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Diseases of Aquatic Organisms

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DAO 59:1-9 (2004)  -  doi:10.3354/dao059001

Susceptibility of juvenile humpback grouper Cromileptes altivelis to grouper sleepy disease iridovirus (GSDIV)

Ketut Mahardika1, Zafran1, Asami Yamamoto2, Teruo Miyazaki2,*

1Gondol Research Institute for Mariculture, PO Box 140, Singaraja, Bali, Indonesia
2Faculty of Bioresources, Mie University, 1515 Kamihama, Tsu, Mie 514-8507, Japan
*Corresponding author. Email:

ABSTRACT: Susceptibility of juvenile humpback grouper Cromileptes altivelis to the grouper sleepy disease iridovirus (GSDIV) was examined. GSDIV-containing inocula for challenge were obtained using a filtrate of spleen tissues from donor fish (orange-spotted grouper Epinephelus coioides) infected with GSDIV. Groups injected with the primary filtrate showed lower mortalities (30 to 60%) than groups receiving the 10-4 diluted inoculum (90 to 100% mortality). This result was contrary to the expectation that fish challenged with a higher concentration of virus would show higher mortality. Electron microscopy revealed that moribund fish receiving the 10-4 diluted inoculum displayed massive formation of typical inclusion body-bearing cells (IBCs) containing an intracytoplasmic inclusion body with many virions in the 180-200 nm size range propagated within a virus assembly site. In contrast, survivors in fish receiving the primary filtrate showed the formation of unusual IBCs containing an abnormal inclusion body that was characterized by the assembly of a small number of deformed virions. This impaired virus assembly appeared to prevent mortality in the challenged fish and was assumed to be due to an interferon-like effect of a previously unknown substance that was passed on to the challenged fish with the tissue filtrate from the donor fish.

KEY WORDS: Humpback grouper · Cromileptes altivelis · Grouper sleepy disease iridovirus · Tropical iridovirus · Inclusion body-bearing cells · Interferon-like effect

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