魚病研究
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52 巻 , 1 号
選択された号の論文の9件中1~9を表示しています
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総説
  • 西澤 豊彦, 吉水 守
    52 巻 (2017) 1 号 p. 1-5
    公開日: 2017/04/04
    ジャーナル フリー
    Infectious hematopoietic necrosis (IHN) is a disease of salmonid fishes, mainly Oncorhynchus spp., including rainbow trout O. mykiss and Atrantic salmon Salmo salar. IHN causes serious economic losses. It was initially known as endemic in sockeye salmon fry O. nerka and chinook salmon fry O. tschawytscha in West Coast of North America since the 1950s. However, it was spread to Japan, Korea and Taiwan in the 1970s. It was spread to Italy and France in the 1990s. Currently, IHN can be found in many parts of the world, including Russia and South America. Mortality due to IHN in fish with ≤ 0.5 g of body weight can reach 60% to 100%. Mortality caused by IHN will reduces when fish grow bigger. However, the onset of IHN has also increased recently in fish with larger. Here, we describe the molecular epidemiology and virulence changes of IHN virus (IHNV) in Japan, and the detection and identification methods for IHNV. Furthermore, we will discuss the future prospects of IHNV researches.
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  • 良永 知義
    52 巻 (2017) 1 号 p. 6-10
    公開日: 2017/04/04
    ジャーナル フリー
    In the mid-1990s, wild olive flounder showing heavy anemia characterized by deformed erythrocytes with low-stained cytoplasm appeared in Japanese waters. Parasitological, histopathological and hematological studies and surveys revealed that the anemia was caused by the infection with the monogenean Neoheterobothrium hirame on the gill and buccal cavity wall of host. The parasite was later revealed to originally infect southern flounder Paralichthys lethostigma in north America and invade Japanese waters. Bathing in NaCl-supplemented seawater is effective to remove worms from fish. The parasite has been prevailing in wild stocks of olive flounder and may threat the stocks especially in warmer waters.
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  • 山下 浩史, 小田原 和史
    52 巻 (2017) 1 号 p. 11-14
    公開日: 2017/04/04
    ジャーナル フリー
    Since 1996, mass mortalities of cultured Japanese pearl oyster Pinctada fucata martensii have been occurring in western Japan. Mortalities are accompanied with reddish-brown discoloration of the soft body, especially the adductor muscle of oysters. This disease was named “akoya oyster disease (AOD)”. However, the cause of the disease is still unidentified. As a control strategy of this disease, selective breeding of pearl oysters resistant to AOD has been conducted in several public institutes and private groups. The recent decline in outbreaks of AOD can be attributed, in part, to the introduction of selectively bred oysters that are resistant to this disease.
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論文
  • Jun-ichi Hikima, Misaki Morita, Shunsuke Kinoshita, Madhubanti Basu, G ...
    52 巻 (2017) 1 号 p. 15-22
    公開日: 2017/04/04
    ジャーナル フリー
    Tumor necrosis factor alpha (TNF-α)-induced protein 3 (TNFAIP3/A20) is an important deubiquitinating enzyme that takes part in homeostasis of immunity induced by TNF-α. During viral and bacterial infection, it plays a crucial role in negative regulation of innate immune responses in mammals. However, this molecule in fish is still poorly understood. In this study, we identified full-length A20 gene of Japanese pufferfish (Fugu) Takifugu rubripes and performed its expression analyses in various tissues and stimulated cells. Total length of the determined Fugu A20 gene spaned 6,229 bp and consisted of 9 exons and 8 introns. The Fugu A20 gene contained a 2,394 bp open reading frame (ORF) that encoded a 797-amino acid residue. In the exon-intron structure of Fugu A20 gene, the intron-boundary positions in the region having 7 zinc finger (Zf) domains were different from those of human. Expression analysis of Fugu A20 gene exhibited a higher transcription in thymus, head kidney (HK) and spleen tissues than the others. In HK and spleen cells stimulated with LPS, polyI:C and imiquimod, A20 gene was expressed after up-regulation of TNF-α gene expression. These results together suggest that expression of Fugu A20 gene is associated with bacterial and viral infections.
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  • Eitaro Sawayama, Motohiro Takagi
    52 巻 (2017) 1 号 p. 23-30
    公開日: 2017/04/04
    ジャーナル フリー
    In this study, we evaluated the red sea bream iridoviral disease-resistant (RSIVD-resistant) trait of broodstock of red sea bream used in a commercial production based on DNA parentage analysis. We compared family structures of two groups from the same production lot and cultured at two different farms: a population without any outbreak of diseases (farm A) and a high mortality population after an RSIVD outbreak (farm B). The survival percentage of the fish at the farm A and farm B were 86.4% and 20.5%, respectively. Pedigree tracing was conducted on 200 individuals from each farm using eight microsatellite DNA markers among 22 potential breeders (20 dams and 2 sires), and parental pairs at farm A and B were successfully assigned with 93.0 and 90.5%, respectively. After allocating parentage information to each specimen collected from both farms, the estimated survival percentages of each family were calculated. The estimated survival of offspring from a male was 82.3%, and this survival was higher than that from the other male (estimated survival was 2.5%). Also, offspring from a female showed a high survival. These results suggest that some broodstock have resistant traits against RSIVD and shows the potential for developing an RSIVD-resistant strain of red sea bream.
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  • Yih Nin Lee, Kishio Hatai, Osamu Kurata
    52 巻 (2017) 1 号 p. 31-37
    公開日: 2017/04/04
    ジャーナル フリー
    Mass mortality of eggs and larvae of the mud crab Scylla tranquebarica occurred at a hatchery in Sabah, Malaysia in June 2014. The mortality of the larvae reached nearly 100% within 5 days post-hatching. We isolated a pathogenic Peronosporomycetes (Oomycota) from the mud crab eggs and larvae using peptone-yeast-glucose-seawater (PYGS) agar, and then randomly selected the strain IPMB 1402 from the isolates for further study. We observed the formation of fragments inside the hyphae, a characteristic of Haliphthoros species. The strain morphologically most resembled Haliphthoros milfordensis, but comparisons of DNA sequences of the ITS1 region confirmed that the strain was not identical to that species. We classified the strain into a clade with Haliphthoros sp. group 2 (comprising strains NJM 0440, NJM 0449 and NJM 0535) after determining 97-100% intraspecific similarity. Based on distinctive morphological and molecular characteristics, the strain IPMB 1402 is here assigned to the genus Haliphthoros and designated Haliphthoros sabahensis sp. nov. Like other recognized species of Haliphthoros, it is an obligate marine fungus; growth was observed in pH 4-9, and optimum growth temperature was 25-30°C. The strain was experimentally pathogenic to nauplii of the brine shrimp Artemia salina.
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