also within locality.

The kinetics of cellular and humoral immune responses of common carp to presporogonic development of the myxozoan Sphaerospora molnari.

BACKGROUND: Sphaerospora molnari is a myxozoan parasite causing skin and gill sphaerosporosis in common carp (Cyprinus carpio) in central Europe. For most myxozoans, little is known about the early development and the expansion of the infection in the fish host, prior to spore formation. A major reason for this lack of information is the absence of laboratory model organisms, whose life-cycle stages are available throughout the year. RESULTS: We have established a laboratory infection model for early proliferative stages of myxozoans, based on separation and intraperitoneal injection of motile and dividing S. molnari stages isolated from the blood of carp. In the present study we characterize the kinetics of the presporogonic development of S. molnari, while analyzing cellular host responses, cytokine and systemic immunoglobulin expression, over a 63-day period. Our study shows activation of innate immune responses followed by B cell-mediated immune responses. We observed rapid parasite efflux from the peritoneal cavity (< 40 hours), an initial covert infection period with a moderate proinflammatory response for about 1-2 weeks, followed by a period of parasite multiplication in the blood which peaked at 28 days post-infection (dpi) and was associated with a massive lymphocyte response. Our data further revealed a switch to a massive anti-inflammatory response (up to 1456-fold expression of il-10), a strong increase in the expression of IgM transcripts and increased number of IgM+ B lymphocytes, which produce specific antibodies for the elimination of most of the parasites from the fish at 35 dpi. However, despite the presence of these antibodies, S. molnari invades the liver 42 dpi, where an increase in parasite cell number and indistinguishable outer cell membranes are indicative of effective exploitation and disguise mechanisms. From 49 dpi onwards, the acute infection changes to a chronic one, with low parasite numbers remaining in the fish. CONCLUSIONS: To our knowledge, this is the first time myxozoan early development and immune modulation mechanisms have been analyzed along with innate and adaptive immune responses of its fish host, in a controlled laboratory system. Our study adds important information on host-parasite interaction and co-evolutionary adaptation of early metazoans (Cnidaria) with basic vertebrate (fish) immune systems and the evolution of host adaptation and parasite immune evasion strategies.

Arrested Development of Henneguya ictaluri (Cnidaria: Myxobolidae) in ♀ Channel Catfish × â™‚ Blue Catfish Hybrids.

Henneguya ictaluri is the etiologic agent of proliferative gill disease (PGD) in farm-raised Channel Catfish Ictalurus punctatus and hybrid catfish in the southeastern United States, and significant annual losses are attributed to this disease. Research suggests that H. ictaluri infection dynamics in Blue Catfish I. furcatus and hybrid catfish (Channel Catfish × Blue Catfish) differ from those in Channel Catfish. Two separate infectivity trials were conducted to investigate H. ictaluri development in Channel Catfish, Blue Catfish, and their hybrids. On two separate occasions with two different year-classes, fish were exposed to pond water containing H. ictaluri actinospores and sampled weekly for 12 weeks (trial 1) or 14 weeks (trial 2). In trial 1, the presence of H. ictaluri was evaluated histologically and by quantitative PCR of fish tissues, including gills, blood, anterior kidney, brain, heart, liver, posterior kidney, spleen, and stomach. Henneguya ictaluri DNA was detected in significantly higher concentrations throughout multiple organ systems in the Channel Catfish compared to the hybrid catfish and Blue Catfish, with the gills having higher quantities. Myxospores were observed in Channel Catfish gill tissue at 8 weeks postexposure. No myxospores were observed in Blue Catfish or hybrid catfish. The second trial focused on gills only and yielded similar results, with Channel Catfish having significantly greater H. ictaluri DNA quantities than hybrids or Blue Catfish across all time points. Myxospores were observed in Channel Catfish beginning at 6 weeks postexposure and were found in 36% (58/162) of Channel Catfish sampled for molecular and histological analysis during weeks 6-14. Myxospores in hybrid catfish were sparse, with single pseudocysts observed in two hybrid catfish (1.2%) at 14 weeks postexposure. These results imply arrested development of H. ictaluri in hybrid catfish. As such, culture of hybrid catfish may be an effective management strategy to minimize the burden of PGD.

Malacosporean myxozoans exploit a diversity of fish hosts.

