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...

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...

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...

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...

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 ...

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...

Survival analysis techniques were used to compare experimental exposure methods of Loma salmonae (Microspora) in rainbow trout (RBT) by measuring xenoma onset and clearance time. Twenty-eight naive RBT were exposed per os (fed L. salmonae spores) and 28 RBT were exposed by cohabitation with 28 L. sa...

An experiment was designed to study the effect of dietary quinine hydrochloride (61 mg/kg of fish/day), on the rate of xenoma formation in the gills of Loma salmonae-infected juvenile rainbow trout maintained at a water temperature of 15 degrees C. Almost all (90.9%) control fish had developed xenom...

In the spring of 1988 more than 30% of 13 000 market weight rainbow trout died on a trout farm in southwestern Ontario. The fish showed signs typical of oxygen deprivation with listlessness, crowding of water inlets and gasping at the water surface. Water temperature, pH and oxygen levels were norma...

Two trials were conducted to assess the effects of repeated prophylactic formalin treatments on the gill structure of salmonids. In trial 1, which involved Atlantic salmon, approaching smoltification in a commercial facility, fish were treated with either 167 or 250 mg/litre formalin for 90 min ever...

Ocular lesions associated with natural and experimental outbreaks of gas bubble disease (GBD) in commercial salmonids were assessed histologically and by scanning electron microscopy. Small gas emboli were first detected in the choroid gland of the posterior uvea. In subacute and chronic cases, bubb...

The effects of twice weekly exposure to formalin [formaldehyde] (200 mg/litre in a 1-h static bath) on juvenile rainbow trout Oncorhynchus mykiss (57.4 g initial weight) were assessed in a 12-week growth trial. Growth rates, appetite, feed conversion and body condition index of fish were not signifi...

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, Oncorhynch...

Clinical signs associated with L. salmonae infection in Pacific salmon (Oncorhynchus tshawytscha (Walbaum)) arise when the parasite enters sporogony and forms xenoparasitic complexes (xenomas) within the gill. A thermal unit (TU) model, devised to predict the timing of xenoma formation, under condit...

Diseases are an integral part of the existence of all animals including both cultured and wild fish populations. Diseases among cultured fish can cause death, poor growth and food conversion, increased production costs and interrupted production schedules. The main objective of this study was to con...

In November 1991 the daily mortality rate increased from 0.01 to 0.06% in 2 netpen-reared Atlantic salmon cages at a fish farm located in coastal waters off British Columbia. Clinical signs and PM findings were consistent with those of a disease associated with a rickettsia-like organism in farmed C...