JAPANESE
HOME > Volume and Number > NO36 - 2

NO36 - 2

Infection of the Digenean Aerobiotrema muraenesocis in the Swim Bladder Lumen of Pike Eel Muraenesox cinereus

December 25, 2000<>Yoshiaki Yamada1*, Hideo P. Oka1, Akihiro Okamura1, Satoru Tanaka1, Tomoko Utoh1, Noriyuki Horie1, Naomi Mikawa1 and Kazuo Ogawa2<>1 IRAGO Institute, 377 Ehima-Shinden, Atsumi, Aichi 441-3605, Japan
2 Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi 1-1-1, Bunkyo, Tokyo 113-8657, Japan

ABSTRACT猶ike eels Muraenesox cinereus (41・16 cm in total length; n=23) purchased from fish markets in Aichi Prefecture were infected with the digenetic trematode Aerobiotrema muraenesocis in the swim bladder (11 out of 23 fish; intensity of infection 1・7). Effects of the infection on the host were studied and partial life history of this trematode was postulated. Eggs of the trematode were spherical or sub-spherical. They could hatch in the water with a wide range of salinity (1/3 to undiluted). Hatched larvae had an unusual appearance, with long cilia limited on the antero-lateral sides of their body. Histochemical staining revealed that the trematode sucks blood from the swim bladder of the host. Moreover, severe histopathological changes were observed in the tunica interna of the swim bladder, including deep and irregular undulations of the epithelium, marked thickening of the tunica propria and hemorrhaging ulcers within the tunica interna. In case where these pathological changes had proceeded, the intimate association of the epithelium with the capillaries in the tunica propria was severely disturbed. According to these histopathological observations, it appears that heavy infection with this trematode may cause lowered functions of the host痴 swim bladder.

Pathogenicity of the Epizootic Ulcerative Syndrome (EUS)-Associated Rhabdovirus to Snakehead Ophicephalus striatus

December 27, 2000<>Gilda D. Lio-Po1*, Lawrence J. Albright2, Garth S. Traxler3 and Eduardo M. Lea1<>1 Aquaculture Department, Southeast Asian Fisheries Development Center, Tigbauan, Iloilo 5021, Philippines
2 Department of Biological Sciences, Simon Fraser University, Burnaby, B.C. V5A 1S6, Canada
3 Pacific Biological Station, Nanaimo, B. C. V9R 5K6, Canada

ABSTRACT裕he rhabdoviruses isolated from EUS-affected snakeheads in the Philippines was tested for pathogenicity to healthy, naive snakehead Ophicephalus striatus fry, fingerlings and juveniles. Virus exposure of naive snakehead fry and fingerlings by bath at 20・2.5℃ resulted in significant mortalities (p<0.01) with no apparent lesions. Naive snakehead juveniles when injected intramuscularly (IM) with the EUS-associated rhabdovirus at ambient water temperature (28・2℃) did not develop any lesion. However, similarly treated snakehead juveniles at 20・2.5℃ developed dermal lesions 3・ days following treatment. The lesions progressed from slight to moderately advanced lesions by days 10・2 but not to deep ulcers as exhibited by naturally EUS-affected snakeheads. Mean mortalities were higher in the virus-injected fish (72%) compared to those in controls (33%). Moreover, the virus was reisolated from fish in the 20・2.5℃ treatment but not from fish in the 28・2℃ treatment. Virus from infected tissue filtrate and the virus passaged 3 or 4 times induced similar dermal lesions if the rhabdovirus concentration was 103 TCID50/fish or higher. When administered orally, by bath, by intraperitoneal (IP), IM and subdermal injections to snakehead juveniles, only the latter two viral routes induced dermal lesions. However, IP injection of the rhabdovirus caused 75% mortalities but none in control fish. The results demonstrate the pathogenicity of the rhabdovirus isolates to naive snakeheads at low (20・2.5℃) rearing water temperatures.

