Loma Salmonae Research Articles

Loma salmonae

This datasheet on Loma salmonae covers Identity, Distribution, Hosts/Species Affected.

Retrospective study of the prevalence of Pseudoloma neurophilia shows male sex bias in zebrafish Danio rerio (Hamilton-Buchanan).

Retrospective study of the prevalence of Pseudoloma neurophilia shows male sex bias in zebrafish Danio rerio (Hamilton-Buchanan).

Development of the microsporidian parasite, Loma salmonae, in a rainbow trout gill epithelial cell line (RTG-1): evidence of xenoma development in vitro.

Growth and propagation of fish-infecting microsporidians within cell culture has been more difficult to achieve than for insect- and human-infecting microsporidians. Fish microsporidia tend to elicit xenoma development rather than diffuse growth in vivo, and this process likely increases host specificity. We present evidence that the fish microsporidian, Loma salmonae, has the capacity to develop xenomas within a rainbow trout gill epithelial cell line (RTG-1). Spore numbers increased over a 4 weeks period within cell culture flasks. Xenoma-like structures were observed using phase contrast microscopy, and then confirmed using transmission electron microscopy. Optimization of the L. salmonae-RTG-1 cell model has important implications in elucidating the process of xenoma development induced by microsporidian parasites.

Immunohistochemical localization of inflammatory cells and cell cycle proteins in the gills of Loma salmonae infected rainbow trout (Oncorhynchus mykiss)

Microsporidial gill diseases particularly those caused by Loma salmonae incur significant economic losses to the salmonid aquaculture industry. The gill responses to infection include the formation of xenomas and the acute hyperplastic inflammatory responses once the xenomas rupture releasing infective spores. The aim of this work was to characterize the inflammatory responses of the gill to both the presence of the xenomas as well as the hyperplasia associated with L. salmonae infection in the rainbow trout gill following an experimental infection using immunohistochemistry. Hyperplastic lesions demonstrated numerous cells expressing PCNA as well as an apparent increased expression of caspase-3 and number of apoptotic cells (TUNEL positive cells). There was an expression of TNFα in individual cells within the gill and increased expression of a myeloid cell line antigen indicating the presence of granulocyte infiltration of both the hyperplastic lesions as well as the xenomas. Similar immune-reactivity was seen in gill EGCs. Hyperplastic gill lesions showed a marked infiltration of CD8+ cells and expression of MHC class I antigens. These findings suggest that L. salmonae xenomas may be subject to infiltration by the host immune cells as well as the mounting or a marked cellular cytotoxic immunoreaction in the resultant hyperplasia following xenoma rupture and spore release.

IgY Technology in aquaculture – a review

AbstractSince the discovery of IgY in egg yolk in late 1800s, many applications of this antibody in diagnostics and therapeutics have been reported in human and veterinary medicine. The mass use of antimicrobial agents in aquaculture has caused the resistance in certain bacteria, and these fish pathogens cause tremendous economic losses in aquaculture industry coupled with antibiotic resistance, consequently causing barriers in international trades. IgY antibodies have been developed for the treatment and prevention of certain fish diseases such as white spot syndrome in shrimp, vibriosis, enteric redmouth disease and edwardsiellosis. These antibodies are also developed for the recognition of developing and mature stages of Loma salmonae (microsporidia) in the farmed pacific salmon. Other uses of IgY in aquaculture include the development of sandwich ELISA for the detection of ciguatoxin (a poisonous organic compound) in the tissues of fish, and recently, potential sea food persevering properties of IgY have been revealed. Our review presents an analysis of the characteristics, extraction methods, therapeutic, detection, and seafood‐persevering applications of IgY antibodies in aquaculture.

Impact and control of protozoan parasites in maricultured fishes

Aquaculture, including both freshwater and marine production, has on a world scale exhibited one of the highest growth rates within animal protein production during recent decades and is expected to expand further at the same rate within the next 10 years. Control of diseases is one of the most prominent challenges if this production goal is to be reached. Apart from viral, bacterial, fungal and metazoan infections it has been documented that protozoan parasites affect health and welfare and thereby production of fish in marine aquaculture. Representatives within the main protozoan groups such as amoebae, dinoflagellates, kinetoplastid flagellates, diplomonadid flagellates, apicomplexans, microsporidians and ciliates have been shown to cause severe morbidity and mortality among farmed fish. Well studied examples are Neoparamoeba perurans, Amyloodinium ocellatum, Spironucleus salmonicida, Ichthyobodo necator, Cryptobia salmositica, Loma salmonae, Cryptocaryon irritans, Miamiensis avidus and Trichodina jadranica. The present report provides details on the parasites' biology and impact on productivity and evaluates tools for diagnosis, control and management. Special emphasis is placed on antiprotozoan immune responses in fish and a strategy for development of vaccines is presented.

