Characterization of the Myxosporean Parasite Isolated from Emaciated Olive Flounders Paralichthys olivaceus on Jeju Island

Abstract

To investigate the causes of emaciation in cultured olive flounder Paralichthys olivaceus in Korea. We performed histological examinations and polymerase chain reaction (PCR) with a new primer set. In most cases, the most severe emaciation was observed in the abdominal area Using PCR on extracted livers, kidneys, spleens, gills, brains, and intestines, we found that areas around the kidneys and intestines were as almost always positive. In significantly emaciated fish, PCR was positive in all internal organs except the gills. In addition, the homology of 812-bp nucleotide sequences of the 28S rRNA gene was more than 99% in emaciated fish. Partial homology with Myxobolus spp. and Cystodiscus axonis, whose data were obtained from GenBank was 86% and 88%, respectively. Histological examinations detected spores in kidneys and intestines but not in other organs. We also performed cohabitation experiments to determine whether infections could be exchanged among species or only within species. Uninfected olive flounder and red sea bream, Pagrus major, cohabitating with emaciated olive flounder showed 100% and 0% cumulative mortality, respectively. Thus the cause of emaciation in cultured olive flounder of Korea is likely due to a new parasite.

Quantitative investigation of Enteromyxum leei (Myxozoa: Myxosporea) infection and relative condition factor in cultured olive flounder Paralichthys olivaceus (Temminck and Schlegel)

“…Since the first detection of emaciation disease in cultured olive flounder of Korea, several studies have been performed to verify its aetiological agent, pathophysiological mechanism and clinical features (Choi et al., ; Kim, Jun, Park, Jeong, & Jeong, ; Kim et al., ; Sekiya et al., ). Interestingly, a Korean research group reported that a Parvicapsula anisocaudata caused emaciation in cultured olive flounder in Korea (Kim et al., ) whereas a Japanese research group identified E. leei as pathogen of the emaciation disease (Sekiya et al., ) even though these two studies investigated olive flounder produced in the same region (Jeju Island). Recently, we revealed that E. leei is a causative agent of emaciation disease in cultured olive flounder using molecular diagnostics (Shin, Sohn, Jin, Kang, & Lee, ).…”

“…The production of fish comprises 50% of finfish culture. Since the first detection of emaciation disease in cultured olive flounder of Korea, several studies have been performed to verify its aetiological agent, pathophysiological mechanism and clinical features (Choi et al, 2012;Kim, Jun, Park, Jeong, & Jeong, 2015;Kim et al, 2011;Sekiya et al, 2016).…”

“…Interestingly, a Korean research group reported that a Parvicapsula anisocaudata caused emaciation in cultured olive flounder in Korea (Kim et al, 2015) whereas a Japanese research group identified E. leei as pathogen of the emaciation disease (Sekiya et al, 2016) even though these two studies investigated olive flounder produced in the same region (Jeju Island). Recently, we revealed that E. leei is a causative agent of emaciation disease in cultured olive flounder gated the parasite intensity in the posterior intestine of the fish.…”

Monitoring of emaciation disease in cultured Paralichthys olivaceus of Jeju island during 2014–2015

“…The death rate of olive flounders occurring within 1-3 weeks after the first symptoms appear is increasing. Fish infected with this illness show darkening of the body color, a decrease in weight, and bleeding (Kim et al 2015). The myxosporean emaciation disease has occurred in tiger puffer (Takifugu rubripes), parrotfish (Sparisoma cretense), and olive flounder (Ishimatsu et al 2007;Katharios et al 2014;Yasuda et al 2005).…”

“…Although external symptoms including abdominal emaciation and body darkening were observed, there is no clear information on exact life cycle has not been reported. In addition, PCR analysis of the olive flounders of Jeju island with the primer set of Enteromyxum leei (1589 bp), an etiologic agent of turbot myxosporean emaciation disease in Japan, a neighboring country of Korea, ruled out E. leei as the etiologic agent, as a negative reaction was observed (Kim et al 2015). We designed the specific primer set for detection of myxosporea from emaciated olive flounder in Korea (Kim et al 2015).…”