The protective effect of recombinant glycoprotein vaccine against HIRRV Infection

January 14, 2001<>Joung-Im Eou1, Myung-Joo Oh2, Sung-Ju Jung2 , Young-Hwan Song1 and Tae-Jin Choi1*<>1 Department of Microbiology, Pukyong National University, Pusan, 608-737, Korea,
2 Department of Fish Pathology, Yosu National University, Yosu, 550-749, Korea

ABSTRACT幽irame rhabdovirus (HIRRV) was first reported from flounder (Paralichthys olivaceus) in Japan, and has recently been isolated from an aquaculture farm in the Tongyoung area of Korea. Total RNA isolated from RTG-2 cells infected with HIRRV was used in RT-PCR to obtain a cDNA coding for the glycoprotein of HIRRV Korean strain, CA-9703. Around half sized G protein in the C-terminal region was expressed as glutathione-S-transferase fusion protein, and used as viral vaccine against HIRRV. Flounder fry were vaccinated with low (50 mg/mL) and high (300 mg/mL) doses of vaccine by immersing them for 7 min in vaccine solution. After 1 month, the fish were challenged with HIRRV either by immersion or intraperitoneal injection. Specific losses of fish treated with low and high vaccine doses by intraperitoneal injection challenge were both 6.7%, in contrast to 43.3% in non-vaccinated fish. Losses of vaccinated fish by immersion challenge were 1.7% and 0% for low and high vaccine doses, respectively, and 15% for the non-vaccinated control.

In Vitro Inhibition of Saprolegnia by Bacteria Isolated from Lesions of Salmonids with Saprolegniasis

January 24, 2001<>Mortada M. A. Hussein1,2 and K. Hatai1*<>1 Division of Fish Diseases, Nippon Veterinary and Animal Science University, Tokyo 180-8602, Japan
2 Department of Fish Diseases and Management, Faculty of Veterinary Medicine, Cairo University, Beni-Suef Branch, Beni-Suef 62111, Egypt

ABSTRACT輸 study was conducted to investigate the antifungal activity of some bacteria isolated from the lesions of salmonid fishes with saprolegniasis. Five of 47 isolates inhibited the growth of Saprolegnia parasitica H2 and S. salmonis NJM 9851 on solid media. Among 8 media examined, BHI, HI, and to a lesser extent NA were suitable for demonstrating the antifungal activity. The inhibitory activity against the tested Saprolegnia did not reside in supernatant of bacterial broth culture of the selected strains. The strains which produce antifungal substances belong to the genera Alteromonas, Pseudomonas, and Aeromonas. These results suggest that the selected bacteria are natural competitors of Saprolegia, and may be used for biocontrol of Saprolegnia in aquaculture.

Prevention of Lagenidiales Infections in Artemia salina Larvae by High pH of Rearing Water

February 8, 2001<>Hideki Yasunobu<>Hyogo Prefectural Fisheries Experimental Station Minami-Futami 22-2, Akashi, Hyogo 674-0093, Japan

ABSTRACT裕he effect of high pH (pH 9.25) of rearing water on the prevention of infection of the brine shrimp Artemia salina larvae with four fungal species of Lagenidiales was examined. The four fungi, all pathogenic to crustaceans, were Halocrusticida parasitica isolated from greasyback shrimp Metapenaeus ensis, Haliphthoros sp. and Haliphthoros milfordensis isolated from swimming crab Portunus trituberculatus and Lagenidium callinectes isolated from mud crab Scylla serrata. The in vitro growth of Halocrusticida parasitica was reduced at pH 9.25 and no infection was observed in the brine shrimp exposed to zoospores in the sea water at pH 9.25. The in vitro growth of Haliphthoros sp. and Haliphthoros milfordensis was reduced at pH 9.25 and infection rates at pH 9.25 were about half of the rate at pH 8. The growth of L. callinectes was not arrested at pH 9.25 and the infection rate at pH 9.25 was 100%. These results indicate that the pH adjustment of rearing water to 9.25 can be used to prevent infections with Halocrusticida parasitica and the two species of Haliphthoros in swimming crab larvae, but not for the infection with L. callinectes.

