Abstract
AEI Aquaculture Environment Interactions Contact the journal Facebook Twitter RSS Mailing List Subscribe to our mailing list via Mailchimp HomeLatest VolumeAbout the JournalEditorsTheme Sections AEI 7:239-251 (2015) - DOI: https://doi.org/10.3354/aei00150 A longitudinal study of amoebic gill disease on a marine Atlantic salmon farm utilising a real-time PCR assay for the detection of Neoparamoeba perurans J. K. Downes1,2,*, K. Henshilwood1, E. M. Collins1, A. Ryan3, I. O’Connor2, H. D. Rodger4, E. MacCarthy2, N. M. Ruane1 1Fish Health Unit, Marine Institute, Rinville, Oranmore, Co. Galway, Ireland 2Marine & Freshwater Research Centre, Galway Mayo Institute of Technology, Dublin Road, Galway, Ireland 3Marine Harvest Ireland, Castletownbere, Co. Cork, Ireland 4Vet Aqua International, Unit 7b, Oranmore Business Park, Oranmore, Co. Galway, Ireland *Corresponding author: jamie.downes@marine.ie ABSTRACT: Amoebic gill disease (AGD) is a proliferative gill disease of marine cultured Atlantic salmon Salmo salar, with the free-living protozoan Neoparamoeba perurans being the primary aetiological agent. The increased incidence of AGD in recent years presents a significant challenge to the Atlantic salmon farming industry in Europe. In this study, a real-time TaqMan® PCR assay was developed and validated to detect Neoparamoeba perurans on Atlantic salmon gills and further used to monitor disease progression on a marine Atlantic salmon farm in Ireland in conjunction with gross gill pathology and histopathology. The assay proved specific for N. perurans, with no cross-reactivity with the related species N. pemaquidensis, N. branchiphila or N. aestuarina, and was capable of detecting 2.68 copies of N. perurans DNA µl-1. Although the parasite was detected throughout the 18 mo period of this study, mortality peaks associated with clinical AGD were only recorded during the first 12 mo of the marine phase of the production cycle. The initial AGD outbreak resulted in peak mortality in Week 17, which was preceded by PCR detections from Week 13 onwards. Freshwater treatments were an effective method for controlling the disease, resulting in a reduction in the weekly mortality levels and also a reduction in the number of PCR-positive fish. In comparison to traditional diagnostic methods, our PCR assay proved to be highly sensitive and a valuable tool to monitor disease progression and, therefore, has the potential to provide information on the timing and effectiveness of treatments. KEY WORDS: Amoebic gill disease · Neoparamoeba perurans · Diagnostics · Atlantic salmon Full text in pdf format PreviousNextCite this article as: Downes JK, Henshilwood K, Collins EM, Ryan A and others (2015) A longitudinal study of amoebic gill disease on a marine Atlantic salmon farm utilising a real-time PCR assay for the detection of Neoparamoeba perurans. Aquacult Environ Interact 7:239-251. https://doi.org/10.3354/aei00150 Export citation RSS - Facebook - Tweet - linkedIn Cited by Published in AEI Vol. 7, No. 3. Online publication date: November 18, 2015 Print ISSN: 1869-215X; Online ISSN: 1869-7534 Copyright © 2015 Inter-Research.
Highlights
The aim of this study was to develop an alternative TaqMan® assay for the detection of N. perurans according to MIQE guidelines (Bustin et al 2009) and investigate its application in monitoring the disease through a longitudinal study on a marine Atlantic salmon site during a single production cycle
Neoparamoeba perurans was isolated from AGDaffected farmed Atlantic salmon in the west of Ireland using a method adapted from Morrison et al (2004)
Neoparamoeba perurans was successfully isolated and cultured at 18°C on malt yeast agar (MYA) plates, with washing occurring every 3 d and amoebae seeded onto fresh plates every 2 wk
Summary
In Ireland, AGD was first recorded in 1995 in a number of marine Atlantic salmon sites (Rodger & McArdle 1996, Palmer et al 1997) and continued to occur sporadically in a small number of sites since the first outbreaks (Bermingham & Mulcahy 2007). An 86% reduction in the number of amoeba remaining in the gills has been observed following freshwater baths (Clark et al 2003). This method of treatment can add extra costs and is labourintensive, and several treatments may be required over the course of a production cycle (Nowak 2012)
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