Mass Mortalities of Goldfish Carassius auratus Infected with Clinostomum Metacercariae, Associated with Elevated Water Temperature

Abstract

Mass mortalities of goldfish Carassius auratus occurred at some farms and wholesalers in Japan, where fish were held at around 33°C to control herpesviral hematopoietic necrosis. All dead fish showed light to moderate Clinostomum infection. Cysts containing metacercariae were accompanied by hemorrhage and congestion, and metacercariae were activated and excysted during the high temperature water treatment. When infected fish were experimentally treated at 20°C, 31°C, 33°C and 35°C, mortality rates reached to 0%, 5%, 40% and 100%, respectively. The experimental results indicated that the elevation of water temperature against the virus infection caused the mass mortalities in Clinostomum-infected goldfish.