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Evaluation of fixation methods for demonstration of Neoparamoeba perurans infection in Atlantic salmon, Salmo salar L., gills


Cadoret, K and Bridle, AR and Leef, MJ and Nowak, BF, Evaluation of fixation methods for demonstration of Neoparamoeba perurans infection in Atlantic salmon, Salmo salar L., gills, Journal of Fish Diseases, 36, (10) pp. 831-839. ISSN 0140-7775 (2013) [Refereed Article]

Copyright Statement

Copyright 2013 Blackwell Publishing Ltd

DOI: doi:10.1111/jfd.12078


Formaldehyde-based fixatives are generally employed in histopathology despite some significant disadvantages associated with their usage. Formaldehyde fixes tissue by covalently cross-linking proteins, a process known to mask epitopes which in turn can reduce the intensity of immunohistochemical stains widely used in disease diagnostics. Additionally, formaldehyde fixation greatly limits the ability to recover DNA and mRNA from fixed specimens to the detriment of further downstream molecular analyses. Amoebic gill disease (AGD) has been reliably diagnosed from histological examination of gills although complementary methods such as in situ hybridization (ISH) and polymerase chain reaction (PCR) are required to confirm the presence of Neoparamoeba perurans, the causative agent of AGD. As molecular techniques are becoming more prevalent for pathogen identification, there is a need to adapt specimen collection and preservation so that both histology and molecular biology can be used to diagnose the same sample. This study used a general approach to evaluate five different fixatives for Atlantic salmon, Salmo salar L., gills. Neutral-buffered formalin and seawater Davidson's, formaldehyde-based fixatives commonly used in fish histopathology, were compared to formalin-free commercial fixatives PAXgene®, HistoChoice™MB* and RNAlater™. Each fixative was assessed by a suite of analyses used to demonstrate AGD including routine histochemical stains, immunohistochemical stains, ISH and DNA extraction followed by PCR. All five fixatives were suitable for histological examination of Atlantic salmon gills, with seawater Davidson's providing the best quality histopathology results. Of the fixatives evaluated seawater Davidson's and PAXgene® were shown to be the most compatible with molecular biology techniques. They both provided good DNA recovery, quantity and integrity, from fixed and embedded specimens. The capacity to preserve tissue and cellular morphology in addition to allowing molecular analyses of the same specimens makes seawater Davidson's and PAXgene® appear to be the best fixation methods for diagnosis and research on AGD in Atlantic salmon gills.

Item Details

Item Type:Refereed Article
Keywords:amoebic gill disease, diagnostic, fixative evaluation, histopathology, molecular pathology
Research Division:Agricultural, Veterinary and Food Sciences
Research Group:Fisheries sciences
Research Field:Aquaculture
Objective Division:Animal Production and Animal Primary Products
Objective Group:Fisheries - aquaculture
Objective Field:Fisheries - aquaculture not elsewhere classified
UTAS Author:Cadoret, K (Ms Karine Cadoret)
UTAS Author:Bridle, AR (Associate Professor Andrew Bridle)
UTAS Author:Leef, MJ (Dr Melanie Leef)
UTAS Author:Nowak, BF (Professor Barbara Nowak)
ID Code:84286
Year Published:2013
Web of Science® Times Cited:7
Deposited By:NC Marine Conservation and Resource Sustainability
Deposited On:2013-05-02
Last Modified:2017-11-03

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