Abstract

An outbreak of infectious disease in 30,000 marble gobies (Bleeker, Oxyeleotris marmoratus) cultured at a density of 5,000 to 8,000 fish per pond at a fish farm in the central Taiwan was reported to the Nantou County Animal Disease Center and the Central Taiwan Aquatic Disease Center. The mortality rate was approximately 40% (12,000/30,000). In May 2010, clinical signs of sluggish behavior, atypical swimming behavior at the edge of the pond and sudden death were noted among the marble gobies, which ranged from fry (12.7 cm) to juveniles (550 g). Moribund juveniles fish (n=5) were taken for diagnosis. Gross examination demonstrated cutaneous melanosis, local ulcers, and fatty liver. Gill imprint examined under light microscope revealed eggs of Dactylogyruscrucifer. Histopathology examination revealed inclusion body-like structures, necrosis, and hypertrophy in the pillar cells of gill, and multifocal proliferation of filament cells in gills. Additionally, lymphoid depletion, macrophages hyperplasia, and hypertrophy with the presence of intracytoplasmic vacuoles in the spleen as well as decreased numbers of melanomacrophages centers and hemocytoblasts in the kidney were observed. The result of polymerase chain reaction (PCR) of our case pathogen yielded a 570 bp fragment, which was consistent with the products of PCR obtained from red sea bream iridovirus (RSIV). The final diagnosis was RSIV infection in marble gobies. Additionally, antimicrobial agent sensitivity test showed no remarkable findings.

Key words: Fish, marble goby, red sea bream iridovirus, Taiwan