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Cyclic Hypoxia Exposure Accelerates the Progression of Amoebic Gill Disease

Amoebic gill disease (AGD), caused by the amoeba Neoparamoeba perurans, has led to considerable economic losses in every major Atlantic salmon producing country, and is increasing in frequency. The most serious infections occur during summer and autumn, when temperatures are high and poor dissolved...

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Autores principales: Oldham, Tina, Dempster, Tim, Crosbie, Philip, Adams, Mark, Nowak, Barbara
Formato: Online Artículo Texto
Lenguaje:English
Publicado: MDPI 2020
Materias:
Acceso en línea:https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7460382/
https://www.ncbi.nlm.nih.gov/pubmed/32707755
http://dx.doi.org/10.3390/pathogens9080597
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author Oldham, Tina
Dempster, Tim
Crosbie, Philip
Adams, Mark
Nowak, Barbara
author_facet Oldham, Tina
Dempster, Tim
Crosbie, Philip
Adams, Mark
Nowak, Barbara
author_sort Oldham, Tina
collection PubMed
description Amoebic gill disease (AGD), caused by the amoeba Neoparamoeba perurans, has led to considerable economic losses in every major Atlantic salmon producing country, and is increasing in frequency. The most serious infections occur during summer and autumn, when temperatures are high and poor dissolved oxygen (DO) conditions are most common. Here, we tested if exposure to cyclic hypoxia at DO saturations of 40–60% altered the course of infection with N. perurans compared to normoxic controls maintained at ≥90% DO saturation. Although hypoxia exposure did not increase initial susceptibility to N. perurans, it accelerated progression of the disease. By 7 days post-inoculation, amoeba counts estimated from qPCR analysis were 1.7 times higher in the hypoxic treatment than in normoxic controls, and cumulative mortalities were twice as high (16 ± 4% and 8 ± 2%), respectively. At 10 days post-inoculation, however, there were no differences between amoeba counts in the hypoxic and normoxic treatments, nor in the percentage of filaments with AGD lesions (control = 74 ± 2.8%, hypoxic = 69 ± 3.3%), or number of lamellae per lesion (control = 30 ± 0.9%, hypoxic = 27.9 ± 0.9%) as determined by histological examination. Cumulative mortalities at the termination of the experiment were similarly high in both treatments (hypoxic = 60 ± 2%, normoxic = 53 ± 11%). These results reveal that exposure to cyclic hypoxia in a diel pattern, equivalent to what salmon are exposed to in marine aquaculture cages, accelerated the progression of AGD in post-smolts.
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spelling pubmed-74603822020-09-02 Cyclic Hypoxia Exposure Accelerates the Progression of Amoebic Gill Disease Oldham, Tina Dempster, Tim Crosbie, Philip Adams, Mark Nowak, Barbara Pathogens Article Amoebic gill disease (AGD), caused by the amoeba Neoparamoeba perurans, has led to considerable economic losses in every major Atlantic salmon producing country, and is increasing in frequency. The most serious infections occur during summer and autumn, when temperatures are high and poor dissolved oxygen (DO) conditions are most common. Here, we tested if exposure to cyclic hypoxia at DO saturations of 40–60% altered the course of infection with N. perurans compared to normoxic controls maintained at ≥90% DO saturation. Although hypoxia exposure did not increase initial susceptibility to N. perurans, it accelerated progression of the disease. By 7 days post-inoculation, amoeba counts estimated from qPCR analysis were 1.7 times higher in the hypoxic treatment than in normoxic controls, and cumulative mortalities were twice as high (16 ± 4% and 8 ± 2%), respectively. At 10 days post-inoculation, however, there were no differences between amoeba counts in the hypoxic and normoxic treatments, nor in the percentage of filaments with AGD lesions (control = 74 ± 2.8%, hypoxic = 69 ± 3.3%), or number of lamellae per lesion (control = 30 ± 0.9%, hypoxic = 27.9 ± 0.9%) as determined by histological examination. Cumulative mortalities at the termination of the experiment were similarly high in both treatments (hypoxic = 60 ± 2%, normoxic = 53 ± 11%). These results reveal that exposure to cyclic hypoxia in a diel pattern, equivalent to what salmon are exposed to in marine aquaculture cages, accelerated the progression of AGD in post-smolts. MDPI 2020-07-22 /pmc/articles/PMC7460382/ /pubmed/32707755 http://dx.doi.org/10.3390/pathogens9080597 Text en © 2020 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (http://creativecommons.org/licenses/by/4.0/).
spellingShingle Article
Oldham, Tina
Dempster, Tim
Crosbie, Philip
Adams, Mark
Nowak, Barbara
Cyclic Hypoxia Exposure Accelerates the Progression of Amoebic Gill Disease
title Cyclic Hypoxia Exposure Accelerates the Progression of Amoebic Gill Disease
title_full Cyclic Hypoxia Exposure Accelerates the Progression of Amoebic Gill Disease
title_fullStr Cyclic Hypoxia Exposure Accelerates the Progression of Amoebic Gill Disease
title_full_unstemmed Cyclic Hypoxia Exposure Accelerates the Progression of Amoebic Gill Disease
title_short Cyclic Hypoxia Exposure Accelerates the Progression of Amoebic Gill Disease
title_sort cyclic hypoxia exposure accelerates the progression of amoebic gill disease
topic Article
url https://www.ncbi.nlm.nih.gov/pmc/articles/PMC7460382/
https://www.ncbi.nlm.nih.gov/pubmed/32707755
http://dx.doi.org/10.3390/pathogens9080597
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