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NO54 - 1

Worm Cataract of Hatchery-Reared Japanese Dace Tribolodon hakonensis Caused by Diplostomum sp. (Digenea: Diplostomidae)

Norihiko Komatsu1*, Naoki Itoh2 and Kazuo Ogawa3

1Suwa Branch, Nagano Prefectural Fisheries Experimental Station, Nagano 393-0034, Japan
2Laboratory of Fish Diseases, the University of Tokyo, Tokyo 113-8657, Japan
3Meguro Parasitological Museum, Tokyo 153-0064, Japan

(Received September 12, 2018)

ABSTRACT--In 2015, cataract was observed in juvenile Japanese dace Tribolodon hakonensis, reared in a hatchery in Nagano Prefecture, Japan. Metacercariae were found in the lens, with the prevalence and mean intensity of infection of dace (0.5-2.4 g in body weight) reaching 100% and 39.7, respectively, in the most heavily infected fish group. Histologically, the lens became partially fragmented around the metacercariae, which occupied a considerable space, surrounded by their own excreta. Among snails sampled from outdoor ponds and waterways, cercariae with a bifurcated tail were found in the lymnaeid, Radix auricularia japonica. ITS1-5.8S-ITS2 and cytochrome oxidase subunit I (COI) sequences of metacercariae from the lens of dace and cercariae from the lymnaeid were nearly identical to each other, indicating that the lymnaeid is the first and dace is the second intermediate host. However, since the obtained COI gene sequences were close but not identical to known Diplostomum spp., this species was not identified to the species level. The morphology of metacercaria was also described. This is the second reported case of worm cataract in fish caused by Diplostomum metacercariae in Japan

Key words: worm cataract, Diplostomum, metacercaria, Tribolodon hakonensis, Japanese dace, seed production

Streptococcus Infections in Cultured Pond Loach Paramisgurnus dabryanus in China

Zhang Luo1,a, Xiao Hui Bai1,a, Zhen Guo Zhang1, Shuang Hao1, Wen Ping Jia1, Jin Lan Liu2, Peng Shao2, Wen Li Zhou2 and Shou Ming Feng1,3*

1Tianjin Fishery Research Institute, Tianjin 300221, P. R. China
2College of Fisheries, Tianjin Agricultural University, Tianjin 300384, P. R. China
3Prevention and Cure Center for Aquatic Animal Disease in Tianjin, Tianjin 300221, P. R. China

(Received October 22, 2018)

ABSTRACT--In 2017, high mortalities were observed in cultured pond loach Paramisgurnus dabryanus in Tianjin, China. The symptoms observed in the moribund loach included hemorrhage on the body surface and head, exophthalmos, and erratic swimming around the water surface. Two different Gram-positive bacteria were isolated from the diseased loach in two different fish farms. They were identified as Streptococcus dysgalactiae and Streptococcus agalactiae, using 16S rRNA gene sequencing and biochemical characterization. The median lethal doses of the bacterial strains in the loach were 3.2 × 105 and 5.0 × 105 CFU/fish, respectively.

Key words: Paramisgurnus dabryanus, pond loach, streptococcosis, Streptococcus dysgalactiae,

Isolation of Nervous Necrosis Virus from Hybrid Grouper (Epinephelus fuscoguttatus♀ × Epinephelus lanceolatus♂) Cultured in Guangxi, China

Qing Yu1,a, Mingzhu Liu1,a, Shina Wei2,a, Hehe Xiao5, Siting Wu3, Xianling Qin4, Deqiang Shi1, Siqiao Li1, Taixia Wang5 and Pengfei Li1*

1Guangxi Key Laboratory of Marine Natural Products and Combinatorial Biosynthesis Chemistry, Guangxi Academy of Sciences, Nanning 530007, P. R. China
2College of Marine Sciences, South China Agricultural University, Guangzhou 510642, P. R. China 3Guangxi Key Lab for Marine Biotechnology, Guangxi Institute of Oceanography, Beihai 536000, P. R. China
4Key Laboratory of Marine Environmental Science, Guangxi Academy of Sciences, Nanning 530007, P. R. China
5,/sup>College of Life Science, Henan Normal University, Xinxiang 453007, P. R. China

(Received December 26, 2018)

ABSTRACT--Outbreaks of suspected viral nervous necrosis emerged in cultured groupers in Guangxi, China in August 2018. Histopathology showed severe vacuolation in the brain tissue of the diseased juvenile hybrid grouper (Epinephelus fuscoguttatus♀ × Epinephelus lanceolatus♂). A nervous necrosis virus (NNV) was isolated from pooled sample of the brain and eyes using a grouper cell line EAGB. Cytopathic effect with multiple cytoplasmic vacuolation cells developed in EAGB cells. The coat protein gene sequence of the isolate (GNNV-Gx) showed that it belonged to RGNNV genotype and was most closely related to that of a tiger grouper NNV registered in GenBank. The infectivity of the isolate decreased remarkably at pH 3 and pH 10 and was susceptible to 60°C.

Key words: VNN, grouper NNV, hybrid grouper

Detection of Erythrocytic Inclusion Body Syndrome (EIBS) Virus (Piscine orthoreovirus 2) from Ovarian Fluid of Coho Salmon Survivor

Norihiko Komatsu1*, Naoki Itoh2 and Kazuo Ogawa3

Akira Kumagai1*, Tomokazu Takano2, Tomomasa Matsuyama2, Takamitsu Sakai3, Yuki Nochiri4, Ryo Honda4, Takumi Kikuta1 and Miho Honjo1

(Received December 26, 2018)

ABSTRACT--Mortality of farmed coho salmon Oncorhynchus kisutch due to erythrocytic inclusion body syndrome (EIBS) has been posing severe economic losses in Japan since 1986. The etiologic agent of EIBS was reported to be piscine orthoreovirus 2 (PRV-2). We detected PRV-2 in the ovarian fluid samples of 10% of EIBS-experienced spawners (n = 30) by RT-PCR. When each of 30 individual ovarian fluid samples was inoculated into a naïve coho salmon, 37% of the blood samples from the fish tested positive for PRV-2 at 20 days post injection. These observations suggest that the ovarian fluid of EIBS-experienced fish can be contaminated with the infective viral particles of PRV-2.

Key words: erythrocytic inclusion body syndrome, piscine orthoreovirus 2, ovarian fluid, coho salmon