Viability of Loma salmonae (Microsporidia) under laboratory conditions

Shaw, R. W.; Kent, Michael L.; Adamson, Martin L.

doi:10.1007/pl00008529

Cited by 21 publications

(17 citation statements)

References 13 publications

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“…Two seawater transmission modes are likely, given the path of transmission through the gut (Shaw et al 1998): inter-and intraspecific piscivory among young salmon (or feeding on tissues from dead fish) in coastal near-shore habitats prior to seaward migrations and seawater transmission by ingestion of free spores (Kent et al 1989(Kent et al , 1995. The latter mode is supported by evidence suggesting spores can be viable in seawater for up to a year (Shaw et al 2000b). Another, possibility is that the low overall genetic variation in L. salmonae could be the result of recent translocation of this parasite.…”

Section: Brown Et Al: Genetic Variation In Loma Salmonaesupporting

confidence: 56%

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

Brown

Kent²,

Adamson³

2010

Dis. Aquat. Org.

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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-1α) 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, USA 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-1α) from L. salmonae in the type host and locality (O. 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.KEY WORDS: Loma salmonae · Microsporidia · Oncorhynchus · Pacific salmon · Salmon farm · Salvelinus fontinalis · rDNA · EF-1 α Resale or republication not permitted without written consent of the publisherDis Aquat Org 91: [35][36][37][38][39][40][41][42][43][44][45][46] 2010 since the recent development of a vaccine against L. salmonae . Non-genetic studies have suggested there may be strains that differ in host preference (e.g. preferring coho and Chinook salmon to brook or rainbow trout) or showing different infection patterns in salmon versus trout (Bader et al. 1998, Shaw et al. 2000a,c, Sánchez et al. 2001b, Ramsay et al. 2002, Lovy et al. 2004, Kent & Speare 2005.The present study examined genetic variation across Loma salmonae from the wild, hatcheries, sea netpen farms and laboratories in British Columbia (BC) and Prince Edward Island (PEI), Canada, in California, Colorado, and Idaho, USA, and in Chile to establish the baseline level of variation that we might expect within this species and to look for genetic variants that may correspond to different populations. Genetic data from the type host, rainbow trout Oncorhynchus mykiss in California, is essential as this parasite species is morphologically indistinguishable across its geographic and host range (Morrison & Sprague 1983, Shaw et al. 1997, Brown & Kent 2002 and distinct strains or cryptic species may exist. For example, some data suggest L. salmonae...

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Section: Brown Et Al: Genetic Variation In Loma Salmonaesupporting

confidence: 56%

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

Brown

Kent²,

Adamson³

2010

Dis. Aquat. Org.

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“…showed that spores of Loma salmonae could survive at 150 ppm iodine for 25 min, a dose typically used for disinfecting salmon eggs. The efficacy of chlorine and other disinfectants to kill microsporidia have been evaluated using direct exposure to animals , Khalifa et al 2001, Johnson et al 2003, infectivity of cell cultures (Wolk et al 2000and papers cited therein, Santillana-Hayat et al 2002, John et al 2003, Leiro et al 2004, Jordan 2005, Li & Fayer 2006, viability of spores detected by polar tube extrusion (He et al 1996, Keohane & Weiss 1999 and papers cited therein, Shaw et al 2001), or with stains that demonstrate either live or dead spores (Green et al 2000, Hoffman et al 2003. Green et al (2000) developed a method for evaluating viability of Encephalitozoon cuniculi using SYTOX Green in conjunction with Calcofluor White M2R™.…”

Section: Discussionmentioning

confidence: 99%

Spores of two fish microsporidia (Pseudoloma neurophilia and Glugea anomala) are highly resistant to chlorine

Ferguson¹,

Watral²,

Schwindt³

et al. 2007

Dis. Aquat. Org.