Seasonal Fluctuations in the Occurrence of Abnormal Enlargement of the Ovary of Pacific Oyster Crassostrea gigas at Gokasho Bay, Mie, Japan

February 28, 2001<>Sonomi Imanaka1, Naoki Itoh2, Kazuo Ogawa2* and Hisatsugu Wakabayashi2<>1 Laboratory of Aquatulture, Department of Aquatic Bioscience, Graduate School of Agicultural and Life Sciences, The University of Tokyo, Maisaka, Hamana-gun, Shizuoka 431-0211, Japan
2 Laboratory of Fish Diseases, Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences, The University of Tokyo, Yayoi, Bunkyo, Tokyo 113-8657, Japan

ABSTRACT祐easonal occurrences of the abnormally enlarged ovary of Pacific oysters Crassostrea gigas caused by an unidentified intracellular protozoan parasite was investigated in Gokasho Bay, Mie Prefecture, Japan. Cultured and wild oysters were collected bimonthly for one year from July 1996, and seasonal fluctuations in the prevalence of infection, parasite development and histological changes of the infected tissue were examined. Parasites, very similar to Marteilioides chungmuensis infecting Pacific oysters in Korea, had 8 forms, 4 of which were frequently observed, while the other 4 forms, which were not described in M. chungmuensis, were rare. The total prevalence of infection (percentage of infected oysters positive for at least one of the two examinations: gross and smear inspections of the ovary) was usually higher than the gross prevalence of infection, indicating that infected oysters included ones without visible legions. In cultured oysters, the prevalence of infection increased in summer, suggesting that active multiplication of the parasite takes place in warm water months. From autumn through spring, no substantial change in the total prevalence of infection was observed in cultured oysters (18・0%), while it continued to decline in wild oysters during that period. These differences between cultured and wild oysters could be attributed to the oyster size and environmental factors such as salinity. Histologically, the number of infected oocytes increased in summer, but decreased in winter. From the variations in the parasite morphology and maturation of oocytes, the life cycle of the parasite and the mechanism of the legion formation are postulated.

Detection of White Spot Syndrome Virus (WSSV) in Wild Captured Shrimp and in Non-cultured Crustaceans from Shrimp Ponds in Bangladesh by Polymerase Chain Reaction

October 30, 2000<>Md. Shahadat Hossain, S. K. Otta, Indrani Karunasagar and Iddya Karunasagar*<>Department of Fishery Microbiology, College of Fisheries, Mangalore ・575 002, India

ABSTRACT裕he presence of white spot syndrome virus (WSSV) in wild Penaeus monodon, other wild shrimps, and in non-cultured crustaceans from shrimp ponds/ghers in Bangladesh was studied by polymerase chain reaction (PCR). Wild shrimps viz. P. mondon, P. semisulcatus, P. indicus, Metapenaeus monoceros, M. brevicornis and Palaemon styliferus were positive for WSSV. The non-cultured shrimps M. monoceros, M. brevicornis, freshwater prawn Macrobrachium rosenbergii, crabs Scylla serrata and Pseudograpsus intermedius from shrimp ponds/ghers were WSSV positive. This is the first study on the detection of WSSV in Bangladesh by PCR and first report of P. styliferus, M. monoceros, M. brevicornis and P. intermedius as WSSV carriers.