Retention of viable microsporidial (Loma salmonae) spores within the blue mussel (Mytilus edulis): Use of an experimental laboratory model probing pathogen transfer within a multi-trophic aquaculture setting

An in vivo rainbow trout (Oncorhynchus mykiss) branchial xenoma expression model was used to detect the presence of viable microsporidial spores (Loma salmonae) within aquarium-held blue mussels (Mytilus edulis) experimentally exposed to a suspension of semi-purified L. salmonae spores. In two separate studies, viscera from mussels exposed to spores for 4hr were fed to trout that subsequently developed xenomas within their gills 6weeks post-infection. The results from these studies provide proof of principle evidence that L. salmonae spores are captured from the water column by mussels, and remain viable within mussel tissue. However, mussel-fed fish yielded significantly fewer xenomas compared to reference fish exposed to an intraperitoneal injection of spores. A spore-transfer efficiency value was calculated (xenomas/spore dose) and revealed 0.03% of spores led to xenomas in IP injected fish, while 0.005% of spores exposed to mussels yielded xenomas in viscera-fed fish. Relative spore-transfer efficiency provided by mussel filtration and IP injection is therefore 16.6%. In a separate trial, we examined the influence of time, after mussels ingest spores for 4hr, on xenoma development in trout. While 75% of fish became infected after 4hr of exposure (similar to previous trials), only 10% became infected after 7days, which indicates that blue mussels may act as a reservoir for infectious L. salmonae spores for at least 7days. In a final pilot study, we aimed to determine whether the addition of mussels to L. salmonae contaminated water provides bioremediation. The percentage of trout that became infected was similar in fish exposed to contaminated water versus those exposed to contaminated water filtered by mussels. Interestingly, trout exposed to water filtered by mussels, developed higher mean xenoma counts which suggests that viable spores are expelled via mussel feces and pseudofeces, which can then be consumed by trout.

Luna stain, an improved selective stain for detection of microsporidian spores in histologic sections

Microsporidia in histologic sections are most often diagnosed by observing spores in host tissues. Spores are easy to identify if they occur in large aggregates or xenomas when sections are stained with hematoxylin and eosin (H&E). However, individual spores are not frequently detected in host tissues with conventional H&E staining, particularly if spores are scattered within the tissues, areas of inflammation, or small spores in nuclei (i.e. Nucleospora salmonis). Hence, a variety of selective stains that enhance visualization of spores is recommended. We discovered that the Luna stain, used to highlight eosinophils, red blood cells, and chitin in arthropods and other invertebrates, also stains spores of Pseudoloma neurophilia. We compared this stain to the Gram, Fite's acid fast, Giemsa, and H&E stains on 8 aquatic microsporidian organisms that were readily available in our 2 laboratories: Loma salmonae, Glugea anomala, Pseudoloma neurophilia, Pleistophora hyphessobryconis, Pleistophora vermiformis, Glugea sp., Steinhausia mytilovum, and an unidentified microsporidian from UK mitten crabs Eriocheir sinensis. Based on tinctorial properties and background staining, the Luna stain performed better for detection of 6 of the 8 microsporidia. Gram stain was superior for the 2 microsporidia from invertebrates: S. mytilovum and the unidentified microsporidian from E. sinensis.

Pilot Study Demonstrating that Immunostimulation with β glucan Fails to Moderate the Immunosuppressive Effects of Dexamethasone when Co-administered to Rainbow Trout Oncorhynchus mykiss Experimentally Challenged with the Microsporidian Loma salmonae

In this pilot study, juvenile rainbow trout were experimentally challenged with the microsporidian Loma salmonae to determine the effects of immunostimulation with β-1,3/1,6 glucan administered in the feed at 200 mg/kg of feed, and immunosuppression with dexamethasone at 300 mg/kg of feed when these were administered in the early stages of infection. Six weeks after oral exposure to Loma spores, control fish developed a mean of 34.8 spore filled xenomas per gill arch; those which had received β glucan had significantly fewer xenomas (23.6) whereas those receiving dexamethasone had significantly more (43.0). Paradoxically, when fish received both β glucan and dexamethasone in any of three temporal combinations, xenoma numbers were significantly higher (51.0-65.1) even when compared to fish receiving only dexamethasone.

