The in vitro phagocytosis of Loma salmonae spores by macrophages of Atlantic salmon and two strains of chinook salmon were investigated. Opsonisation of L. salmonae with plasma factors increased uptake by head kidney macrophages. Macrophages of Atlantic salmon, which are resistant to the parasite, had a significantly higher phagocytic index (PI) than those of chinook salmon, a susceptible species. This may indicate a possible mechanism contributing to resistance in Atlantic salmon or that L. salmonae is able to evade or suppress initial binding by macrophages of chinook. Non-specific binding or lectinophagocytosis was also suggested by significantly higher PI of spores from EDTA treated plasma when compared with no plasma or heat treated plasma. In comparison, uptake of Baker's yeast Saccharomyces cerevisiae by phagocytes was not significantly different between fish species and strains for all treatments.

The microsporidian Loma salmonae (Putz, Hoffman & Dunbar, 1965) Morrison & Sprague, 1981 has caused significant gill disease in Pacific salmon Oncorhynchus spp. Host specificity of the parasite was examined experimentally by per os challenge of selected salmonids and non-salmonids with infective chinook salmon O. tshawytscha gill material. Pink Oncorhynchus gorbuscha and chum salmon O. keta, brown Salmo trutta and brook trout Salvelinus fontinalis, and chinook salmon (controls) were positive, whereas Atlantic salmon Salmo salar and Arctic char Salvelinus alpinus were negative. In addition, no non-salmonids were susceptible to experimental exposure. Wild Pacific salmon species in British Columbia, Canada, were examined for L. salmonae during their freshwater life history stages (smolts, prespawning, spawning). All stages were infected, although infections in smolts were only detectable using a L. salmonae-specific PCR test. Many previous Loma spp. described from Oncorhychus spp. are likely L. salmonae based on host, parasite morphology, and site of infection.

Loma salmonae (Putz, Hoffman and Dunbar, 1965) Morrison & Sprague, 1981 (Microsporidia) is an important gill pathogen of Pacific salmon Oncorhynchus spp. in the Pacific Northwest. Three strains of chinook salmon O. tshawytscha were infected in 2 trials with L. salmonae by feeding of macerated infected gill tissue or per os as a gill tissue slurry. Intensity of infection was significantly higher in the Northern stream (NS) strain as compared to the Southern coastal (SC) and a hybrid (H) strain derived from these 2 strains. Both wet mount and histological enumeration of intensity of infection demonstrated strain differences. Survival in the NS strain was significantly lower than the other strains. The NS strain may represent a naive strain and be less able to mount an effective immune response against the parasite.

Journal of Fish DiseasesVolume 22, Issue 4 p. 311-313 Iodophor treatment is not completely efficacious in preventing Loma salmonae (Microsporidia) transmission in experimentally challenged chinook salmon, Oncorhynchus tshawytscha (Walbaum) R. W. Shaw, R. W. Shaw Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada Department of Fisheries and Oceans, Pacific Biological Station, Nanaimo, British Columbia, CanadaSearch for more papers by this authorM. L. Kent, M. L. Kent Department of Fisheries and Oceans, Pacific Biological Station, Nanaimo, British Columbia, CanadaSearch for more papers by this authorM. L. Adamson, M. L. Adamson Department of Zoology, University of British Columbia, Vancouver, British Columbia, CanadaSearch for more papers by this author R. W. Shaw, R. W. Shaw Department of Zoology, University of British Columbia, Vancouver, British Columbia, Canada Department of Fisheries and Oceans, Pacific Biological Station, Nanaimo, British Columbia, CanadaSearch for more papers by this authorM. L. Kent, M. L. Kent Department of Fisheries and Oceans, Pacific Biological Station, Nanaimo, British Columbia, CanadaSearch for more papers by this authorM. L. Adamson, M. L. Adamson Department of Zoology, University of British Columbia, Vancouver, British Columbia, CanadaSearch for more papers by this author First published: 18 January 2002 https://doi.org/10.1046/j.1365-2761.1999.00167.xCitations: 16 Ross W Shaw, 3190 Hammond Bay Road, Pacific Biological Station, Nanaimo, BC, Canada V9R 5K6 AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat Citing Literature Volume22, Issue4July 1999Pages 311-313 RelatedInformation

Loma salmonae (Putz, Hoffman and Dunbar, 1965) Morrison and Sprague, 1981 (Microsporidia) causes prominent gill disease in pen-reared chinook salmon Oncorhynchus tshawytscha in the Pacific Northwest. Transmission of the parasite was examined by exposing Pacific salmon Oncorhynchus spp. to infectious spores by various routes: per os, intraperitoneal, intramuscular, and intravascular injection, by cohabitation with infected fish, and by placement of spores directly on the gill. All exposure methods led to infections except placement of spores on the gill. Putative sporoplasms were visible in epithelial cells of the alimentary canal within 24 h of per os exposure. L. salmonae may initially infect alimentary epithelial cells and then migrate into the lamina propia to access the blood stream. Positive results obtained by intravascular injection suggest that autoinfection from spores of ruptured xenomas in the endothelium may also occur. The cohabitation experiment demonstrates that fish may become infected by spores released from live fish.

Loma embiotocia n. sp. is described from the gills of shiner perch (Cymatogaster aggregata) from waters off Vancouver Island, British Columbia, Canada. Highest prevalence at a site was 15% and greatest intensity was 583 xenomas per fish. Xenomas averaged 0.13 mm in diameter (0.06-0.16 mm) and contained ovoid spores 4.8 x 2.6 (4.0-5.0 x 2.0-3.0) microns. Sporogonic stages were dispersed throughout the xenomas. The xenoma wall was smooth lacking invaginations into the cyto plasm: sporoblasts were not highly vacuolated, and the sporophorous vesicle formed before sporogony. In addition to differences in host and geographic location the new species is distinguished from Loma salmonae, the only other species in the genus known from British Columbia, by its internal transcribed spacer (ITS) ribosomal DNA sequence.

The myxosporean parasite Kudoa thyrsites is reported from a new host, Aulorhynchus flavidus, the tube-snout, collected near Vancouver, British Columbia, Canada. Prevalence reached 100% and intensity 1,535 pseudocysts per 2 cm length of fish. Polymerase chain reaction primers specific for K. thyrsites amplified a fragment of the small subunit rDNA and confirmed identification. These primers also allowed detection of K. thyrsites in young (< 4-mo-old) fish with no other apparent sign of infection. No inflammatory response or liquefaction of host tissue was associated with the infection. The number of pseudocysts per infected fish was not correlated with fish size or condition, although larger fish (total length) had larger pseudocysts (rs = 0.437, P < 0.001). This finding brings to 28 the number of potential hosts for the species. Kudoa thyrsites is a well recognized cause of soft flesh in netpen-reared Atlantic salmon in coastal waters of British Columbia. Tube-snouts are common in and around these netpens, and thus may be a significant host reservoir for K. thyrsites.