Bacteriomic Profiling of Branchial Lesions Induced by Neoparamoeba perurans Challenge Reveals Commensal Dysbiosis and an Association with Tenacibaculum dicentrarchi in AGD-Affected Atlantic Salmon (Salmo salar L.)

Amoebic gill disease is a parasitic condition that commonly affects marine farmed Atlantic salmon. The causative agent, Neoparamoeba perurans, induces a marked proliferation of the gill mucosa and focal superficial necrosis upon branchial lesions. The effect that amoebic branchialitis has upon gill associated commensal bacteria is unknown. A 16S rRNA sequencing approach was employed to profile changes in bacterial community composition, within amoebic gill disease (AGD)-affected and non-affected gill tissue. The bacterial diversity of biopsies with and without diseased tissue was significantly lower in the AGD-affected fish compared to uninfected fish. Furthermore, within the AGD-affected tissue, lesions appeared to contain a significantly higher abundance of the Flavobacterium, Tenacibaculum dicentrarchi compared to adjunct unaffected tissues. Quantitative PCR specific to both N. perurans and T. dicentrarchi was used to further examine the co-abundance of these known fish pathogens. A moderate positive correlation between these pathogens was observed. Taken together, the present study sheds new light on the complex interaction between the host, parasite and bacterial communities during AGD progression. The role that T. dicentrarchi may play in this complex relationship requires further investigation.

Download Full-text

Comparison of histologic methods for the detection of Desmozoon lepeophtherii spores in the gills of Atlantic salmon

Journal of Veterinary Diagnostic Investigation ◽

10.1177/1040638719887707 ◽

2019 ◽

Vol 32 (1) ◽

pp. 142-146

Author(s):

Ana Herrero ◽

Francesc Padrós ◽

Sara Pflaum ◽

Chris Matthews ◽

Jorge del-Pozo ◽

...

Keyword(s):

Atlantic Salmon ◽

Gill Tissue ◽

Serial Sections ◽

Calcofluor White ◽

Tissue Sections ◽

Hematoxylin And Eosin ◽

Gill Disease ◽

Farmed Atlantic Salmon ◽

Small Clusters ◽

Significant Underestimation

Desmozoon lepeophtherii is a microsporidian associated with gill disease in farmed Atlantic salmon ( Salmo salar). Detection of the parasite in histologic tissue sections is challenging using common histochemical stains given that the small, widely distributed parasite spores typically occur individually or in small clusters. We compared the ability of 4 histologic methods to detect D. lepeophtherii spores in serial sections of Atlantic salmon gill tissue: hematoxylin and eosin (H&E), Gram–Twort (GT), calcofluor white (CW), and immunohistochemistry (IHC). Using CW as a benchmark to calculate a relative ratio, IHC consistently detected more spores than CW (median: 1.3), followed by GT (median: 0.2) and H&E (median: 0.1). IHC detected significantly more spores than GT ( p < 0.05) and H&E ( p < 0.05), and GT more than H&E ( p < 0.05). We found significant underestimation of numbers of microsporidia spores in gill disease in Atlantic salmon using conventional histochemical stains and recommend the use of CW or IHC to detect the parasite in tissue sections.

Download Full-text

Searching for the sweet spot of amoebic gill disease of farmed Atlantic salmon: the potential role of glycan-lectin interactions in the adhesion of Neoparamoeba perurans

International Journal for Parasitology ◽

10.1016/j.ijpara.2020.11.009 ◽

2021 ◽

Author(s):

P.C. Lima ◽

L. Hartley-Tassell ◽

O. Cooper ◽

J.W. Wynne

Keyword(s):

Atlantic Salmon ◽

Potential Role ◽

Sweet Spot ◽

Gill Disease ◽

Farmed Atlantic Salmon

Download Full-text

Transcriptome profiling the gills of amoebic gill disease (AGD)-affected Atlantic salmon (Salmo salarL.): a role for tumor suppressor p53 in AGD pathogenesis?