Myxozoans are widespread and common endoparasites of fish with complex life cycles, infecting vertebrate and invertebrate hosts. There are two classes: Myxosporea and Malacosporea. To date about 2500 myxosporean species have been described. By comparison, there are only five described malacosporean species. Malacosporean development in the invertebrate hosts (freshwater bryozoans) has been relatively well studied but is poorly known in fish hosts. Our aim was to investigate the presence and development of malacosporeans infecting a diversity of fish from Brazil, Europe and the USA. We examined kidney from 256 fish belonging variously to the Salmonidae, Cyprinidae, Nemacheilidae, Esocidae, Percidae, Polyodontidae, Serrasalmidae, Cichlidae and Pimelodidae. Malacosporean infections were detected and identified by polymerase chain reaction and small subunit ribosomal DNA sequencing, and the presence of sporogonic stages was evaluated by ultrastructural examination. We found five malacosporean infections in populations of seven European fish species (brown trout, rainbow trout, white fish, dace, roach, gudgeon and stone loach). Ultrastructural analyses revealed sporogonic stages in kidney tubules of three fish species (brown trout, roach and stone loach), providing evidence that fish belonging to at least three families are true hosts. These results expand the range of fish hosts exploited by malacosporeans to complete their life cycle.

Ceratomyxa azevedoi n. sp. (Myxozoa: Myxosporea) parasitizing the gallbladder of Lutjanus ehrenbergii in the Arabian Gulf.

A novel myxosporean species, Ceratomyxa azevedoi sp. n. is described from the gallbladder of the blackspot snapper, Lutjanus ehrenbergii (Peters), captured from the Arabian Gulf off Saudi Arabia. A total of 45 (26.8%) out of 168 fish specimens were found to be infected with Ceratomyxa azevedoi sp. n., the highest prevalence being observed in winter (42.9%, 18/42) and the lowest in autumn (11.9%, 5/42). Mature spores appeared as crescent to slightly elliptical-shaped, measuring 5-7 (6) µm in length and 12 (10-14) µm in thickness, with spherical polar capsules containing three polar filament coils. The morphometric and morphological comparison with similar species revealed the taxonomic novelty of this form, suggesting that it should be considered as new species. The phylogenetic analysis of C. azevedoi sp. n., based on partial SSU rDNA sequences, revealed close genetic relatedness to C. buri with 91.3% homogeneity and to C. hamour, with 90.1% homogeneity.

[Henneguya wolinensis (Myxosporea: Myxobolidae), a new for Russian fauna parasite from the perch Perca fluviatilis L.].

The infection of the perch Perea fluviatilis L. with myxosporean Henneguya wolinensis Romuk-Wodoracki, 1990 has been detected. This is the second finding of this parasite after its original descriptin and the first for Russia. Plasmodium of this species develops in the epidermis under scales throughout the body causing the formation of white cysts up to 1 mm. Spores are fusiform, large, their average length constitutes 25.5 µm without the caudal appendages and 62 µm with them. Slight morphological differences in spore structure comparing to original description have been revealed.

Ultrastructural observations on the development of Ceratomyxa aegyptiaca (Myxozoa: Bivalvulida) infecting Solea aegyptiaca (Pleuronectiformes: Soleidae) from Tunisian coastal lagoon.

Ultrastructural description of Ceratomyxa aegyptiaca Yemmen, Marton, Eszterbauer and Bahri, 2012 infecting the gallbladder of Solea aegyptiaca Chabanaud, 1927 from a tunisian north-east costal lagoon, was presented in this study. The primary cell was attached to the gallbladder epithelium and presented at one side cytoplasmic projections corresponding to pinocytotic invaginations. Netherless, early sporogonic stages development was carried with contact to the epithelial cells of gallbladder. Immature spores were identified in early sporoblasts by their valvogenic, capsulogenic and binucleated sporoplasmic cells. Capsulogenesis was asynchronous. Each capsulogenic cell presented a large condensed nucleus and a capsular primordium that extended into an external tube. The eversion and coiling of the external tube gave rise to the polar filament, which displayed six turns and an apical plug.

The life cycle of Thelohanellus kitauei (Myxozoa: Myxosporea) infecting common carp (Cyprinus carpio) involves aurantiactinomyxon in Branchiura sowerbyi.