A Rapid and Simple Assay to Determine the Proliferation of Larval and Juvehile Fish Splenocytes

November 30, 2000<>Motoaki Yagi1・Kouichi Hatasaki2・Noboru Nakahara2・Kenji Hara3・Katsuyasu Tachibana1* and Mutsuyosi Tsuchimoto1<>1 Laboratory of Fishery Nutritional Science, Graduate School of Marine Science and Engineering, Nagasaki University, Bunkyo-machi 1-14, Nagasaki 852-8521, Japan
2 Laboratory of Fishery Nutritional Science, Faculty of Fisheries, Nagasaki University, Bunkyo-machi 1-14, Nagasaki 852-8521, Japan
3 Laboratory of Marin Biochemistry, Graduate School of Marine Science and Engineering, Nagasaki University, Bunkyo-machi 1-14, Nagasaki 852-8521, Japan

ABSTRACT輸 simple assay to determine the proliferation of larval and juvehile fish splenocytes using Alamar Blue (AB) was studied. Splenocytes were separated by Percoll gradient from Japanese flounder Paralichthys olivaceus (1-year-old), then the proliferation of splenocytes stimulated by mitogen (concanavalin A: ConA, pokeweed mitogen: PWM, or lipopolysaccharide: LPS) was detected using AB. The relationship between number of splenocytes and specific absorbance exhibited a positive significant correlation. The optimum condition of this assay was 5 ※ 105cells/well of splenocytes with mitogens (ConA 100 mg/mL, PWM 10 mg/mL or LPS 1 mg/mL) for 72 h. Proliferation of each splenocyte from juveniles of Japanese flounder and larvae of Japanese parrotfish Ophegnathus fasciatus and tiger puffer Takifugu rubripes was detectable by this assay.

Pathogenicity of Marine Birnavirus against Ayu Plecoglossus altivelis

January 24, 2001<>Sung-Ju Jung1*, Satoru Suzuki2, Myung-Joo Oh1 and Kenji Kawai3<>1 Department of Fish Pathology, Yosu University, Yosu 550-749, Korea
2 Center for Marine Environmental Studies, Ehime University, Matsuyama 790-8577, Japan
3 Department of Aquaculture, Kochi University, Nankoku, Kochi 783-8502, Japan

ABSTRACT猶athogenicity of a marine birnavirus (AY-98) isolated from diseased ayu Plecoglossus altivelis was investigated. Cumulative mortalities in the intraperitoneally injected groups of ayu in two weeks were 70% (dose 105.4 TCID50/fish)・1%(105.8 TCID50/fish) in duplicated experiments. Histologically, the naturally and experimentally infected fish showed brain congestion and pancreatic necrosis. From the symptoms of body deformity and congestion in the brain, it was thought that
AY-98 is similar to viral deformity virus, the birnavirus isolated from yellow tail Seriala quinqueradiata with deformity.

Symposium 「Crrent Status of Fish Vaccine Development in Japan」

March 29, 2001<>N. Okamoto1, T. Nakanishi2 and T. Iida3<>1 Department of Aquatic Biosciences, Tokyo University of Fisheries, Konan 4, Minato-ku, Tokyo 108-8477, Japan
2 Department of Veterinary Medicine, Nihon University, 1866 Kameino, Fujisawa, Kanagawa 252-8510, Japan
3 Department of Biological Production and Environmental Science, Faculty of Agriculture, Miyazaki University, Gakuen Kibanadai-Nishi 1, Miyazaki 889-2192, Japan

ABSTRACT輸 symposium entitled 鼎rrent status of fish vaccine development in Japan・as held by the Japanese Society of Fish Pathology in Tokyo on 29th March, 2001. This was aimed to have an overview of the status quo of fish vaccine developments in Japan, especially those for marine fishes. In Japan, a vibrio vaccine to ayu Plecoglossus altivelis was first developed in 1988 and five vaccines have been totally developed until now. In this symposium, ten subjects were included in five categories: (1) Vaccine-use system, utilization and practical problems, (2) Vaccines developed or being developed, (3) Genetic engineering techniques and adjuvants for vaccines (4) General control methods to prevent fish diseases, and (5) Problems confronting the development of fish vaccines in Japan. Vaccines will contribute to make safe products in aquaculture, which can give 菟ace of mind・to consumers. Vaccines developed in Japan have been effective to protect fish from the target diseases and it was emphasized that fish condition should be kept healthy to get a good result by vaccination.