Resistance to Loma salmonae in Rainbow Trout Oncorhynchus mykiss Subsequent to Recovery from an Initial Low-dose Cohabitation Exposure

Resistance to Loma salmonae in Rainbow Trout Oncorhynchus mykiss Subsequent to Recovery from an Initial Low-dose Cohabitation Exposure

Low genetic variation in the salmon and trout parasite Loma salmonae (Microsporidia) supports marine transmission and clarifies species boundaries

Loma salmonae is a microsporidian parasite prevalent in wild and farmed salmon species of the genus Oncorhynchus. This study compared ribosomal RNA (rDNA) and elongation factor-1 alpha (EF-1alpha) gene sequences to look for variation that may provide a basis for distinguishing populations. Specimens were collected from laboratory, captive (sea netpen farm and freshwater hatchery) and wild populations of fish. The host range included rainbow trout O. mykiss, Pacific salmon Oncorhynchus spp. and brook trout Salvelinus fontinalis from British Columbia, Prince Edward Island, Canada, from California, Colorado, Idaho, U.S.A. and from Chile. Both loci suggested that a variant in S. fontinalis (named 'SV') was a separate species. This was supported by the absence of similar variants in the source material (isolated from laboratory-held O. tshawytscha) and high divergence (1.4 to 2.3% in the rDNA and EF-1alpha) from L. salmonae in the type host and locality (0. mykiss in California). L. salmonae from freshwater and anadromous Oncorhynchus spp. were distinguished, providing a basis on which to evaluate possible sources of infection and suggesting geographic boundaries are important. Higher genetic variation occurred among samples of freshwater origin and from a sea netpen farm in Chile, suggesting these environments may present greater population diversity. Invariance in rDNA sequence across 17 samples from anadromous salmon in rivers, lakes, ocean, farms and hatcheries supports the hypothesis that marine transmission occurs and effectively prevents population substructuring caused by freshwater transmission.

Efficacy of Intraperitoneally and Orally Administered ProVale, a Yeast β‐(1,3)/(1,6)‐D‐glucan Product, in Inhibiting Xenoma Formation by the Microsporidian Loma salmonae on Rainbow Trout Gills

AbstractThe objectives of the research were to compare the efficacy of ProVale yeast beta‐glucan (β‐glucan) with that of a previously tested research‐grade yeast β‐glucan preparation when administered as an intraperitoneal (IP) injection and to also pilot test the effectiveness of ProVale yeast β‐glucan as a feed additive for reducing Loma salmonae xenoma formation on the gills of rainbow trout Oncorhynchus mykiss. Rainbow trout received IP injections of ProVale (4, 10, or 20 mg of ProVale/kg of fish) or Sigma β‐glucan (4 mg/kg). Oral challenge with L. salmonae occurred 1 week after IP injection with the β‐glucan products. For the second objective, 400 rainbow trout were separated into tanks and duplicate groups were treated with 0, 50, 100, and 200 g of ProVale/1,000 kg of feed. Starting at 3 weeks prior to challenge and continuing 2 weeks after challenge, rainbow trout were fed the various ProVale doses daily at a feeding rate of 1% of the fish biomass. Commencing at 4 weeks postchallenge, the fish in each trial were evaluated for the presence of xenomas on the first left gill arch. The most protective IP dose of commercial ProVale was 10 mg/kg when compared with the laboratory‐grade IP dose of Sigma β‐glucan (4 mg/kg). Both of these intraperitoneally administered β‐glucan products were effective in reducing the mean xenoma count. ProVale used as a feed coating (200 g/1,000 kg) was able to reduce the mean xenoma count by 50%.

