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Diseases of Aquatic Organisms

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DAO 150:31-36 (2022)  -  DOI: https://doi.org/10.3354/dao03672

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Epitheliocystis caused by a novel Chlamydia emerging in Spinibarbus denticulatus in China

Fan Liu1,#, Yang Feng1,#, Yi Geng1,*, Defang Chen2, Ping Ou Yang1, Xiaoli Huang2, Hongrui Guo1, Zhicai Zuo1, Huidan Deng1, Jin Fang1

1College of Veterinary Medicine, Sichuan Agricultural University, Chengdu, Sichuan 611130, PR China
2Department of Aquaculture, Sichuan Agricultural University, Chengdu, Sichuan 611130, PR China
*Corresponding author:
#These authors contributed equally

ABSTRACT: Epitheliocystis is an emerging and global aquaculture disease caused by a diverse range of bacteria of the order Chlamydiales. Here we report a case of epitheliocystis caused by a novel Chlamydia bacterium, which resulted in 40% mortality in cultured cyprinids (Spinibarbus denticulatus). The affected fish exhibited lethargy, were observed swimming near the oxygen pump and subsequently died. Histopathology analysis revealed that lesions were concentrated mainly on the gills. The epithelial cells of the damaged gill lamellae showed hyperplasia, fusion and adhesion, and were characterized by inflammation and necrosis. Inclusion bodies were observed in some proliferating epithelial cells at the tips of the gill lamellae and were accompanied by different degrees of mucous cell proliferation. Transmission electron microscopy examination clearly showed the morphological characteristics of chlamydia-like bacteria in epithelial cells. In addition, 16S rRNA sequencing (752 bp) and molecular phylogenetic analyses revealed that epitheliocystis agents detected in S. denticulatus belonged to a novel family, Chlamydiaceae. This is the first report of epitheliocystis in cultured fish in China, and the findings in this study increase the range of hosts affected by epitheliocystis.


KEY WORDS: Chlamydiae · Epitheliocystis · Pathologic lesion · Phylogenetic analysis · Spinibarbus denticulatus


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Cite this article as: Liu F, Feng Y, Geng Y, Chen D and others (2022) Epitheliocystis caused by a novel Chlamydia emerging in Spinibarbus denticulatus in China. Dis Aquat Org 150:31-36. https://doi.org/10.3354/dao03672

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