Thelohanellus kitauei is a freshwater myxosporean parasite causing intestinal giant cystic disease of common carp. To clarify the life cycle of T. kitauei, we investigated the oligochaete populations in China and Hungary. This study confirms two distinct aurantiactinomyxon morphotypes (Aurantiactinomyxon type 1 and Aurantiactinomyxon type 2) from Branchiura sowerbyi as developmental stages of the life cycle of T. kitauei. The morphological characteristics and DNA sequences of these two types are described here. Based on 18S rDNA sequence analysis, Aurantiactinomyxon type 1 (2048 bp) and Aurantiactinomyxon type 2 (2031 bp) share 99.2-99.4 %, 99.8-100 % similarity to the published sequences of T. kitauei, respectively. The 18S rDNA sequences of these two aurantiactinomyxon morphotypes share 99.4 % similarity, suggesting intraspecific variation within the taxon, possibly due to geographic origin. Phylogenetic analyses demonstrate the two aurantiactinomyxon types clustered with T. kitauei. Regardless, based on 18S rDNA synonymy, it is likely that Aurantiactinomyxon type 1 and 2 are conspecific with T. kitauei. This is the fourth elucidated two-host life cycle of Thelohanellus species and the first record of T. kitauei in Europe.

Survivability of Kudoa septempunctata in human intestinal conditions.

To elucidate whether Kudoa septempunctata was able to live in the human intestine, we assessed viability of K. septempunctata sporoplasms under conditions that mimicked human and ragworm digestive tracts. To study the effect of osmotic pressure on viability, sporoplasms were incubated in 0.9 or 3.4 % sodium chloride solutions, which roughly corresponded to the osmotic pressure in human or ragworm tissues, respectively. While viability in 3.4 % sodium chloride did not change after 72 h, it dropped to 21 % in 0.9 % sodium chloride. To study the effect of temperature on viability, sporoplasms were incubated at 37, 15, or 25 °C, which were representative of human, winter ragworm, or summer ragworm temperatures, respectively. Viability decreased sharply to 8.4 % after 48 h at 37 °C, but remained essentially unchanged at 15 and 25 °C. In addition, sporoplasms showed strong susceptibility to bile. These results indicate that K. septempunctata could not live in the human intestine for a long time.

Ceratomyxa tunisiensis n. sp. (Myxosporea: Bivalvulida) from the Gallbladders of Two Carangid Fish Caught Off the Coast of Tunisia.

A new coelozoic Myxozoan species, Ceratomyxa tunisiensis n. sp., was found infecting the gallbladders of two carangid fish, Caranx rhonchus and Trachurus trachurus (Perciforme, Carangidae), from the Gulf of Gabès, on the southern coast of Tunisia. The parasite develops in spherical mono-, diplo-, or polysporic tropozoites in the gallbladder of the hosts. Mature spores are typical of the genus Ceratomyxa. They are transversely elongated and narrowly crescent-shaped with a slightly convex anterior and concave posterior, and measure 23 ± 0. 27 (20-25) µm width × 6 ± 0.26 (5-8) µm in length. Spore shell valves are symmetrical with rounded ends. Two spherical polar capsules situated on either side of the sutural line measure 2.2 µm (2.0-3.0) in diam. Periodical sampling of C. rhonchus and T. trachurus from Marsh 2012 to February 2013 showed that infection due to C. tunisiensis occurs in 59% and 69% of the examined fish, respectively. Molecular analysis based on the small subunit (SSU) rRNA sequence shows high genetic divergence with all other ceratomyxid species. A Maximum Likelihood phylogenetic tree shows association with the species C. leatharjecketi Fiala, kova, Kodadkova, Freeman, Bartosova-Sojkova, and Atkinson, 2015 reported from the gallbladder of Aluterusmonoceros (L.) caught in the Andaman Sea, off Malaysia. Nonetheless, the SSU rRNA sequences of C. tunisiensis and C. leatharjecketi have only a 90% similarity.

Effect of oral administration of Kudoa septempunctata genotype ST3 in adult BALB/c mice.

Kudoa septempunctata (Myxozoa: Multivalvulida) infects the muscles of olive flounder (Paralichthys olivaceus, Paralichthyidae) in the form of spores. To investigate the effect of K. septempunctata spores in mammals, adult BALB/c mice were fed with spores of K. septempunctata genotype ST3 (1.35 × 10(5) to 1.35 × 10(8) spores/mouse). After ingestion of spores, the mice remained clinically normal during the 24-h observation period. No spores were found in any tissue examined by histopathological screening. Quantitative PCR screening of the K. septempunctata 18S rDNA gene revealed that the K. septempunctata spores were detected only in the stool samples from the spore-fed groups. Collectively, these findings suggest that K. septempunctata spores are excreted in faeces and do not affect the gastrointestinal tract of adult mice.

Bipteria vetusta n. sp. ­ an old parasite in an old host: tracing the origin of myxosporean parasitism in vertebrates.

