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NO47 - 3

Curative and Preventive Measures for Edema in Juvenile Japanese Char Salvelinus leucomaenis

Takanori Ishikawa1, Hidenori Ubukata2, Nobuhiro Mano2*, Hitomi Hirose2 and Teruyuki Nakanishi3
1Tochigi Prefectural Fisheries Experimental Station, Tochigi 324-0404, Japan
2Department of Marine Science and Resources, College of Bioresource Sciences, Nihon University, Kanagawa 252-0880, Japan
3Department of Veterinary Medicine, College of Bioresource Sciences, Nihon University, Kanagawa 252-0880, Japan

(Received August 29, 2011)

ABSTRACT―Mortality associated with edema occurred in juvenile Japanese char Salvelinus leucomaenis. Scanning electron microscopy of gill surfaces and histological observations of the gills and kidneys of diseased juveniles indicated that the present pathological changes of the edema disease in juvenile Japanese char (EJJC) were similar to those of the previous study. We conducted three experiments to investigate curative and preventive measures for EJJC: a bath treatment with 1.0% salt water for a curative effect in the early stage of the disease, supplementation of ascorbic acid to the commercial diet (10,000 mg/kg diet) for prevention of the disease, and the supplementation of ascorbic acid along with increased water flow to improve the water quality also for the disease prevention. Results confirmed the curative effect of a 1.0% salt water bath treatment on the early stage of an EJJC outbreak, and the preventive effect on the dietary supplement of ascorbic acid with increasing water quantity before an outbreak.

Key words: ascorbic acid, edema, Salvelinus leucomaenis, Japanese char, salt water bath

Effective Procedures for Culture Isolation of Koi Herpesvirus (KHV)

Kei Yuasa1*, Motohiko Sano2 and Norihisa Oseko1
1National Research Institute of Aquaculture, Fisheries Research Agency, Mie 516-0193, Japan
2National Research Institute of Fisheries Science, Fisheries Research Agency,
Kanagawa 236-8648, Japan

(Received December 16, 2011)

ABSTRACT―Isolation of pathogens is essential for studies on infectious diseases. Present study aimed to develop an effective method for culture isolation of koi herpesvirus (KHV). KHV was effectively isolated using CCB cells only from fish with clinical signs. KHV survived longer at 4°C or -30°C than at 23°C in fish tissues. These results suggest that KHV can be isolated from symptomatic fish kept at the low temperature. To increase isolation efficiencies, the brain as well as the gills and kidney should be included in target organs for examination. In addition, freezing of the organs at -30°C or -85°C is recommended when samples are preserved for a long period before isolation.

Key words: virus isolation, koi herpesvirus, KHV, CCB, sensitivity

In situ Hybridization Detection of Koi Herpesvirus in Paraffin-embedded Tissues of Common Carp Cyprinus carpio Collected in 1998 in Korea

Nam-Sil Lee1, Sung Hee Jung1, Jeong Woo Park2 and Jeong Wan Do1*
1Division of Pathology, National Fisheries Research and Development Institute, Busan 619-705, South Korea
2Department of Biological Sciences, University of Ulsan, Ulsan 680-749, South Korea

(Received April 17, 2012)

ABSTRACT―In Korea, mass mortalities occurred among cultured common carp Cyprinus carpio in 1998. Moribund fish showed clinical signs like those of koi herpesvirus (KHV) disease. In this study, we applied in situ hybridization (ISH) method to detect KHV DNA in paraffin-embedded tissue specimens that had been prepared from the moribund carp of nine fish farms at four different regions in 1998. ISH-positive cells were found in various tissues including kidney, spleen, heart, liver, gills and intestine from eight fish farms. Our results suggest that the mass mortality of carp in 1998 was associated with KHV infection and thus KHV was introduced into fish culture farms in South Korea in 1998 or earlier.

Key words: koi herpesvirus, KHV, CyHV-3, in situ hybridization, Cyprinus carpio

Toxicity of Poly(I:C) against Japanese Flounder Paralichthys olivaceus

Takanori Matsui, Myung-Joo Oh and Toyohiko Nishizawa*
Department of Aqualife Medicine, Chonnam National University, Yeosu 550-749, Republic of Korea

(Received April 25, 2012)

ABSTRACT―We evaluated the effect of rearing temperature (13 and 17°C) on the toxicity of Poly(I:C) against Japanese flounder Paralichthys olivaceus (mean BW 8.2 g). In the fish reared at 17°C, we observed signs of toxicity such as redness or ulceration of the skin around the inoculation site or death in 41.7%, 16.7%, 16.7% and 0% of the fish injected with 800, 400, 200 and 100 mg Poly(I:C)/fish, respectively. In the fish reared at 13°C, we observed signs of toxicity in 83.3%, 75.0%, 25.0% and 33.3% of the fish that were injected with 800, 400, 200 and 100 mg Poly(I:C)/fish, respectively. Our results suggest that the toxicity of Poly(I:C) is higher in Japanese flounder reared at 13°C than in those reared at 17°C.

Key words: VHSV, live vaccine, toxicity, Poly(I:C), Paralichthys olivaceus, Japanese flounder

Protective Efficacy of Formalin-killed Serotype I and II Vaccines for Streptococcus parauberis Infection in Japanese Flounder Paralichthys olivaceus

Kyoko Mori and Yutaka Fukuda*
Fisheries Research Division, Oita Prefectural Agriculture, Forestry and Fisheries Research Center, Oita 879-2602, Japan

(Received May 21, 2012)

ABSTRACT―Japanese flounder Paralichthys olivaceus were immunized intraperitoneally with formalin-killed cells (FKC) prepared from serotype I or II of Streptococcus parauberis. Three weeks after immunization, the fish were challenged with the homologous or heterologous serotype by subcutaneous or intravascular injection. Both serotype FKCs proved to be effective against the challenges with the homologous isolate [relative percent survival (RPS) values: 100%], whereas RPS values in the fish challenged with the heterologous serotype isolates varied from 0% to 100%. These results suggested that each serotype FKC has insufficient cross-protective efficacy against the other serotype.

Key words: Streptococcus parauberis, Paralichthys olivaceus, vaccination, serotype, formalin-killed cell