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NO41 - 2

Oral Immunization of Common Carp with a Liposome Vaccine Containing Aeromonas hydrophila Antigen

<>Shinya Yasumoto1, Tetsuro Yoshimura2 and Teruo Miyazaki1*<>1Faculty of Bioresouces, Mie University, Tsu, Mie 514-8507, Japan
2Faculty of Engineering, Mie University, Tsu, Mie 514-8507, Japan
(Received December 1, 2005)
ABSTRACT邑e developed a liposome vaccine in which Aeromonas hydrophila antigens were entrapped within the liposomal membrane compartment. Oral administration of the vaccine was found to immunize common carp Cyprinus carpio (mean body weight, 30 g) against A. hydrophila. Two fish groups received the liposome vaccine (protein concentration, 33 μg/mL) at doses of 10 and 30 μL/fish/day for a period of 3 days. The levels of antibodies in the serum rose at 2 and 3 wk post vaccination (p.v.) and then declined at 4 wk p.v.. When fish groups orally immunized with a total of 30 μL/fish for 3 days were challenged by an intra-subcutaneous injection with live A. hydrophila at a dose of 3.0 x 105 or 1.0 x 106 CFU/fish at 22 days p.v., the fish were protected against the bacterial infection with RPS of 63.6 or 55.0%, respectively.

Key words: liposome vaccine, oral immunization, Aeromonas hydrophila, Cyprinus carpio

Neobenedenia girellae (Monogenea) Infection of Cultured Cobia Rachycentron canadum in Taiwan

<>Kazuo Ogawa1*, Junko Miyamoto1, Han-ChingWang2, Chu-Fang Lo2 and Guang-Hsiung Kou2<>1Department of Aquatic Bioscience, Graduate School of Agricultural and Life Sciences,
The University of Tokyo, Bunkyo, Tokyo 113-8657, Japan
2Crustacean Virology Laboratory, Institute of Zoology,
National Taiwan University, Taipei, Taiwan,
Republic of China 106
(Received March 6, 2006)
ABSTRACT輸 benedeniid parasite infecting the body surface of cobia Rachycentron canadum cultured in net cages in Taiwan was identified as Neobenedenia girellae. This is the first confirmed case of N. girellae infection of marine fish from Taiwan. N. girellae was not randomly distributed on the host; it concentrated on the dorsal side of the head area (59.7%), especially on the eyes (23.7%), while it was less frequent on the ventral side and not detected on the fins. N. girellae caused considerable histological damage to the host through the attachment by the haptor and possibly through feeding activity by the pharynx. In infected eyes, epithelial cells of the cornea were often partially lost, and the collagenous stroma was considerably thickened and edematous, associated with massive inflammatory cell infiltration.

Key words: Neobenedenia girellae, Rachycentron canadum, pathology, cobia, Taiwan

Serological Characterization of Streptococcus iniae Strains Isolated from Cultured Fish in Japan

<>Kinya Kanai*, Masakazu Notohara, Tatsuo Kato, Kimihiro Shutou and Kazuma Yoshikoshi<>Faculty of Fisheries, Nagasaki University, Nagasaki 852-8521, Japan
(Received March 16, 2006)
ABSTRACT祐treptococcus iniae is known as an important marine and freshwater fish pathogen worldwide. In this paper, we characterized two serological phenotypes in Japanese S. iniae isolates, mainly from Japanese flounder Paralichthys olivaceus. The two phenotypes, designated K+ and K- were distinguished by the presence or absence of capsule. K- cells agglutinated both with anti-K- and K+ type sera, whereas K+ cells agglutinated only with anti-K+ type serum. These two types were indistinguishable by any ordinary biological or biochemical characterization tests. Immunodiffusion test demonstrated the common antigens and a K+ type-specific antigen in the autoclave-extracts of cells. Capsule was observed on the K+ cells, from which acidic polysaccharides were detected. Strains of K+ type were virulent for Japanese flounder, whereas those of K- type were avirulent. There is a direct relationship between the serological phenotypes and the existence of capsule in S. iniae with link to its virulence.

Key words: Streptococcus iniae, serological phenotype, capsule, virulence, Paralichthys olivaceus, Japanese flounder

Detection and Genotyping of Flavobacterium psychrophilum by PCRtargeted to Peptidyl-prolyl cis-trans isomerase C Gene

<>Yasutoshi Yoshiura1*, Takashi Kamaishi2, Chihaya Nakayasu1 and Mitsuru Ototake1<>1Aquatic Animal Health Division, Inland Station, National Research Institute of Aquaculture,
Fisheries Research Agency, Tamaki, Mie 519-0423, Japan
2Aquatic Animal Health Division, National Research Institute of Aquaculture,
Fisheries Research Agency, Minami-Ise, Mie 516-0193, Japan
(Received March 27, 2006)
ABSTRACT 友lavobacterium psychrophilum can be classified into two genotypes, A and B, by the polymorphism in an unexpected product of 290 bp that is amplified with universal primers for gyrase subunit B gene. We identified the 290 bp fragment as a part of coding region of peptidyl-prolyl cis-trans isomerase C (PPIC) gene. Using PCR newly designed for PPIC gene, specific amplification was observed in all F. psychrophilum strains tested, and no amplification occurred in any other bacterial species tested. Moreover, genotype A was found only in isolates from ayu Plecoglossus altivelis.

