The induction of laboratory‐based amoebic gill disease revisited

Morrison, Richard N.; Crosbie, Philip; Nowak, Barbara F.

doi:10.1111/j.1365-2761.2004.00561.x

Cited by 89 publications

(76 citation statements)

References 7 publications

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“…The gross gill scoring, histological scoring and in particular the molecular data presented showed that detection of N. perurans was possible within 2weeks post-infection and has been previously reported (Morrison et al, 2004;Taylor et al, 2007). Histological examination of the samples in this study identified pathological changes within the first week; however the observation of amoeba in the presence of pathology and therefore case definition was not confirmed by histology until the second week.…”

Section: Discussionmentioning

confidence: 46%

“…In order to conduct an infection trial for the comparison of the preferred assay with traditional screening methods, N. perurans was isolated from farmed Atlantic salmon affected by AGD in the west of Ireland using a method described in Downes et al (2015), adapted from Morrison et al (2004). The amoeba culture was established and maintained according to Crosbie et al (2012).…”

Section: Amoebae Culturementioning

confidence: 99%

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Evaluation of Non-destructive Molecular Diagnostics for the Detection of Neoparamoeba perurans

et al. 2017

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Amoebic gill disease (AGD) caused by Neoparamoeba perurans, has emerged in Europe as a significant problem for the Atlantic salmon farming industry. Gross gill score is the most widely used and practical method for determining AGD severity on farms and informing management decisions on disease mitigation strategies. As molecular diagnosis of AGD remains a high priority for much of the international salmon farming industry, there is a need to evaluate the suitability of currently available molecular assays in conjunction with the most appropriate non-destructive sampling methodology. The aims of this study were to assess a non-destructive sampling methodology (gill swabs) and to compare a range of currently available real-time polymerase chain-reaction (PCR) assays for the detection of N. perurans. Furthermore a comparison of the nondestructive molecular diagnostics with traditional screening methods of gill scoring and histopathology was also undertaken. The study found that all molecular protocols assessed performed well in cases of clinical AGD with high gill scores. A TaqMan based assay (protocol 1) was the optimal assay based on a range of parameters including % positive samples from a field trial performed on fish with gill scores ranging from 0 to 5. A higher proportion of gill swab samples tested positive by all protocols than gill filament biopsies and there was a strong correlation between gill swabs tested by protocol 1 and gross gill score and histology scores. Screening for N. perurans using protocol 1 in conjunction with non-destructive gill swab samples was shown to give the best results.

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Section: Discussionmentioning

confidence: 46%

Section: Amoebae Culturementioning

confidence: 99%

Evaluation of Non-destructive Molecular Diagnostics for the Detection of Neoparamoeba perurans

et al. 2017

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“…Briefly, AGD had been maintained in this tank for several months, with introduced fish exhibiting gross signs of AGD within 3 d of cohabitation. The presence of Neoparamoeba pemaquidensis, the putative agent of AGD, was routinely confirmed using a modified indirect fluorescent antibody test (Roberts & Powell 2003b), PCR (Wong et al 2004), immunohistochemistry (Bridle et al 2003 and by visually identifying parasomes within isolated gill amoebae (Morrison et al 2004). All fish were fed to satiation daily with non-medicated pellets, and further lethally sampled 3 and 5 d into their cohabitation with AGD-affected fish.…”

Section: Methodsmentioning

confidence: 99%

Oral l-cysteine ethyl ester (LCEE) reduces amoebic gill disease (AGD) in Atlantic salmon Salmo salar

Roberts

Powell²

2005

Dis. Aquat. Org.

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There is a need for the development of alternative therapeutic treatments for amoebic gill disease (AGD) in Atlantic salmon Salmo salar L. to maintain the sustainability of the Tasmanian Atlantic salmon aquaculture industry. This study aimed to assess the effects of the mucolytic drug L-cysteine ethyl ester (LCEE) on marine Atlantic salmon mucus and whether or not it may have a therapeutic advantage for the alleviation of AGD when administered orally. We also aimed to document any physiological consequences of LCEE. Results showed that LCEE significantly decreased the viscosity of marine Atlantic salmon mucus both in vitro, where LCEE concentration showed a negative relationship to mucus viscosity (R 2 = 0.95 at 11.5 s -1 ), and in vivo. Oral administration of LCEE at 52.7 mg LCEE kg -1 fish d -1 over 2 wk significantly delayed the progression of AGDassociated pathology during an aggressive, cohabitation induced, laboratory infection. Medicated fish had approximately 50% less gill filaments affected by AGD than control fed fish at 3 d postinfection when assessed using histology. Palatability of medicated feed was shown to be approximately 65% of control feed. No osmoregulatory disturbance was seen in medicated fish, although blood and whole body flux data indicated a slight acidosis coinciding with an increased plasma total ammonia concentration. However, both variables were within a tolerable physiological range and returned to control levels 3 d post-cessation of medicated feed. LCEE holds potential as an in-feed additive when administered over 2 wk prior to infection to delay the progression of AGD associated pathology. From the parameters measured, LCEE seems to have minimal physiological consequences after 2 wk of administration. KEY WORDS: Fish gill disease · Salmonid · In-feed treatment · Oral therapeutant · Mucolytic drug · Mucus viscosity · Physiological effects Resale or republication not permitted without written consent of the publisherDis Aquat Org 66: [21][22][23][24][25][26][27][28] 2005 Roberts & Powell 2003a). It has been previously suggested that excessive branchial mucus impairs CO 2 excretion, leading to respiratory acidosis and subsequent death in AGD affected fish (Powell et al. 2000). The break-up and removal of mucus from the gills seems to be an important function of freshwater bathing as a treatment . Indeed, freshwater bathing has been shown to significantly decrease mucus viscosity of marine Atlantic salmon (Roberts 2004). Thinner and more removable mucus is thought to aid the significant lesion fragmentation and shedding of AGD lesion-associated hyperplastic gill tissue, as well as sloughing of gill-associated amoebae in soft, freshwater-bathed fish (Roberts & Powell 2003b).Therapeutic mucolytic drugs have been extensively used for the alleviation of respiratory diseases associated with excessive production and accumulation of mucus in humans and domestic animals. N-acetylcysteine (NAC) is a widely used mucolytic agent that by virtue of its free sulfhydryl group reacts w...