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Pseudoloma neurophilia (Microsporidia) is the most common pathogen found in zebrafish Danio rerio research facilities. The parasite is associated with marked emaciation. Zebrafish laboratories usually disinfect eggs to prevent transmission of pathogens, typically with chlorine at 25 to 50 ppm for 10 min. The ability of chlorine to kill spores of P. neurophilia and 2 other microsporidia, Glugea anomala and Encephalitozoon cuniculi, was evaluated using 2 viability stains. SYTOX ® Green was used to visualize dead spores, and live spores were identified by their ability to extrude polar tubes in Fungi-Fluor™ solution following UV exposure. Results with both stains were similar at various chlorine concentrations for P. neurophilia and G. anomala, but Fungi-Fluor was not useful for E. cuniculi, due to the much smaller spore size. Using the SYTOX stain, we found that 5 ppm chlorine for 10 min causes 100% death in spores of E. cuniculi, which was similar to findings in other studies. In contrast, the spores of P. neurophilia and G. anomala were much more resistant to chlorine, requiring >100 or 1500 ppm chlorine, respectively, to achieve > 95% spore death. Repeating chlorine exposures with spores of P. neurophilia using solutions adjusted to pH 7 increased the efficacy of 100 ppm chlorine, achieving > 99% spore inactivation. We corroborated our viability staining results with experimental exposures of zebrafish fry, achieving heavy infections in fry at 5 to 7 d postexposure in fish fed spores treated at 50 ppm (pH 9). Some fish still became infected with spores exposed to 100 ppm chlorine (pH 9.5). This study demonstrates that spores of certain fish microsporidia are highly resistant to chlorine, and indicates that the egg disinfection protocols presently used by most zebrafish research facilities will not prevent transmission of P. neurophilia to progeny.KEY WORDS: SYTOX Green · Fungi-Fluor · Pseudoloma neurophilia · Glugea anomala · Encephalitozoon cuniculi · Chlorine toxicity · Viability staining Resale or republication not permitted without written consent of the publisher

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“…Recently, it has also been shown that temperature regulates the rate of clearance of xenomas (Becker and Speare 2004b), which provides an interesting avenue through which to explore non-pharmacological methods of treatment. Shaw et al (2000b) investigated the viability of L. salmonae spores under laboratory conditions by polar filament extrusion and infectivity to Chinook salmon. Extrusion rates of isolated spores decreased from about 50% to zero by 100 d after storage in freshwater or seawater at 4°C.…”

Section: Temperature Effectsmentioning

confidence: 99%

“…References to details of experimental methods are cited below. In general, the sequelae of infection are similar with both hosts, except that Chinook are more susceptible (Shaw et al 2000b, Ramsay et al 2002 and they remain infected longer .…”

mentioning

confidence: 93%

“…The infection is prevalent in wild and captive populations of salmon and trout (Wales and Wolf 1955, Bekhti and Bouix 1985, Shaw et al 2000b, and disease associated with the infection has been reported in both freshwater (Markey et al 1994, Bruno et al 1995, Bader et al 1998) and seawater (Speare et al 1989, Kent et al 1989, Kent and Poppe 1998. Most infections are reported from rainbow trout (Oncorhynchus mykiss) (Walbaum) and Chinook salmon (Oncorhynchus tshawytscha) (Walbaum), and our understanding of the development of the parasites is based mainly on laboratory studies with these species.…”

mentioning

confidence: 99%

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Review of the sequential development of Loma salmonae (Microsporidia) based on experimental infections of rainbow trout (Oncorhynchus mykiss) and Chinook salmon (O. tshawytscha)

Kent¹,

Speare²

2005

FOLIA PARASIT

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Abstract. Loma salmonae (Putz, Hoffman et Dunbar, 1965) is a common gill parasite of salmonids, and essentially all species in the genus Oncorhynchus are susceptible. Infections occur in both fresh and salt water. Loma salmonae is directly transmissible by ingestion of spores or infected tissue. The parasite infects the wall of blood vessels of various organs, but the gill is the primary site of infection. Initial infection occurs in the intestine, and xenomas are easily detected in the gills by standard histology at 4-6 wk post-exposure. A few presporogonic stages of the parasite are found in the heart endothelium prior to xenoma formation in the gills. Ultrastructure studies of early infections demonstrated that wandering blood cells transport the meronts to the gills, and that merogony occurs in pillar cells and other cells underlying the gill endothelium. Xenomas develop in these cells, resulting in hypertrophied host cells filled with spores. Xenomas ultimately rupture, and are associated with severe inflammation in which free spores are found in macrophages. The parasites are most pathogenic during this phase of the infection, resulting in severe vasculitis and clinical disease. Both rainbow trout (Oncorhynchus mykiss) and Chinook salmon (Oncorhynchus tshawytscha) recover from infections, but free spores persist in kidney and spleen phagocytes for many months after xenomas are absent in Chinook salmon. Fish that have recovered from the infection show strong immunity against the parasite, lasting up to 1 year. Fish are susceptible to infection by other routes of exposure by spores; co-habitation, anal gavage, and intramuscular, intraperitoneal and intravascular injection. Autoinfection probably occurs following release of spores in blood vessels after xenomas rupture. The optimal temperature for L. salmonae infections is 15-17°C, with a permissive range of 11-20°C.

show abstract

Viability of Loma salmonae (Microsporidia) under laboratory conditions

Cited by 21 publications

References 13 publications

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

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

Spores of two fish microsporidia (Pseudoloma neurophilia and Glugea anomala) are highly resistant to chlorine

Review of the sequential development of Loma salmonae (Microsporidia) based on experimental infections of rainbow trout (Oncorhynchus mykiss) and Chinook salmon (O. tshawytscha)

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