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NO53 - 3

Mass Mortality Caused by Pseudomonas anguilliseptica in the Pond-cultured Ayu Plecoglossus altivelis

Yoshiko Shimahara1*, Yasuhiko Kawato2, Ikunari Kiryu3, Toyohiro Nishioka1, Takashi Kamaishi4, Kei Yuasa2, Satoshi Miwa2, Mei Hosaka5, Ryo Matsumoto6, Toshihiro Nakai6 and Norihisa Oseko7

1Kamiura Laboratory, National Research Institute of Aquaculture,
Japan Fisheries Research and Education Agency, Oita 879-2602, Japan

2Nansei Main Station, National Research Institute of Aquaculture,
Japan Fisheries Research and Education Agency, Mie 516-0193, Japan

3Tamaki Laboratory, National Research Institute of Aquaculture,
Japan Fisheries Research and Education Agency, Mie 519-0423, Japan

4Headquarters, Japan Fisheries Research and Education Agency, Kanagawa 220-6115, Japan
5Akita Prefectural Institute of Fisheries, Akita 010-0531, Japan
6Graduate School of Biosphere Science, Hiroshima University, Hiroshima 739-8528, Japan
7Kushiro Laboratory, Hokkaido National Fisheries Research Institute,
Japan Fisheries Research and Education Agency, Hokkaido 085-0802, Japan

(Received February 6, 2018)

ABSTRACT--Pseudomonas anguilliseptica infections have not been reported in cultured ayu Plecoglossus altivelis in Japan since a few occurrences in the 1980s. In the spring of 2013, however, mass mortality was encountered at an ayu rearing facility in Akita Prefecture, Japan, and the causative agent was identified as P. anguilliseptica. In this study, biochemical characterizations and 16S rRNA gene sequences of the isolates from the present event were shown to be identical to previously reported isolates of P. anguilliseptica from ayu. LD50 of the present isolate against ayu in the infection test was 1.7 × 103 cfu/fish.

Key words: Pseudomonas anguilliseptica, Plecoglossus altivelis, 16S rRNA gene, mass mortality, pathogenicity

First Report of Thelohanellus testudineus (Myxosporea) from the Skin of Goldfish Carassius auratus in Japan

Jumpei Arakawa1* and Tohru Mekata2

1Yatomi Station, Freshwater Resources Research Center, Aichi Fisheries Research Institute, Aichi 498-0017, Japan
2Nansei Main Station, National Research Institute of Aquaculture,
Japan Fisheries Research and Education Agency, Mie 516-0193, Japan

(Received February 6, 2018)

ABSTRACT--In 2017, one individual of goldfish Carassius auratus which had tumor-like massive lesions in the skin was found in a goldfish wholesale market in Aichi Prefecture, Japan. The lesions were 2-4 mm in diameter and hemorrhage was observed in some of them. Microscopic observation revealed numerous myxospores with a single polar capsule. The spores were 17.1 ± 1.0 μm (mean ± SD) long, and 6.1 ± 0.7 μm wide. The partial sequence of 18S rRNA gene was 100% identical to that of Thelohanellus testudineus. This is the first report of T. testudineus in goldfish.

Key words: Thelohanellus testudineus, myxospore, Carassius auratus, goldfish

An Oral Vaccination Method with the Aid of Capsaicin against Viral Nervous Necrosis (VNN)

Alkhateib Y. Gaafar1, Hirofumi Yamashita2, Indah Istiqomah3, Yasuhiko Kawato4, Kanae Ninomiya5, Abd Elgayed Younes1 and Toshihiro Nakai5*

1Veterinary Research Division, National Research Centre, Giza 12622, Egypt
2Ehime Research Institute of Agriculture, Forestry and Fisheries, Ehime 798-0104, Japan
3Department of Fisheries, Faculty of Agriculture, Gadjah Mada University, Yogyakarta 55281, Indonesia
4Nansei Main Station, National Research Institute of Aquaculture,
Japan Fisheries Research and Education Agency, Mie 516-0193, Japan

5Graduate School of Biosphere Science, Hiroshima University, Hiroshima 739-8528, Japan

(Received March 22, 2018)

ABSTRACT--To develop an oral vaccination method for viral nervous necrosis (VNN) caused by piscine nodavirus (betanodavirus), sevenband grouper Epinephelus septemfasciatus was immunized with inactivated redspotted grouper nervous necrosis virus (RGNNV) vaccine. Seven-day consecutive oral administration of the RGNNV vaccine via feed failed to induce protection in fish against the virus challenge at 21 days post-immunization. However, anal intubation of the vaccine conferred protective immunity on fish, although virus neutralizing antibodies could not be detected. Similar protective immunity was also confirmed by oral administration of vaccine via feed supplemented with capsaicin, suggesting that capsaicin modulated the intestinal mucosal barrier to induce immune response.

Key words: viral nervous necrosis, betanodavirus, oral vaccination, capsaicin, Epinephelus septemfasciatus