Key words: Flavobacterium psychrophilum, Plecoglossus altivelis, ayu, peptidyl-prolyl cis-trans isomerase C (PPIC), genotype, coldwater disease

A Possible Mechanism of Quinolone Resistance in Vibrio anguillarum

<>Jun Okuda1*, Shunsuke Kanamaru1, Akihiko Yuasa2, Noriyoshi Nakaoka3, Hidemasa Kawakami3 and Toshihiro Nakai1<>1Graduate School of Biosphere Science, Hiroshima University, Higashi-Hiroshima, 739-8528, Japan
2Fisheries Research Institute, Tokushima Agriculture, Forestry and Fisheries Technology Support Center, Hiwasa, Tokushima 779-2304, Japan
3Ehime Prefectural Fish Disease Control Center,
Uwajima, Ehime 798-0084, Japan

(Received February 13, 2006)

ABSTRACT裕o study a possible quinolone resistance mechanism in Vibrio anguillarum, we examined gyrA and parC mutations among the oxolinic acid-resistant strains and laboratory-derived mutants. One point mutation only in the quinolone resistance-determining region (QRDR) of the gyrA gene was detected in one strain isolated from ayu Plecoglossus altivelis and laboratory-derived mutants with low-level resistance. On the other hand, point mutations in both the gyrA and parC QRDRs were detected in one strain isolated from ayu and a laboratory-derived mutant with high-level resistance. These results suggest that as in other Gram-negative bacteria GyrA and ParC are the primary and secondary targets, respectively, of quinolone in V. anguillarum.

Key words: Vibrio anguillarum, quinolone resistance, gyrA, parC, oxolinic acid

Characteristics and Pathogenicity of Brown Pigment-Producing Vibrio anguillarum Isolated from Japanese Flounder

<>Takamitsu Sakai1*, Hiroo Yamada2, Hiroaki Shimizu2, Kei Yuasa1, Takashi Kamaishi1, Norihisa Oseko1 and Takaji Iida1<>1National Research Institute of Aquaculture, Fisheries Research Agency, Minami-Ise,
Mie 516-0193, Japan
2Fukui Sea-Farming Center, Obama,
Fukui 917-0116, Japan

(Received March 24, 2006)


ABSTRACT輸 Gram-negative rod-shaped bacterium was isolated from diseased Japanese flounder Paralichthys olivaceus (mean total length, 33 mm), during a disease outbreak in a flounder hatchery in Fukui Prefecture, Japan in 2005. The isolated bacterium produced water-soluble brown pigment and was identified as Vibrio anguillarum serotype A (J-O-1) by biochemical and serological tests, and 16S rDNA sequence. The pathogenicity of the isolated bacterium to Japanese flounder was confirmed by intraperitoneal injection, but not by bath immersion. This is the first report of isolation of brown pigment-producing V. anguillarum.

Key words: Vibrio anguillarum, Paralichthys olivaceus, pathogenicity, brown pigment

Outbreaks of Koi Herpesvirus Disease in Rivers of Kanagawa Prefecture

<>Hideo Hara1*, Hideaki Aikawa1, Kazushige Usui2 and Teruyuki Nakanishi3<>1Freshwater Fisheries Experimental Station, Kanagawa Prefectural Fisheries Technology Center, Sagamihara, Kanagawa 229-1135, Japan
2Kanagawa Prefectural Fisheries Technology Center, Miura, Kanagawa 238-0237, Japan
3College of Bioresource Sciences, Nihon University, Fujisawa,
Kanagawa 252-8510, Japan
(Received February 24, 2006)
ABSTRACT柚ass mortality of carp Cyprinus carpio caused by koi herpesvirus disease (KHVD) occurred in seven rivers of Kanagawa Prefecture in 2004. Mortalities of KHVD peaked in May in four of the rivers (early outbreak group) and peaked in June in the other three rivers (late outbreak group). KHVD was first recognized at 15.5 - 8.5゚C in the early outbreak group, and at 18.6・1.2゚C in the late outbreak group. The temperature exceeded 15゚C, which corresponds to the lowest temperature of the viral growth in cell culture.

Key words: koi herpesvirus, KHV, river, water temperature