Selected parasitosis in cultured and wild fish

While intensive aquaculture has and will continue to supply the ever growing population with highly nutritious protein, it also comes with problems which include more frequent outbreaks of diseases in fish farms and transmission of diseases between farmed and wild fish. We have selected four Phyla of economically important fish parasites for our present discussion—a haemoflagellate ( Cryptobia salmositica), a microsporidian, ( Loma salmonae) , a monogenean ( Gyrodactylus salaries) and two copepods ( Lepeophtheirus salmonis, Caligus rogercresseyi). This review consists of two parts with a brief description of each parasite and its biology related to transmission, followed by discussions on epizootic outbreaks in both wild and farmed fish, interactions between wild and farmed fish, and disease prevention and control.

Effects of dexamethasone on host innate and adaptive immune responses and parasite development in rainbow trout Oncorhynchus mykiss infected with Loma salmonae

The effects of dexamethasone (dex) treatment on infections with the microsporidian parasite, Loma salmonae and the effects of dex on initiation of the adaptive immune response were investigated in rainbow trout, Oncorhynchus mykiss experimentally infected with the parasite. Dex treatment resulted in significantly higher infections with the parasite in the gills and other internal organs, suggesting that dex inhibits aspects of the innate immune response to L. salmonae; the heavier infections in the gills and organs of rainbow trout resembled infections seen in Chinook salmon. Mean xenoma counts per microscope field in the gills of fish infected with L. salmonae treated with dex or left untreated were 169 and 30, respectively. Although higher numbers of xenomas were observed in dex treated fish, the xenomas were generally smaller in size than in infected control fish. The xenomas in dex treated fish showed morphological signs of degeneration including loss and degeneration of early parasite stages, accumulation of amorphous material in xenomas, and infiltration with phagocytic cells containing degenerated parasites. The xenomas in infected untreated fish had larger xenomas with a more uniform size and contained identifiable parasite stages in the cytoplasm. According to this study, once fish have developed an adaptive immune response to the parasite by previous exposure, then fish have 100% protection to reinfection even when treated with heavy doses of dex. L. salmonae immune fish treated or untreated with dex during reinfection with the parasite developed no xenomas in the gills 6 weeks post reinfection. These results indicate that once the cellular response is primed to L. salmonae, then dex related immunosuppression does not reduce the effectiveness of the adaptive immune response.

Chicken-derived IgY recognizes developing and mature stages of Loma salmonae (Microsporidia) in Pacific salmon, Oncorhynchus spp.

A polyclonal IgY preparation, purified from yolk of immunized hens, is shown to be useful for the detection of Loma salmonae in Pacific salmon. Purity of the IgY was confirmed by SDS-PAGE and western blots of yolk protein extracts. Reactivity of the IgY preparation to L. salmonae was determined through indirect-fluorescent antibody tests on purified spores and by immunohistochemistry. Developing xenomas in histological sections of heart and gill tissue of infected chinook salmon (Oncorhynchus tshawytscha) were visualized as early as 4 weeks post-exposure (PE). Non-lethal detection of L. salmonae was obtained by indirect-fluorescent microscopy of acetone-fixed gill smears. The IgY preparation was shown to react with another Loma sp., L. branchialis. In contrast, no reactivity was observed with other microsporidian parasites of fish such as Pseudoloma neurophilia and Glugea anomala. Yolk derived IgY may be useful in the detection of other fish pathogens.

Development of an Effective Whole-Spore Vaccine To Protect against Microsporidial Gill Disease in Rainbow Trout (Oncorhynchus mykiss) by Using a Low-Virulence Strain ofLoma salmonae

In determining the effective vaccine spore dose of a low-virulence strain of Loma salmonae to limit microsporidial gill disease in trout, we found that fish receiving 10(3) to 10(5) killed spores had the best protection against experimental infection, with 85% fewer xenomas in their gills than in the controls. Intraperitoneal delivery of the vaccine was effective, and the addition of adjuvant did not improve vaccine performance against this disease-causing microsporidian.

Transmission of the microsporidian gill parasite, Loma salmonae

Since it was first reported in 1987 at a hatchery in British Columbia, Loma salmonae has become increasingly important as an emerging parasite affecting the Canadian salmonid aquaculture industry. L. salmonae causes Microsporidial Gill Disease of Salmon (MGDS) in farmed Pacific salmonids, Oncorhynchus spp., resulting in respiratory distress, secondary infections and high mortality rates. In the last decade, laboratory studies have identified key transmission factors for this disease and described the pathogenesis of MGDS. L. salmonae enters the host via the gut, where it injects sporoplasm into a host cell, which then migrates to the heart for a two-week merogony-like phase, followed by a macrophage-mediated transport of the parasite to the gill, with a final development stage of a spore-laden xenoma within the endothelial and pillar cells. Xenoma rupture triggers a cascade of inflammatory events leading to severe, persistent, and extensive proliferative branchitis. The development of robust and reliable experimental challenge models using several exposure methods in marine and freshwater environments with several fish hosts, is a primary reason for the success of scientific research surrounding L. salmonae. To date, demonstrated factors affecting MGDS transmission include host species, strain and size, the length of contact time between naïve and infected fish, water temperature and flow rates.

