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  • Articles  (3)
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  • Articles  (3)
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  • 1
    Electronic Resource
    Electronic Resource
    Evaluating protection against Loma salmonae generated from primary exposure of rainbow trout, Oncorhynchus mykiss (Walbaum), outside of the xenoma-expression temperature boundaries (1999)
    Oxford, UK : Blackwell Science Ltd
    Journal of fish diseases 22 (1999), S. 0 
    Details
    ISSN: 1365-2761
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: A series of challenge and re-challenge studies was conducted in which juvenile rainbow trout were exposed to the pathogen Loma salmonae, a microsporidian which typically causes xenoma formation during sporogony and inflammation in the gills as the xenomas undergo dissolution. The specific goal was to determine if a primary exposure, conducted at a water temperature outside of the range which permits the parasite to undergo sporogony and form branchial xenomas, would stimulate a protective response in the fish to a later challenge conducted under temperature conditions optimal for the parasite. Primary challenge of fish to L. salmonae at 7 °C or 21 °C blocked or limited xenoma formation, as discussed in a previous study. However, these fish had a relative percentage protection (RPP) against a second optimized exposure which matched, or was not significantly less than, the degree of protection (100%) that developed in other groups of fish that received a primary exposure throughout the range of water temperatures which permits xenoma formation. When the primary exposure was conducted at 5 °C, the RPP against the second exposure was adversely affected and declined to 61%. These findings have application to the control of L. salmonae within aquaculture, in that it may be possible to expose hatchery stocks of susceptible salmonid species to spores of L. salmonae when hatchery water temperature is at 7 °C. At this temperature, the risks of disease stemming from this primary exposure appear minimal, since xenomas fail to form. However, the degree of protection appears promising, and may be sufficient to protect fish from spore exposure occurring at netpen marine sites where the parasite may be endemic.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2761.1999.00194.x
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  • 2
    Electronic Resource
    Electronic Resource
    Effect of water temperature manipulation on a thermal unit predictive model for Loma salmonae (1999)
    Oxford, UK : Blackwell Science, Ltd
    Journal of fish diseases 22 (1999), S. 0 
    Details
    ISSN: 1365-2761
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Loma salmonae is an important microsporidian pathogen affecting the mariculture of Pacific salmon, Oncorhynchus tshawytscha (Walbaum). Clinical signs associated with infection arise when the parasite enters sporogony and forms xenoparasitic complexes (xenomas) within the gill. The present study tested a thermal unit (TU) model, which was devised to predict the timing of xenoma formation, under conditions in which water temperature changed during the course of infection. In vivo trials with juvenile trout showed that the model [TU for xenoma onset = (days post exposure) × ( °C above 7 °C)] accurately predicted the onset time for xenomas when fish were moved from either 11 or 5 °C to 15 °C at various intervals after exposure. These findings suggest that the TU model may allow aquaculturists to predict disease onset. However, the model failed when fish were moved from 15 to 5 °C at intervals after exposure. This finding suggests that the temperature-constrained phase of the life-cycle of L. salmonae occurs early on after the spore is ingested by the fish.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2761.1999.00180.x
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  • 3
    Electronic Resource
    Electronic Resource
    Loma salmonae-associated growth rate suppression in rainbow trout, Oncorhynchus mykiss (Walbaum), occurs during early onset xenoma dissolution as determined by in situ hybridization and immunohistochemistry (1998)
    Oxford, UK : Blackwell Science Ltd
    Journal of fish diseases 21 (1998), S. 0 
    Details
    ISSN: 1365-2761
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology , Medicine
    Notes: Experimental infection of rainbow trout, Oncorhynchus mykiss (Walbaum), juveniles with Loma salmonae at a water temperature of 15 °C yielded detectable parasite DNA within the gills by week 2 post-exposure (PE) and detectable spore-wall antigen within developing xenomas by week 3 PE, as determined by in situ hybridization and monoclonal antibody (Mab) based immunohistochemistry, respectively. The microsporidian was most commonly located within endothelial cells of lamellar basal channels. Whereas the onset of xenoma formation appeared to be relatively synchronous, as expected from previous studies, xenoma dissolution followed an unexpected biphasic pattern with peaks at weeks 4 and 9 PE. The onset of significant growth rate suppression, at week 4 PE in exposed fish, was temporally associated with the appearance of gill lesions which, in turn, were centred about sites of premature xenoma dissolution. The latter was determined by the detection of spore-wall antigen within lesions. Co-habitant control fish began developing xenomas by week 10, indicating the infective potential of those spores released from the principal fish during early xenoma dissolution. Although infection with L. salmonae significantly affects fish growth rates, the time-course of this suppression is limited, and as an unexpected finding, growth rate recovery commences prior to the infection’s resolution.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1046/j.1365-2761.1998.00112.x
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