Myxosporea (Myxozoa), a group of parasitic Cnidaria, use mostly bony fishes (Teleostei) as intermediate hosts; however, they can also parasitize other vertebrates such as cartilaginous fish (Chondrichthyes). Molecular data of myxosporeans from sharks and rays (Elasmobranchii) revealed these parasites to be one of the most basal representatives in the myxosporean phylogenetic tree, suggesting their ancient evolutionary history. A new myxosporean species, Bipteria vetusta n. sp., was found in the gall bladder of rabbit fish, Chimaera monstrosa (Holocephali; Chondrichthyes), and ssrDNA-based phylogeny revealed its basal position within the marine myxosporean lineage. Molecular dating based on ssrDNA analysis suggested the origin of a stem lineage leading to the marine myxosporean lineage at the time of the origin of Chondrichthyes in the Silurian era. The two common lineages of Myxozoa, Myxosporea and Malacosporea, were estimated to have split from their common ancestor in the Cambrian era. Tracing the history of evolution of the "vertebrate host type" character in the context of molecular dating showed that cartilaginous fish represented an ancestral state for all myxosporeans. Teleosts were very likely subsequently parasitized by myxozoans four times, independently. Myxosporean radiation and diversification appear to correlate with intermediate host evolution. The first intermediate hosts of myxosporeans were cartilaginous fish. When bony fish evolved and radiated, myxosporeans switched and adapted to bony fish, and subsequently greatly diversified in this new host niche. We believe that the present study is the first attempt at molecular dating of myxozoan evolution based on an old myxosporean species ­ a living myxosporean fossil.

Interaction of Tetracapsuloides bryosalmonae, the causative agent of proliferative kidney disease, with host proteins in the kidney of Salmo trutta.

Tetracapsuloides bryosalmonae (Myxozoa) is the causative agent of proliferative kidney disease in various species of salmonids which are found in Europe and North America. Less information about the interactions of T. bryosalmonae proteins with salmonid proteins during parasite development is known. In this study, anti-T. bryosalmonae monoclonal antibody-linked to N-hydroxysuccinimide-activated spin columns were used to purify parasite and host proteins from the kidneys of infected and non-infected brown trout (Salmo trutta) Linnaeus, 1758. The samples were next analyzed by electrospray ionization coupled to mass spectrometry to identify proteins that may be involved in the infection and proliferation of T. bryosalmonae within the brown trout host. A total of 6 parasite proteins and 40 different host proteins were identified in this analysis. The identified host proteins function in various processes, which include host defense, enzymatic, and structural components. In conjunction with modern molecular based tools, such siRNA, gene replacement, or gene disruption, this data can ultimately be used to develop novel control methods for T. bryosalmonae, based on the proteins or pathways identified in this study.

Small subunit ribosomal RNA sequence links the myxospore stage of Henneguya mississippiensis n. sp. from channel catfish Ictalurus punctatus to an actinospore released by the benthic oligochaete Dero digitata.

There are more than 200 species of Henneguya described from fish. Of these, only three life cycles have been determined, identifying the actinospore and myxospore stages from their respective hosts. Two of these life cycles involve the channel catfish (Ictalurus punctatus) and the freshwater oligochaete Dero digitata. Herein, we molecularly confirm the life cycle of a previously undescribed Henneguya sp. by matching 18S ribosomal RNA (rRNA) gene sequence of the myxospore stage from channel catfish with the previously described actinospore stage (Aurantiactinomyxon mississippiensis) from D. digitata. Gill tissue from naturally infected channel catfish contained pseudocysts restricted to the apical end of the primary lamellae. Myxospores were morphologically consistent with Henneguya spp. from ictalurid fishes in North America. The spores measured 48.8 ± 4.8 µm (range = 40.7-61.6 µm) in total spore length. The lanceolate spore body was 17.1 ± 1.0 µm (14.4-19.3 µm) in length and 5.0 ± 0.3 µm (4.5-5.5 µm) in width. The two polar capsules were 6.2 ± 0.4 µm (5.8-7.0 µm) long and 5.0 ± 0.3 µm (4.5-5.5 µm) wide. The polar capsule contained eight to nine coils in the polar filament. The two caudal processes were of equal length, measuring 31.0 ± 4.1 µm (22.9-40.6 µm). The 1980-bp 18S rRNA gene sequence obtained from two excised cysts shared 99.4% similarity (100% coverage) to the published sequence of A. mississippiensis, an actinospore previously described from D. digitata. The sequence similarity between the myxospore from channel catfish and actinospore from D. digitata suggests that they are conspecific, representing alternate life stages of Henneguya mississippiensis n. sp.