Geology topics

J.M. Ramsay

Publications and source records attributed to J.M. Ramsay.

3 recordsLinked to original sources

USGS2009

Husbandry stress exacerbates mycobacterial infections in adult zebrafish, Danio rerio (Hamilton)

Mycobacteria are significant pathogens of laboratory zebrafish, Danio rerio (Hamilton). Stress is often implicated in clinical disease and morbidity associated with mycobacterial infections but has yet to be examined with zebrafish. The aim of this study was to examine the effects of husbandry stressors on zebrafish infected with mycobacteria. Adult zebrafish were exposed to Mycobacterium marinum or Mycobacterium chelonae, two species that have been associated with disease in zebrafish. Infected fish and controls were then subjected to chronic crowding and handling stressors and examined over an 8-week period. Whole-body cortisol was significantly elevated in stressed fish compared to non-stressed fish. Fish infected with M. marinum ATCC 927 and subjected to husbandry stressors had 14% cumulative mortality while no mortality occurred among infected fish not subjected to husbandry stressors. Stressed fish, infected with M. chelonae H1E2 from zebrafish, were 15-fold more likely to be infected than non-stressed fish at week 8 post-injection. Sub-acute, diffuse infections were more common among stressed fish infected with M. marinum or M. chelonae than non-stressed fish. This is the first study to demonstrate an effect of stress and elevated cortisol on the morbidity, prevalence, clinical disease and histological presentation associated with mycobacterial infections in zebrafish. Minimizing husbandry stress may be effective at reducing the severity of outbreaks of clinical mycobacteriosis in zebrafish facilities. ?? 2009 Blackwell Publishing Ltd.

Journal of Fish Diseases↗

USGS2009

Whole-body cortisol response of zebrafish to acute net handling stress

Zebrafish, Danio rerio, are frequently handled during husbandry and experimental procedures in the laboratory, yet little is known about the physiological responses to such stressors. We measured the whole-body cortisol levels of adult zebrafish subjected to net stress and air exposure at intervals over a 24 h period; cortisol recovered to near control levels by about 1 h post-net-stress (PNS). We then measured cortisol at frequent intervals over a 1 h period. Cortisol levels were more than 2-fold higher in net stressed fish at 3 min PNS and continued to increase peaking at 15 min PNS, when cortisol levels were 6-fold greater than the control cortisol. Mean cortisol declined from 15 to 60 min PNS, and at 60 min, net-stressed cortisol was similar to control cortisol. Because the age of fish differed between studies, we examined resting cortisol levels of fish of different ages (3, 7, 13, and 19 months). The resting cortisol values among tanks with the same age fish differed significantly but there was no clear effect of age. Our study is the first to report the response and recovery of cortisol after net handling for laboratory-reared zebrafish. ?? 2009 Elsevier B.V.

Aquaculture↗

USGS2009

Pseudoloma neurophilia infections in zebrafish Danio rerio: effects of stress on survival, growth, and reproduction.

Pseudoloma neurophilia (Microsporidia) is a common disease of zebrafish Danio rerio, including those used as research models. We conducted a study comprised of 4 separate experiments to determine the effects of husbandry stress on preexisting and experimental P. neurophilia infections and the subsequent effects on survival, infection onset and intensity, fish growth, and reproduction. In fish (AB strain) with preexisting infections, stress or feeding cortisol significantly increased mortality over 7 wk compared to no stress or cortisol treatment. In contrast, no mortality was observed in fish (TL strain) experimentally exposed to P. neurophilia over 10 wk. A third experiment involved experimental exposure of AB fish to P. neurophilia and exposure to crowding and handling stressors. No mortality was associated with P. neurophilia regardless of stress treatment over a period of 20 wk. However, the onset of infection occurred sooner in stress-treated fish. Stress significantly increased the mean intensity of infection (described as xenoma area/spinal cord area in histological sections) at Week 20 post-exposure (PE). In fish with preexisting infections, myositis was significantly greater in stressed and cortisol-treated fish than those not stressed. With experimental exposure of AB fish, stressed and infected groups weighed significantly less than the control group at Week 20 PE. Regarding fecundity, the number of larvae hatched at 5 d post fertilization was negatively associated with mean infection intensity among P. neurophilia-infected and stressed AB fish. These experiments are the first to show empirically that P. neurophilia can be associated with reduced weight and fecundity, and that stress can exacerbate the severity of the infection.

Diseases of Aquatic Organisms↗