The effects of the following six treatments against Loma salmonae, a microsporidian gill pathogen, were examined in rainbow trout: fumagillin (high dose), pyrimethamine + sulphaquinoxaline, albendazole, amprolium, fumagillin (low dose), and metronidazole. The fish were infected by mouth and the trea...

The induction of protection against xenoma development by vaccinated (previously exposed to a low-virulence strain of Loma salmonae; n=40) and naive (n=40) rainbow trout (Oncorhynchus mykiss) challenged with the virulent typical strain of L. salmonae, was determined. Prevalence of infection was lowe...

Few microsporidia have been reported from whitefish species (subfamily Coregoninae). For the most part, these microsporidia have been incompletely described. In a survey of parasites of mountain whitefish Prosopium williamsoni collected from Kootenay Lake, British Columbia, we encountered an unusual...

The neural pathology associated with spontaneous cases of bacterial kidney disease (BKD), in five species of commercially reared salmonids, was investigated histopathologically and with immunofluorescence. Patterns of localisation of the causative organism of BKD within the central nervous system su...

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...

Piscirickettsia salmonis, the etiologic agent of salmonid rickettsial septicemia (SRS), or piscirickettsiosis, causes substantial economic losses to the salmon industry. The pathogenesis of the disease has not been fully characterized. The aim of this study is to describe the hepatic lesions associa...

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 groups of healthy chinook salmon (Oncorhynchus tshawytscha) were experimentally exposed to gas supersaturated groundwater. Gross lesions consistent with gas bubble disease (GBD) developed. Vascular lesions associated with intravascular gas bubbles were examined with light and scanning electron m...

Twice-weekly treatment of juvenile rainbow trout with hydrogen peroxide at 200 mg/litre for 1 h was effective in limiting the degree of fin and epithelial damage associated with an experimental thermally promoted outbreak of columnaris disease attributable to Flexibacter columnaris [Cytophaga column...

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=...

We reviewed the clinical presentations and histopathology of 118 diagnostic submissions of trout with infectious gill diseases from commercial trout farms within Ontario. Bacterial gill disease (BGD) (56%) and nodular gill disease (NGD) (26.2%) together accounted for 82.2% of these submissions. Subm...

Project Loma is a multidisciplinary collaborative research programme aimed to develop the treatment and control of the microsporidian parasite Loma salmonae which is the cause of Microsporidial Gill Disease of Salmon (MGDS). Recent studies have shown that the principal host target, salmonids within ...

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...

Outbreaks of columnaris diseases occurred on 2 trout farms in July 1988. Only a small percentage of fish was affected on each farm. On one farm affected fish had areas of destruction of the ventral body wall leading to herniation of internal organs. On the second farm lesions resembled those of furu...

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...

Loma salmonae is an intracellular obligate parasite of farmed chinook salmon (Oncorhynchus tshawtscha) and is the causative agent for microsporidial gill disease (MGD). The infection occurs mainly in secondary gill lamellae, with the formation of large white spore-laden xenomas within the endothelia...