Fish Pathology
Online ISSN : 1881-7335
Print ISSN : 0388-788X
ISSN-L : 0388-788X
Volume 48 , Issue 3
Showing 1-6 articles out of 6 articles from the selected issue
Research Articles
  • Shinji Tanaka, Shinji Yamamoto, Kazuo Ogawa
    2013 Volume 48 Issue 3 Pages 75-80
    Published: 2013
    Released: September 21, 2013
    The occurrences of Caligus sclerotinosus, a parasitic copepod on cultured red sea bream Pagrus major, were surveyed in fish farms and the phototaxis of adult caligid was experimentally examined. The parasite infection occurred from April to December, in which up to approximately 500 caligids infected the external surface of each diseased fish, covering the whole body surface, eyes and fins. The main disease signs were scale exfoliation, abrasion and ulcerative lesions on the body surface, and chipped fins. Listless swimming near the water surface was also observed. Daily mortalities were usually below 0.1%. When illuminated at different light intensities, most adult caligids showed positive phototaxis and those illuminated at 50 μmol/m2/s swam significantly faster than those illuminated at 200 and 800 μmol/m2/s. When infected fish were illuminated from one direction in a tank, 2.5% of caligids moved from fish to the illuminated wall of tank. When an infected fish and an uninfected fish were separated with a screen partition in each tank and illuminated from one side, 25% of caligids moved from fish in the shaded side to fish in the illuminated side, but never vice versa, showing that fish-to-fish transfer of C. sclerotinosus adults was affected by light conditions.
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  • Takayuki Minami, Masanori Kanemaru, Kazuo Iwata, Masakazu Kuwahara, Ke ...
    2013 Volume 48 Issue 3 Pages 81-87
    Published: 2013
    Released: September 21, 2013
    The virulence of Streptococcus iniae and Lactococcus garvieae strains was evaluated in farmed thread-sail filefish Stephanolepis cirrhifer by intraperitoneally injecting live bacterial cells. These two pathogens were highly pathogenic to thread-sail filefish. The efficacy of each commercial vaccine, namely, S. iniae vaccine, L. garvieae vaccine, and a combined vaccine of S. iniae and L. garviae was evaluated in the fish. The mortality was significantly lowered in both S. iniae- and L. garvieae-vaccinated groups compared to the control group, and both vaccines showed strong protection against the respective pathogens. Moreover, the combined vaccine showed strong protection against these two pathogens. These results suggest that these commercial vaccines are applicable in filefish aquaculture.
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  • Machiko China, Hiroyuki Nakamura, Kaoru Hamakawa, Eishin Tamaki, Satos ...
    2013 Volume 48 Issue 3 Pages 88-96
    Published: 2013
    Released: September 21, 2013
    In 2008, the myxosporean emaciation disease was found in cultured Malabar grouper Epinephelus malabaricus in a fish farm in Okinawa Prefecture, Japan. The disease occurred in winter when water temperature ranged from 21 to 26°C, and the cumulative mortality reached 20-50% among culture tanks. In affected fish, cranial bones were externally apparent due to severe emaciation. The intestinal wall was very thin and the liver exhibited conspicuous green color. Morphological and molecular analyses demonstrated that the causative myxosporean was Enteromyxum leei. Histopathological examinations revealed that the epithelia of the intestine and bile duct of diseased fish were heavily infected with E. leei. The common bile duct was often obstructed by severe inflammation with degenerated tissues and bacteria, suggesting that the abnormal color of the liver was caused by cholestasis. Some diseased fish recovered in a laboratory when water temperature increased naturally to 27-30°C in summer months, and the parasite was not detected in those fish. Experimental transmission of E. leei to naïve Malabar grouper was successfully achieved by cohabitation with infected grouper or by feeding with the feces of infected fish. This is a new host and locality record for E. leei.
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