First record of amoebic gill disease caused by N eoparamoeba perurans in S outh A frica

A relationship between increasing water temperature and amoebic gill disease (AGD) prevalence in Atlantic salmon (Salmo salar) has been noted at fish farms in numerous countries. In Scotland (UK), temperatures above 12°C are considered to be an important risk factor for AGD outbreaks. Thus, the purpose of this study was to test for the presence of an association between temperature and variation in the severity of AGD in Atlantic salmon at 10 and 15°C. The results showed an association between temperature and variation in AGD severity in salmon from analysis of histopathology and Paramoeba perurans load, reflecting an earlier and stronger infection post‐amoebae exposure at the higher temperature. While no significant difference between the two temperature treatment groups was found in plasma cortisol levels, both glucose and lactate levels increased when gill pathology was evident at both temperatures. Expression analysis of immune‐ and stress‐related genes showed more modulation in gills than in head kidney, revealing an organ‐specific response and an interplay between temperature and infection. In conclusion, temperature may not only affect the host response, but perhaps also favour higher attachment/growth capacity of the amoebae as seen with the earlier and stronger P. perurans infection at 15°C.

Section: Discussionmentioning

confidence: 96%

Effects of temperature on amoebic gill disease development: Does it play a role?

Benedicenti

Pottinger

Collins

et al. 2019

“…; Mitchell & Rodger ; Mouton et al . ). In addition, P. perurans is also believed to be responsible for gill disease in turbot, Scophthalmus maximus (L.), European sea‐bass, Dicentrarchus labrax (L.), sharp snout sea bream, Diplodus puntazzo (Walbaum), ayu, Plecoglossus altivelis (Temminck & Schlegel), blue warehou, Seriolella brama Günther, olive flounder, Paralichthys olivaceus (Temminck & Schlegel) and recently in ballan wrasse, Labrus bergylta Ascanius (Dyková & Novoa ; Dyková et al .…”

Section: Introductionmentioning

confidence: 97%

Morphological diversity of Paramoeba perurans trophozoites and their interaction with Atlantic salmon, Salmo salar L., gills

Wiik‐Nielsen

Kolstad

et al. 2016

Amoebic gill disease (AGD) caused by the ectoparasite Paramoeba perurans affects several cultured marine fish species worldwide. In this study, the morphology and ultrastructure of P. perurans in vitro and in vivo was investigated using scanning and transmission electron microscopy (SEM and TEM, respectively). Amoebae cultures contained several different morphologies ranging from a distinct rounded cell structure and polymorphic cells with pseudopodia of different lengths and shapes. SEM studies of the gills of AGD-affected Atlantic salmon, Salmo salar L., revealed the presence of enlarged swellings in affected gill filaments and fusion of adjacent lamellae. Spherical amoebae appeared to embed within the epithelium, and subsequently leave hemispherical indentations with visible fenestrations in the basolateral surface following their departure. These fenestrated structures corresponded to the presence of pseudopodia which could be seen by TEM to penetrate into the epithelium. The membrane-membrane interface contained an amorphous and slightly fibrous matrix. This suggests the existence of cellular glycocalyces and a role for extracellular products in mediating pathological changes in amoebic gill disease.

“…; Nowak ; Mouton et al . ; Rodger ). Salmon suffering from AGD show multifocal lesions that appear as pale gill tissue, or white mucoid spots and plaques, together with clinical signs such as flared opercula, respiratory distress and lethargy (Rodger & Mcardle ; Munday, Zilberg & Findlay ).…”

Section: Introductionmentioning

confidence: 99%

PCR survey for Paramoeba perurans in fauna, environmental samples and fish associated with marine farming sites for Atlantic salmon (Salmo salar L.)

Hellebø

Stene

Aspehaug

2016

Amoebic gill disease (AGD) caused by the amoeba Paramoeba perurans is an increasing problem in Atlantic salmon aquaculture. In the present PCR survey, the focus was to identify reservoir species or environmental samples where P. perurans could be present throughout the year, regardless of the infection status in farmed Atlantic salmon. A total of 1200 samples were collected at or in the proximity to farming sites with AGD, or with history of AGD, and analysed for the presence of P. perurans. No results supported biofouling organisms, salmon lice, biofilm or sediment to maintain P. perurans. However, during clinical AGD in Atlantic salmon, the amoeba were detected in several samples, including water, biofilm, plankton, several filter feeders and wild fish. It is likely that some of these samples were positive as a result of the continuous exposure through water. Positive wild fish may contribute to the spread of P. perurans. Cleaner fish tested positive for P. perurans when salmon tested negative, indicating that they may withhold the amoeba longer than salmon. The results demonstrate the high infection pressure produced from an AGD-afflicted Atlantic salmon population and thus the importance of early intervention to reduce infection pressure and horizontal spread of P. perurans within farms.