In determining the effective vaccine spore dose of a low-virulence strain of Loma salmonae to limit micro-sporidial 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 t...

Resistance to re-infection of rainbow trout to Loma salmonae, a microsporidian gill parasite has been previously documented and this study examined how rapidly this resistance develops. Naive rainbow trout were inoculated intraperitoneally (IP) with an inactivated spore-based vaccine and were then g...

The early ultrastructural stages of Loma salmonae were studied in the gills of experimentally infected rainbow trout. No parasitic stages were identified during the first 2 wk of the infection. By week 3 postexposure (PE), uninucleate and binucleate meronts were recognized within host cells (no xeno...

Epidemic mortalities of chinook salmon alevins (Oncorhynchus tshawytscha) have occurred annually at a freshwater hatchery at the Chehalis River, British Columbia, Canada, since 1982. Previous work has identified branchial epithelial hyperplasia as the predominant pathological change. Our initial wor...

Two studies were designed to quantify the effect of water temperature and flow rate on the transmission potential of the important salmonid gill pathogen, Loma salmonae. Using survival analysis, increased water temperature and low flow rates were determined as risk factors for the transmission of mi...

Infection by a microsporidian of the genus Loma was found in gills of cod Gadus morhua. Xenomas contained parasites in multiple stages of development. Some spores looked empty and had everted polar tubes, which were either straight or coiled. These polar tubes were scattered throughout the xenoma cy...

We used hydrogen peroxide to reproduce gill lesions typical of a broad assemblage of gill diseases encountered in aquaculture, and examined the degree of growth rate depression that it caused. Additionally, we compared growth rates of 60 gill-damaged fish when they were either kept separate from (n=...

Loma salmonae, a microsporidian parasite of salmonids of the genus Oncorhynchus, is a significant cause of economic loss in pen-reared chinook salmon (O. tschawytscha). Final stages of L. salmonae infections are easily recognized by the xenomas that form in the gills during sporogony. However, early...

The sequence of host changes following the rupture of spore-laden xenomas of the microsporidian Loma salmonae during Microsporidial Gill Disease of Salmon was deduced from ultrastructural examination of the gills of naturally infected, moribund, chinook salmon from a commercial aquaculture site. The...

This study evaluated the regulatory effects of water temperature on the development of branchial xenomas caused by Loma salmonae using a high-dose per os-challenge model compared with a low-dose cohabitation-challenge model. Approximately 275 juvenile rainbow trout (RBT), Oncorhynchus mykiss, were r...

Growth indices were examined in 24 identically managed tanks, each containing 120 diploid juvenile rainbow trout (initial mean body weight, 9.3 g) during a 12-week study to examine tank effects associated with tank location in a multi user research facility. Growth indices included mean body weight,...

Experimental infection of rainbow trout juveniles with L. salmonae at a water temperature of 15 degrees C yielded detectable parasite DNA within the gills by the second week after exposure (AE) and detectable spore-wall antigen within developing xenomas by week 3 AE, as determined by in situ hybridi...

The principal lesions due to the ciliate Anophryoides haemophila in experimentally infected lobsters are observed in the gills and connective tissue from the 9th week post-infection. These lesions were not related to the inoculum of parasites and were consistent in all inoculum studies (2000, 10 000...

Experiments involving 200 rainbow trout showed that host defence mechanisms in sea lice-infested fish are impaired, predisposing fish to subsequent infections to a second pathogen, such as the microsporidian parasite Loma salmonae. Macrophage impairment in lice-infested fish occurred when sea lice b...

Chloramine-T is a commonly used therapeutic agent for the treatment of bacterial gill disease and related phenomena in the salmonid aquaculture industry. There is little known about its effects on healthy fish. Using a 24-tank replicate growth assay system, rainbow trout (Oncorhynchus mykiss) (avera...

Juvenile brook trout (Salvelinus fontinalis), rainbow trout (Oncorhynchus mykiss), Atlantic salmon (Salmo salar) and Arctic charr (Salvelinus alpinus) were experimentally infected with a Loma salmonae variant to assess its infectivity within a range of salmonid species. The study shows that after in...

The purpose of this research was to investigate the salinity and formalin sensitivity of a ciliate parasite (Anophryoides haemophila) of the American lobster (Homarus americanus), and to examine the target-animal (lobster) safety of chemical-bath treatments involving low salinity, formalin, or chlor...

Healthy gills from fingerling rainbow trout were dissected and fixed using either a conventional 0.1M cacodylate buffered 2.5% glutaraldehyde or the same fixative with 2% (w/v) Alcian blue added. The tissues were processed for light and electron microscopy. Skin tissue samples from cases of necrotic...

This study was designed to investigate the effect of single short-duration bath-treatment with hydrogen peroxide (1000, 1250 or 1500 mg/l for 20 min), as currently used in treatment for sea lice, on the growth rate and gill morphology of rainbow trout. All three dose levels significantly reduced the...

Loma salmonae, an obligate intracellular microsporidian parasite, is the causal agent of microsporidial gill disease of salmon (MGDS), characterized by the production, growth and eventual rupture of spore-filled xenomas. MGDS in farmed chinook salmon remains occult until xenoma rupture, at which tim...

Two trials were designed to quantify the effect of feeding ratio and fish size on the cohabitation transmission of Loma salmonae, the causative agent of microsporidial gill disease (MGD) in salmonids, Oncorhynchus spp. To evaluate the effect of feeding ratio on disease onset, groups of 45 rainbow tr...

The main objective of this investigation was to examine the ultrastructural features of gills from rainbow trout experimentally infected with Loma salmonae to determine the morphological events that occur during the late stages of development of this parasite. Peripheral distribution of the mature p...