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Diseases of Aquatic Organisms

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DAO 154:59-68 (2022)  -  DOI:

Outbreak of Cryptocaryon irritans infection in silver pomfret Pampus argenteus cultured in China

Kejing Huang1, Xionglin Li1, Xinyuan Yue1, Hao Cui1, Wenlian Huang1, Rongrong Ma1,2, Jianhu Jiang3, Shan Jin1,2, Yajun Wang1,2, Jiasong Xie1,2,*

1School of Marine Sciences, Ningbo University, Ningbo, Zhejiang 315211, PR China
2Key Laboratory of Aquacultural Biotechnology, Ministry of Education, Ningbo University, Ningbo, Zhejiang 315211, PR China
3Zhejiang Institute of Freshwater Fisheries, Huzhou, Zhejiang 313002, PR China
*Corresponding author:

ABSTRACT: Silver pomfret Pampus argenteus is a major cultivated marine fish species with a high market value. In summer 2021, Cryptocaryon irritans, a ciliate parasite, infected the cultured silver pomfret in aquaculture ponds in Ningbo, Zhejiang Province, China. The symptoms of infected fish include white spots on the skin and fins, increased body surface mucus, loss of appetite, irritability, and shedding of scales. After collecting white spots from moribund fish, the 18S ribosomal RNA sequence of the pathogen on the fish skin was amplified by PCR; phylogenetic analysis showed that it was closely related to C. irritans strains from Ningde, Fujian, China. Four groups of silver pomfret were tested in an artificial infection experiment over the course of 72 h, consisting of 3 infected groups (1600, 4000, and 8000 theronts fish-1) and 1 healthy group. White spots were observed on the skin and fins of the infected fish, but not on their gills. Samples were taken from the gills, liver, kidney, and spleen of both infected and healthy fish and were compared to evaluate any significant histopathological differences. As the dose of infection increased, symptoms became more pronounced. At 72 h, mortality rates were 8.3, 50, and 66.7% for the 3 different concentrations, respectively. The median lethal concentration was calculated to be 366 theronts g-1 at 72 h, 298 theronts g-1 at 84 h, and 219 theronts g-1 at 96 h. This study emphasizes the importance of developing early diagnosis methods and appropriate prevention strategies to decrease the impact of C. irritans infection in the silver pomfret aquaculture industry.

KEY WORDS: Pampus argenteus · Silver pomfret · Cryptocaryon irritans · Parasite · White spot disease

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Cite this article as: Huang K, Li X, Yue X, Cui H and others (2022) Outbreak of Cryptocaryon irritans infection in silver pomfret Pampus argenteus cultured in China. Dis Aquat Org 154:59-68.

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