Timing of intraperitoneal administration of β‐1,3/1,6 glucan to rainbow trout, Oncorhynchus mykiss (Walbaum), affects protection against the microsporidian Loma salmonae

Timing of intraperitoneal administration of <i>β</i>‐1,3/1,6 glucan to rainbow trout, <i>Oncorhynchus mykiss</i> (Walbaum), affects protection against the microsporidian <i>Loma salmonae</i>

A NEW PARVICAPSULID (MYXOSPOREA) SPECIES IN ADULT PINK SALMON, ONCORHYNCHUS GORBUSCHA, FROM THE QUINSAM RIVER, BRITISH COLUMBIA, CANADA

Myxospores consistent with species of Parvicapsula were observed in kidney of 15 of 95 (15.8%) adult pink salmon, Oncorhynchus gorbuscha, collected from the Quinsam River, British Columbia, Canada. The spores were elongate and curved with unequal valves, and 2 spherical-to-subspherical polar capsules within a highly refractile capsular region. The spores were unlike those of P. minibicornis found in nearby populations of Pacific salmon, Oncorhynchus spp. The spore dimensions were similar to those of Parvicapsula pseudobranchicola from Atlantic salmon, Salmo salar, in Norway, and the spores seemed similar to an undescribed Parvicapsula sp. from several Oncorhynchus spp. in Puget Sound, Washington. A sequence of 1,480 base pairs (bp) of the small subunit ribosomal RNA gene (SSU rDNA) of the parasite from pink salmon was most similar to, but distinct from, that of other Parvicapsula spp. The parasite is described as a new species, Parvicapsula kabatai n. sp. Polymerase chain reactions amplified a 158-bp sequence, unique to P. kabatai n. sp., from 22 of 93 (23.7%) adult pink salmon kidney samples, from 3 of 3 juvenile pink salmon collected in the ocean 125 km north of the Quinsam River, and from 2 of 5 archival coho salmon, Oncorhynchus kisutch, samples from Puget Sound. The parasite occurs within the lumen and epithelium of renal tubules and ducts, and within the renal interstitium. Concurrent infections with extrasporogonic stages of the myxosporean CKX, the microsporidian Loma salmonae, and a Myxidium sp. also were observed in the adult pink salmon.

Whole body net ion fluxes, plasma electrolyte concentrations and haematology during a Loma salmonae infection in juvenile rainbow trout, Oncorhynchus mykiss (Walbaum)

Loma salmonae infections of salmonids culminate in the development of branchial xenomas and subsequent focal hyperplasia of the lamellar or filament epithelium following xenoma rupture and spore release. The effects of this acute branchial disruption upon net ionic flux rates and plasma electrolyte concentrations were determined in juvenile rainbow trout given an experimental oral exposure to L. salmonae. Mean numbers of branchial xenomas peaked at week 5 post-exposure (PE), which coincided with a reduction in the specific growth rate, although there were no significant differences in mass, length or condition of Loma-exposed fish compared with unexposed controls. Following exposure, negative net whole body Na(+) and K(+) fluxes decreased, whereas net Cl(-) fluxes remained unchanged compared with non-exposed control fish. At week 3 PE during the initial branchial xenoma formation stage, there was a significant negative whole body net K(+) flux in Loma-exposed trout compared with other points during the exposure and subsequent infection. Additionally, Loma-exposed fish had marginally elevated plasma Na(+) and Cl(-) concentrations, whilst K(+) levels remained unchanged, compared with control fish. Although there was a progressive decrease in leucocrit, haematocrit remained unchanged over the course of the Loma exposure and subsequent infection. These results suggest that ionic compensation can occur at the gills during the development of xenomas during exposure to L. salmonae and the resultant infection, therefore allowing defence of plasma electrolyte concentrations, unlike the acute ionic disturbances seen with some other parasitic diseases.