Experimental exposure to low concentrations of Neoparamoeba perurans induces amoebic gill disease in Atlantic salmon

Neoparamoeba spp. are amphizoic amoebae with the capacity to colonize the gills of some marine fish, causing AGD. Here, the gill tissue transcriptome response of Atlantic salmon ( Salmo salar L.) to AGD is described. Tanks housing Atlantic salmon were inoculated with Neoparamoeba spp. and fish sampled at time points up to 8 days postinoculation (pi.). Gill tissues were taken from AGD-affected fish, and a DNA microarray was used to compare global gene expression against tissues from AGD-unaffected fish. A total of 206 genes, representing 190 unique transcripts, were reproducibly identified as up- or downregulated in response to Neoparamoeba spp. infection. Informative transcripts having GO biological process identifiers were grouped according to function. Although a number of genes were placed into each category, no distinct patterns were observed. One Atlantic salmon cDNA that was upregulated in infected gill relative to noninfected gill at 114 and 189 h pi. showed significant identity with the Xenopus, mouse, and human anterior gradient-2 (AG-2) homologs. Two Atlantic salmon AG-2 mRNA transcripts, designated asAG-2/1 and asAG-2/2, were cloned, sequenced, and shown to be predominantly expressed in the gill, intestine, and brain of a healthy fish. In AGD-affected fish, differential asAG-2 expression was confirmed in samples used for microarray analyses as well as in AGD-affected gill tissue taken from fish in an independent experiment. The asAG-2 upregulation was restricted to AGD lesions relative to unaffected tissue from the same gill arch, while p53 tumor suppressor protein mRNA was concurrently downregulated in AGD lesions. Differential expression of p53-regulated transcripts, proliferating cell nuclear antigen and growth arrest and DNA damage-inducible gene-45β (GADD45β) in AGD lesions, suggests a role for p53 in AGD pathogenesis. Thus AGD may represent a novel model for comparative analysis of p53 and p53-regulated pathways.

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The diversity and pathogenicity of amoebae on the gills of Atlantic salmon (Salmo salar) with amoebic gill disease (AGD)

10.14264/uql.2020.1014 ◽

2020 ◽

Author(s):

Chloe English

Keyword(s):

Atlantic Salmon ◽

Salmo Salar ◽

Atlantic Salmon Salmo Salar ◽

Gill Disease

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Immersion challenge of naïve Atlantic salmon with cultured Nolandella sp. and Pseudoparamoeba sp. did not increase the severity of Neoparamoeba perurans ‐induced amoebic gill disease (AGD)

Journal of Fish Diseases ◽

10.1111/jfd.13319 ◽

2020 ◽

Author(s):

Chloe J. English ◽

Natasha A. Botwright ◽

Mark B. Adams ◽

Andrew C. Barnes ◽

James W. Wynne ◽

...

Keyword(s):

Atlantic Salmon ◽

Gill Disease

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Cyclic Hypoxia Exposure Accelerates the Progression of Amoebic Gill Disease

Pathogens ◽

10.3390/pathogens9080597 ◽

2020 ◽

Vol 9 (8) ◽

pp. 597

Author(s):

Tina Oldham ◽

Tim Dempster ◽

Philip Crosbie ◽

Mark Adams ◽

Barbara Nowak

Keyword(s):

Atlantic Salmon ◽

Economic Losses ◽

Post Inoculation ◽

Diel Pattern ◽

Marine Aquaculture ◽

Hypoxia Exposure ◽

Qpcr Analysis ◽

Serious Infections ◽

Gill Disease ◽

Hypoxic Treatment

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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Electrical Responses of the Olfactory Epithelium of Atlantic Salmon (Salmo salar)

Journal of the Fisheries Research Board of Canada ◽

10.1139/f71-080 ◽

1971 ◽

Vol 28 (4) ◽

pp. 565-572 ◽

Cited By ~ 122

Author(s):

A. M. Sutterlin ◽

N. Sutterlin

Keyword(s):

Amino Acids ◽

Atlantic Salmon ◽

Salmo Salar ◽

Olfactory Epithelium ◽

Spike Activity ◽

Olfactory Mucosa ◽

Oscillatory Activity ◽

Atlantic Salmon Salmo Salar ◽

Low Concentrations ◽

Complex Solutions

Multiunit spike activity was recorded from the olfactory mucosa of Atlantic salmon (Salmo salar) using metal-filled glass microelectrodes. A number of simple and complex solutions were tested for stimulatory effectiveness. Amino acids as a class of compounds were highly stimulatory; little or no response was obtained to a variety of simple sugars, n-aliphatic acids, alcohols, or amino-substituted alcohols. An increase in asynchronous spike activity was evoked by low concentrations of amino acids and oscillatory activity was evoked by higher concentrations of amino acids. Brief treatment of the epithelium with dilute solutions of HgCl2 blocked the chemosensitivity of the receptors.

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