Physiological Genomics ◽

10.1152/physiolgenomics.00320.2005 ◽

2006 ◽

Vol 26 (1) ◽

pp. 15-34 ◽

Cited By ~ 58

Author(s):

Richard N. Morrison ◽

Glenn A. Cooper ◽

Ben F. Koop ◽

Matthew L. Rise ◽

Andrew R. Bridle ◽

...

Keyword(s):

Tumor Suppressor ◽

Atlantic Salmon ◽

Gill Tissue ◽

Transcriptome Profiling ◽

Global Gene Expression ◽

Nuclear Antigen ◽

Independent Experiment ◽

Gill Disease ◽

P53 Tumor Suppressor Protein ◽

Microarray Analyses

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.

Download Full-text

First cases of amoebic gill disease (AGD) in Norwegian seawater farmed Atlantic salmon, Salmo salar L., and phylogeny of the causative amoeba using 18S cDNA sequences

Journal of Fish Diseases ◽

10.1111/j.1365-2761.2007.00893.x ◽

2008 ◽

Vol 31 (3) ◽

pp. 205-214 ◽

Cited By ~ 77

Author(s):

T Steinum ◽

A Kvellestad ◽

L B Rønneberg ◽

H Nilsen ◽

A Asheim ◽

...

Keyword(s):

Atlantic Salmon ◽

Salmo Salar ◽

Cdna Sequences ◽

Atlantic Salmon Salmo Salar ◽

Gill Disease ◽

Farmed Atlantic Salmon

Download Full-text

Temporal changes in infections with some pathogens associated with gill disease in farmed Atlantic salmon ( Salmo salar L)

Aquaculture ◽

10.1016/j.aquaculture.2016.10.011 ◽

2017 ◽

Vol 468 ◽

pp. 126-134 ◽

Cited By ~ 16

Author(s):

G.S Gunnarsson ◽

E Karlsbakk ◽

S Blindheim ◽

H Plarre ◽

A.K Imsland ◽

...

Keyword(s):

Atlantic Salmon ◽

Salmo Salar ◽

Temporal Changes ◽

Atlantic Salmon Salmo Salar ◽

Gill Disease ◽

Farmed Atlantic Salmon

Download Full-text

Dynamic Gill and Mucous Microbiomes Track an Amoebic Gill Disease Episode in Farmed Atlantic Salmon

10.21203/rs.3.rs-29747/v1 ◽

2020 ◽

Author(s):

Victor Blasco Birlanga ◽

Grace McCormack ◽

Umer Zeeshan Ijaz ◽

Eugene McCarthy ◽

Cindy Smith ◽

...

Keyword(s):

