Fish Pathology
Online ISSN : 1881-7335
Print ISSN : 0388-788X
ISSN-L : 0388-788X
Volume 51 , Issue 2
Showing 1-9 articles out of 9 articles from the selected issue
  • Kazuo Ogawa
    2016 Volume 51 Issue 2 Pages 39-43
    Published: 2016
    Released: July 08, 2016
    Heterobothrium okamotoi infects the gills and branchial cavity wall of Japanese pufferfish Takifugu rubripes, feeding on blood from the gills. Infection of this monogenean can cause anemia, and adult worms on the branchial cavity wall induce inflammation and tissue necrosis by the action of haptoral clamps. Eggs deposited as a long string easily entangle on the culture net, which is prone to heavy infection of pufferfish cultured in net cages, as the oncomiracidium, hatched larva, can encounter the host fish at much higher chances than expected in natural waters. Prevention of infection is practically impossible as its life cycle has been established in culture farms. Chemotherapy with hydrogen peroxide or febantel, a benzimidazol, is effective but repeated treatment may be required, as immunity acquired by infected fish is not perfect. Biological data on H. okamotoi should be effectively incorporated in its control measures.
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  • Terutoyo Yoshida
    2016 Volume 51 Issue 2 Pages 44-48
    Published: 2016
    Released: July 08, 2016
    Streptococcosis caused by the genera Streptococcus and Lactococcus have occurred in cultured freshwater, brackish water and marine fish species owing to the worldwide development of intensive aquaculture. In Japan, four pathogens, Streptococcus iniae, S. parauberis, S. dysgalactiae and Lactococcus garvieae, have been observed in aquaculture. Infections of these pathogens cause high mortality rates in the species important for aquaculture such as yellowtail, red sea bream and flounder. Recently, commercial vaccines have been licensed against these pathogens to prevent the infections in some aquaculture species. This review describes the outlines and topics of the diseases.
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  • Mamoru Yoshimizu
    2016 Volume 51 Issue 2 Pages 49-53
    Published: 2016
    Released: July 08, 2016
    The first outbreak of bacterial kidney disease (BKD) of salmonids occurred in the autumn of 1973 in Hokkaido, Japan. Subsequently, outbreaks of BKD were confirmed in Hokkaido and main land of Japan. Most of the cases were caused by imported eyed eggs of coho salmon Oncorhynchus kisutch. In this review, pathogenicity of the causative agent R. salmoninarum (Rs), culture methods of Rs, serological and Rs specific gene detection methods for diagnoses, disease signs of infected fish, and distribution of BKD in Japan are described. Also, preventive measures of vertical transmission and control methods of BKD are introduced.
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Research Article
  • Toyohiro Nishioka, Takashi Kamaishi, Jun Kurita, Tohru Mekata, Ikunari ...
    2016 Volume 51 Issue 2 Pages 54-59
    Published: 2016
    Released: July 08, 2016
    Candidatus Xenohaliotis californiensis, a Rickettsia-like organism (RLO) that causes ‘withering syndrome’ (WS) in abalone, has been recently detected in Japan. We analyzed partial nucleotide sequence (113 bp) of 16S rRNA of WS-RLOs (n = 335) from Japanese black abalone Haliotis discus discus, Ezo abalone H. discus hannai, giant abalone H. gigantea, tokobushi abalone H. diversicolor aquatilis and fukutokobushi abalone H. diversicolor diversicolor. All the sequences from Japanese black, Ezo and giant abalone were identical, but different from those from tokobushi and fukutokobushi at one nucleotide position. We also conducted cohabitation challenge to determine whether the WS-RLO in fukutokobushi infects Japanese black and giant abalone or the agent in Japanese black abalone infects fukutokobushi. Twenty fukutokobushi naturally infected with WS-RLO were cohabited with 10 healthy individuals of each of Japanese black, giant, and fukutokobushi abalone for a total of 84 days. At the end of the experiment, surviving fukutokobushi abalone were positive in PCR test for WS-RLO, but negative for that of Japanese black and Ezo abalone. In the reverse combination experiment, in which naturally infected Japanese black abalone were cohabited with these three species, WS-RLO transmissions were found in Japanese black and Ezo, but not in fukutokobushi abalone. These results suggest that two genetic variants of WS-RLO have a different host specificity.
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Short Communications