Amoebic gill disease outbreak in marine fish cultured in Korea

Abstract

Brief CommunicationAmoebic gill disease (AGD) is a serious parasitic disease that affects marine cultured salmonids including Atlantic salmon (Salmo salar), coho salmon (Oncorhynchus kisutch), and rainbow trout (Oncorhynchus mykiss) in Australia, the United States, and several European countries. 7-10 AGD also affects other fish species cultured in marine environments, including turbot (Psetta maxima; syn. Scophthalmus maximus), European seabass (Dicentrarchus labrax), sharpsnout seabream (Diplodus puntazzo), ballan wrasse (Labrus bergylta), and ayu (Plecoglossus altivelis) in Spain, South Africa, the Mediterranean, Norway, and Japan. [1][2][3][7][8][9] Thus, AGD threatens the marine farming industry in many countries.The clinical signs of AGD include multiple white-to-gray patches on swollen gills, with excess mucus surrounding gill arches. 7 The main histologic feature of AGD is prominent epithelial hyperplasia in the gills, resulting in complete lamellar fusion. 7,10 Neoparamoeba perurans, Neoparamoeba pemaquidensis, and Neoparamoeba branchiphila have been isolated from or detected in marine fish with AGD. 7,9 Of these amoebae, N. perurans is known as a cosmopolitan etiologic agent of AGD. 14 AGD had not been reported in marine fish in far east Asia until 1994. In 1995, amoebic infection was reported in cultured olive flounder (syn. Japanese flounder; Paralichthys olivaceus) in Korea. 4 Since then, AGD has been found in cultured ayu in 2008 in Japan 1 and coho salmon in 2014 in Korea. 6 We report herein amoebic infection in the following 3 new marine fish species that are cultured in Korea: black seabream (syn. black porgy; Acanthopagrus schlegelii), rock bream (syn. barred knifejaw; Oplegnathus fasciatus), and gray mullet (syn. flathead mullet; Mugil cephalus).In 2015, 6.7-60% mortality was observed in black seabream, rock bream, and mullet farmed on the southern coast of Korea. Black seabream and rock bream were cultured in a farm (land-based system) located in Goheung County. Gray mullet were cultured in a farm (net cage system) located in Hadong County. A total of 21 diseased fish (10 black seabream, weight: 119 ± 29 g; 7 rock bream, 62 ± 23 g; and 4 mullet, 128 ± 23 g) were collected and individually subjected to parasitologic, bacteriologic, and virologic examinations. Gills and body surface were microscopically examined for parasites. Kidney, spleen, and liver were cultured on brainheart infusion agar a plates supplemented with 1% NaCl and incubated at 15°C for 14 d. Kidney and spleen samples were homogenized in 10 volumes of Hanks balanced salt solution b and centrifuged at 3,000 × g for 20 min. The supernatant was filtered through a 450-nm membrane filter. One-hundred microliters of the filtrate was inoculated onto Chinook salmon embryo (CHSE-214) and fathead minnow (FHM) cells in Abstract. In 2015, 6.7-60% mortality was observed in black seabream (Acanthopagrus schlegelii), rock bream (Oplegnathus fasciatus), and gray mullet (Mugil cephalus) farmed in the southern coast of Korea. On examination, num...

The gill parasite Paramoeba perurans compromises aerobic scope, swimming capacity and ion balance in Atlantic salmon

“…P. perurans has so far been documented in at least 17 fish species ( Oldham et al , 2016 ; Kim et al , 2017 ), however, little is currently known about the pathological consequence in non-salmonids or whether certain species are more susceptible to AGD compared to others. If wild fish develop disease, this may be difficult to observe since infected fish are less likely to survive and get caught by a researcher.…”

“…Paramoeba perurans is a cosmopolitan ectoparasite and an aetiological agent of amoebic gill disease (AGD); a serious problem in salmonid aquaculture globally ( Munday et al , 2001 ; Young et al , 2008 ; Mitchell and Rodger, 2011 ). Although AGD in farmed Atlantic salmon has been the focus of previous studies, P. perurans do not elicit a clear host specificity, and currently infections in 17 species from 14 different genera has been documented ( Oldham et al , 2016 ; Kim et al , 2017 ).…”

Repeated sublethal freshwater exposures reduce the amoebic gill disease parasite, Neoparamoeba perurans, on Atlantic salmon

“…AGD outbreaks are most effectively controlled using freshwater bathing treatments. This is suitable for eight of the 16 AGD‐affected fish species used in mariculture which are freshwater tolerant (ayu Plecoglossus altivelis , sea bass Dicentrarchus labrax , flathead grey mullet Mugil cephalus and five salmonid species) (Froese & Pauly, ; Kim, Kong, Kim, Jung, & Oh, ; Oldham et al., ). However, freshwater bathing is expensive and difficult to apply in areas where freshwater access is limited (Munday, Zilberg, & Findlay, ; Rodger, ).…”

Immersion challenge of naïve Atlantic salmon with cultured Nolandella sp. and Pseudoparamoeba sp. did not increase the severity of Neoparamoeba perurans‐induced amoebic gill disease (AGD)

“…Paramoeba perurans ), causes amoebic gill disease (AGD) which increasingly impedes the marine phase of salmonid aquaculture globally (Oldham et al., 2016). This aetiological link is supported by both the fulfilment of Koch's postulates (Crosbie et al., 2012) and the consistent association of N. perurans with branchitis across various fish hosts and locations (Karlsbakk et al., 2013; Kim et al., 2017; Young et al., 2008). Attachment of N. perurans to gills causes epithelial hyperplasia, lamellar fusion, oedema and ultimately mortality if not treated (Munday et al., 2001).…”