Atlantic Salmon ◽

Rrna Genes ◽

Prokaryotic Community ◽

Sampling Campaign ◽

Healthy State ◽

Disease Episode ◽

Gill Disease ◽

Farmed Atlantic Salmon ◽

18S Rrna Genes ◽

Pcr Targeting

Abstract Background Amongst gill disorders in Atlantic salmon, amoebic gill disease (AGD) is currently one of the most common and virulent, resulting in large losses for the aquaculture industry. However, our understanding of the role of the gill microbiome during AGD development is limited. Thus, we undertook a longitudinal study with the main objective of characterising the microbiome of gill, and mucous, samples from farmed Atlantic salmon before, and during, an AGD episode. Using a newly optimised DNA extraction protocol, we sequenced rRNA genes from 90 Atlantic salmon gill microbiomes from a fish farm (West coast of Ireland) over the course of a summer season. The first aetiological agent of AGD, Neoparamoeba perurans , was quantified using PCR targeting 18S rRNA genes. The same analyses were done using mucous samples as suitable, non-lethal alternatives to gill samples. Microbiome features across the sampling campaign were distinguished, focusing on patterns before and during the AGD episode. Results The richness and balance of the prokaryotic community on gills were trending upwards prior to the first appearance of AGD symptoms. The microbiome changed significantly, with reduced diversity and balance, after the AGD episode was confirmed, and the changing bacterial community was driven by competitive exclusion. However, this trend was reversed with the application of a first, and a second, freshwater bath treatment. Mucous samples behaved similarly. The variance of the entire prokaryotic community from both gill and mucous samples was significantly affected by the abundance of N. perurans . Rubritalea sp. were abundant in every gill and mucous sample; however, other genera ( Dyadobacter, Shewanella and Pedobacter ) were maximally abundant in gill and mucous samples 12 days prior to the first detection of AGD symptoms. Conclusions Gill and mucous microbiomes changed significantly after the first AGD symptoms were evident, correlating with N. perurans concentrations and supporting a connection between the development of the AGD and the gill microbiome. Those changes, however, were reversed by the application of multiple freshwater treatments, which returned gills to a more healthy state. Despite differences between microbiome features from gill and mucous samples, the data establish mucous scrapings as suitable, non-lethal substitutes for partial characterisation of the whole prokaryotic community from fish gills. The genus Shewanella was widely present, and significantly more abundant, immediately before the first AGD symptoms than during the AGD episode, marking this out as a feasible, putative target in identifying proxies for early detection of AGD.

Download Full-text

Host-Parasite Interaction of Atlantic salmon (Salmo salar) and the Ectoparasite Neoparamoeba perurans in Amoebic Gill Disease

Frontiers in Immunology ◽

10.3389/fimmu.2021.672700 ◽

2021 ◽

Vol 12 ◽

Author(s):

Natasha A. Botwright ◽

Amin R. Mohamed ◽

Joel Slinger ◽

Paula C. Lima ◽

James W. Wynne

Keyword(s):

Gene Expression ◽

Atlantic Salmon ◽

Differential Gene Expression ◽

Salmo Salar ◽

Production Cycle ◽

Data Set ◽

Transcriptomic Response ◽

Differential Gene ◽

Gill Disease ◽

Host Parasite

Marine farmed Atlantic salmon (Salmo salar) are susceptible to recurrent amoebic gill disease (AGD) caused by the ectoparasite Neoparamoeba perurans over the growout production cycle. The parasite elicits a highly localized response within the gill epithelium resulting in multifocal mucoid patches at the site of parasite attachment. This host-parasite response drives a complex immune reaction, which remains poorly understood. To generate a model for host-parasite interaction during pathogenesis of AGD in Atlantic salmon the local (gill) and systemic transcriptomic response in the host, and the parasite during AGD pathogenesis was explored. A dual RNA-seq approach together with differential gene expression and system-wide statistical analyses of gene and transcription factor networks was employed. A multi-tissue transcriptomic data set was generated from the gill (including both lesioned and non-lesioned tissue), head kidney and spleen tissues naïve and AGD-affected Atlantic salmon sourced from an in vivo AGD challenge trial. Differential gene expression of the salmon host indicates local and systemic upregulation of defense and immune responses. Two transcription factors, znfOZF-like and znf70-like, and their associated gene networks significantly altered with disease state. The majority of genes in these networks are candidates for mediators of the immune response, cellular proliferation and invasion. These include Aurora kinase B-like, rho guanine nucleotide exchange factor 25-like and protein NDNF-like inhibited. Analysis of the N. perurans transcriptome during AGD pathology compared to in vitro cultured N. perurans trophozoites, as a proxy for wild type trophozoites, identified multiple gene candidates for virulence and indicates a potential master regulatory gene system analogous to the two-component PhoP/Q system. Candidate genes identified are associated with invasion of host tissue, evasion of host defense mechanisms and formation of the mucoid lesion. We generated a novel model for host-parasite interaction during AGD pathogenesis through integration of host and parasite functional profiles. Collectively, this dual transcriptomic study provides novel molecular insights into the pathology of AGD and provides alternative theories for future research in a step towards improved management of AGD.

Download Full-text