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“…Neoparamoeba sp. were harvested from the AGD affected Atlantic salmon held in the Aquaculture Centre, University of Tasmania, Launceston by a method described by Morrison et al (2004). In brief, infected gills were removed from AGD affected Atlantic salmon after euthanasia (anaesthetic overdose at 20 ml l -1 Aqui-S ® ).…”

Section: Resale or Republication Not Permitted Without Written Consenmentioning

confidence: 99%

“…Until now AGD infection has always been established by cohabiting naïve fish with infected fish (Howard et al 1993, Akhlaghi et al 1996, or by exposing fish to isolated, gill-associated Neoparamoeba sp. , Morrison et al 2004, Morrison et al 2005 as the disease cannot be reproduced using cultured organisms (Kent et al 1988, Howard et al 1993, Findlay et al 2000, Morrison et al 2005.…”

Section: Introductionmentioning

confidence: 99%

Influence of salmonid gill bacteria on development and severity of amoebic gill disease

Embar-Gopinath¹,

Bütler²,

Nowak³

2005

Dis. Aquat. Org.

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ABSTRACT:The relationship between salmonid gill bacteria and Neoparamoeba sp., the aetiological agent of amoebic gill disease (AGD) was determined in vivo. Fish were divided into 4 groups and were subjected to following experimental infections: Group 1, amoebae only; Group 2, Staphylococcus sp. and amoebae; Group 3, Winogradskyella sp. and amoebae; Group 4, no treatment (control). Fish (Groups 1, 2 and 3) were exposed to potassium permanganate to remove the natural gill microflora prior to either bacterial or amoebae exposure. AGD severity was quantified by histological analysis of gill sections to determine the percentage of lesioned filaments and the number of affected lamellae within each lesion. All amoebae infected groups developed AGD, with fish in Group 3 showing significantly more filaments with lesions than other groups. Typically lesion size averaged between 2 to 4 interlamellar units in all AGD infected groups. The results suggest that the ability of Neoparamoeba sp. to infect filaments and cause lesions might be enhanced in the presence of Winogradskyella sp. The possibility is proposed that the prevalence of more severe AGD is due to the occurrence of Winogradskyella sp. at high concentrations on the gills.KEY WORDS: Neoparamoeba · Winogradskyella · AGD · Potassium permanganate · Protozoan diseases · Salmon diseases · Amoeba · Bacteria Resale or republication not permitted without written consent of the publisherDis Aquat Org 67: [55][56][57][58][59][60] 2005 MATERIALS AND METHODS Fish. Atlantic salmon Salmo salar L. (n = 72; mean weight = 88 g) were acclimatised to sea water (35 ‰, 1 µm filtered) over a week in 6 identical recirculating systems each consisting of three 70 l tanks (n = 4 fish per tank) and a 70 l reservoir. A sentinel population (n = 12) of the same body weight was acclimatised in a static tank (210 l). Following acclimatisation, fish in the recirculating systems were divided into 3 treatment groups (n = 12 fish per treatment). Each treatment was duplicated. The 4th group was the sentinel population (n = 12). Fish in Group 1 were exposed to amoebae only (positive control); Group 2, Gram positive bacteria (Staphylococcus sp.) and amoebae; Group 3, Gram negative bacteria (Winogradskyella sp.) and amoebae; Group 4 did not receive any treatment. Sea water temperature was maintained at 16 ± 0.5°C, pH 8.2, dissolved oxygen 7.6 mg l -1 , salinity 35 ‰ and total ammonia-nitrogen below 0.2 mg l -1 . Sufficient air supply was maintained in the tanks throughout the experiment by using aerators.Neoparamoeba sp. isolation. Neoparamoeba sp. were harvested from the AGD affected Atlantic salmon held in the Aquaculture Centre, University of Tasmania, Launceston by a method described by Morrison et al. (2004). In brief, infected gills were removed from AGD affected Atlantic salmon after euthanasia (anaesthetic overdose at 20 ml l -1 Aqui-S ® ). Gills were transported to the laboratory in sterile sea water (SS) containing antibiotic and antimycotic solution (5% v/v 5000 IU ml -1 penicillin and 5 mg...

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The induction of laboratory‐based amoebic gill disease revisited

Cited by 89 publications

References 7 publications

Evaluation of Non-destructive Molecular Diagnostics for the Detection of Neoparamoeba perurans

Evaluation of Non-destructive Molecular Diagnostics for the Detection of Neoparamoeba perurans

Oral l-cysteine ethyl ester (LCEE) reduces amoebic gill disease (AGD) in Atlantic salmon Salmo salar

Influence of salmonid gill bacteria on development and severity of amoebic gill disease

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