Methemoglobin concentrations in three salmonid species following exposure to benzocaine or tricaine methanesulfonate.

Methemoglobin is hemoglobin containing ferric iron rather than ferrous iron which renders it incapable of binding to oxygen. Blood sampling of fish is done under sedation or general anesthesia. Tricaine methanesulfonate (TMS) or benzocaine is commonly used but both can cause oxidation of hemoglobin to methemoglobin.

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).

The effects of temperature and body size on immunological development and responsiveness in juvenile shortnose sturgeon (Acipenser brevirostrum).

Sturgeon are an important evolutionary taxa of which little is known regarding their responses to environmental factors. Water temperature strongly influences growth in fish; however, its effect on sturgeon immune responses is unknown. The objective of this study was to assess how 2 different temperatures affect immune responses in shortnose sturgeon (Acipenser brevirostrum) relevant immune organs such as the meningeal myeloid tissue, spleen, thymus and skin.

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.

Demonstrated efficacy of a pilot heterologous whole-spore vaccine against Microsporidial gill disease in rainbow trout.

Intraperitoneal vaccines using whole viable spores of the microsporidian Glugea anomala or Glugea hertwigi reduced the numbers of branchial xenomas by 80% and 91%, respectively, after a standard experimental infection of juvenile rainbow trout with the microsporidian Loma salmonae. Similar significant results were obtained when killed-spore preparations were used.

Comparison of NADH-dependent cytochrome b5 reductase activity and in vitro methemoglobin induction by sodium nitrite in Oncorhynchus mykiss, Salmo salar, and Salvelinus fontinalis.

Methemoglobin is hemoglobin containing ferric iron. Methemoglobin cannot bind to oxygen and at high concentrations causes tissue hypoxia. Brook trout (Salvelinus fontinalis) develop significantly greater methemoglobinemia than Atlantic salmon (Salmo salar) or rainbow trout (Oncorhynchus mykiss) following general anesthesia with benzocaine or tricaine methanesulfonate.

Evaluation of co-oximetry for the measurement of methemoglobin in rainbow trout (Oncorhynchus mykiss) and values in 3 salmonid species.

Background: Methemoglobin (metHb) is oxidized hemoglobin that cannot reversibly bind oxygen, and concentrations in healthy fish have been reported to be 0.6-24.8% compared with 0-3% in healthy mammals.

Histochemical and ultrastructural analysis of pathology and cell responses in gills of channel catfish affected with proliferative gill disease.

Pond-reared channel catfish Ictalurus punctatus with proliferative gill disease (PGD), caused by the myxozoan parasite Henneguya spp., were examined with light and transmission electron microscopy to better characterize the inflammatory response during infection. The early stages of disease are characterized by the destruction of collagen in the matrix of the gill filament cartilage causing weakness and breaks within the gill filaments.

Fish microsporidia: immune response, immunomodulation and vaccination.

Immune response to fish microsporidia is still unknown and there are current research trying to elucidate the events involved in the immune response to this parasite. There is evidence suggesting the role of innate immune response and it is clear that adaptive immunity plays an essential part for eliminating and then mounting a solid resistance against subsequent microsporidian infections. This review article discusses the main mechanisms of resistance to fish microsporidia, which are considered under four main headings.

Comparative ultrastructure of Langerhans-like cells in spleens of ray-finned fishes (Actinopterygii).

We studied the morphology and occurrence of splenic Langerhans-like (LL) cells in species representing 11 orders of ray-finned fishes, Actinopterygii. LL cells were frequent in spleen tissue of species among Cypriniformes, Esociformes, Salmoniformes, and Pleuronectiformes. These cells contained granules which resembled Birbeck granules known to occur in mammalian Langerhans cells.

Phylogeny and morphology of Glugea hertwigi from rainbow smelt Osmerus mordax found in Prince Edward Island, Canada.

Infection of rainbow smelt Osmerus mordax with the microsporidian Glugea hertwigi was diagnosed for the first time in Prince Edward Island, Canada. The prevalence of infection was 24%, 45 infected out of 187 examined fish captured in February and March 2009. Both large and small xenomas of G.

Langerin/CD207 positive dendritic-like cells in the haemopoietic tissues of salmonids.

The presence of dendritic cells in fish is studied with immunohistochemistry using a commercially available antibody developed against Langerin/CD207 present in human Langerhans cells. Langerin/CD207, a protein known to be associated with the development of Birbeck granules in human and murine systems, was found to be expressed within the cytoplasm of spleen and head kidney cells of Atlantic salmon (Salmo salar) and rainbow trout (Oncorhynchus mykiss). Reactivity was also observed within a few number of cells within the head kidney of Atlantic salmon, but not observed in any other tissues examined.

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.

Comparative cellular morphology suggesting the existence of resident dendritic cells within immune organs of salmonids.

This report is the first morphological description of cells that resemble dendritic cells, which appear to form resident populations within the spleen and anterior kidney of fish. Based on examination of three salmonid species, including, rainbow trout, brook trout, and Atlantic salmon, the cells were most abundant in the spleen, although they were always present in the anterior kidney. The cells appeared diffusely distributed, often near blood vessels of the spleen and kidney of healthy fish and within the epithelium, connective tissue, and blood vessels of rainbow trout gills with experimentally induced microsoporidial gill disease.

Pathological effects caused by chronic treatment of rainbow trout with indomethacin.

The purpose of this study was to determine adequate dose ranges and to test for side effects associated with chronic treatment of fish with indomethacin. Rainbow trout Oncorhynchus mykiss were orally treated with indomethacin at various nominal concentrations: a negative control (0 mg/kg) and low (5 mg/kg), medium (10 mg/kg), and high doses (15 mg/kg) daily for 30 d. A dose-associated mortality was observed, as cumulative mortality was 3, 13, and 33%, respectively, in the three indomethacin dose groups.

Development of an effective whole-spore vaccine to protect against microsporidial gill disease in rainbow trout (Oncorhynchus mykiss) by using a low-virulence strain of Loma 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.

Ultrastructural examination of the host cellular response in the gills of Atlantic salmon, Salmo salar, with amoebic gill disease.

Gills from Atlantic salmon with experimentally induced amoebic gill disease (Neoparamoeba spp.) were examined with transmission electron microscopy to assess pathology and host-cell responses. Amoebae were found either on the surface epithelium or with pseudopodia extending deeply into invaginations of epithelial cells.

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.

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.