Fundamental study on fungal diseases of fish and shellfish

1992 Fiscal Year Final Research Report Summary

• Project/Area Number: 03660328
• Research Category: Grant-in-Aid for General Scientific Research (C)
• Allocation Type: Single-year Grants
• Research Field: Applied veterinary science
• Research Institution: Nippon Veterinary and Animal Science University
• Principal Investigator: HATAI Kishio Nippon Veterinary and Animal Science University, Faculty of Veterinary and Animal Science, Professor, 獣医畜産学部, 教授 (30164841)
• Project Period (FY): 1991 – 1992
• Keywords: striped jack / Scytalidium sp / Ochroconis humicola / histopathology / systemic mycosis / Optimal temperature / protease / MIC

Research Abstract

Scytalidium infection was found in striped jack (Pseudocaranx dentex) with systemic mycosis. Ochroconis humicola was also isolated from the lesions. The external clinical signs were blackish patches and ulcers formed on the surface, especially at the base of the dorsal fin, at the tip of the snout, and the anal area. Inoculation experiments on striped jack revealed that these fungi were the causal agent of the mycosis. However, the pathogenicity of the Scytalidium sp. appeared stronger than that of the O. humicola from the histopathological findings. Optimal temperature of S. sp. K2 was 24ﾟC, but no growth showed at under 8ﾟC and over 35ﾟC. From the results, the fungus was thought to be safe to humans. Histopathologically, necrosis and fusion of muscle fibers were observed in the muscles of fish used for artificial infection tests. This shows protease from the fungi is produced in the muscle. It was thought that the protease was a very important enzyme to make the lesions. The effects of some drugs on the Scytalidium sp. K2 were tested in vitro, but no effective drugs were found.