Epidemiology of Metagonimus yokogawai metacercariae infection in fresh water fishes of Kanagawa and Shizuoka Prefectures

摘要

M. yokogawai infection was diagnosed in ayu from Sakawa, Haya and Fujiki rivers in Kanagawa Prefecture between 1995 and 1997. The infection rate was 73.7 to 87.1%. The numbers of metacercariae per infected ayu were 12 to 348. Leuciscus hakonensis from Haya and Sakawa rivers were severely infected (87.0 to 100%), and the number of metacercariae per infected fish was 27 to 1247. No infection was diagnosed in rainbow trout from Haya and Fujiki rivers. Five fish species from Kano and Raikou rivers in Shizuoka Prefecture were infected. Infection rate was 80% in ayu (number of parasites 25 to 428), 93.8 to 100% in L. hakonensis (36 to 1257 parasites per fish), 46.6 to 56.7% in Zacco platypus (16 to 269 parasites per fish), 76.3% in Z. temmincki (24 to 198 parasites per fish) and 100% in Phoxinus oxycephalus (49 to 165 parasites per fish). No infection was observed in rainbow trout, bull trout, O. masou macrostomus and Hemibarbus labeo barbus. Three of 212 ayu (1.4%) cultivated in well water were infected, while 142 of 223 fishes cultivated in river water (63.7%) were infected. The infection rate and number of metacercariae per infected fish increased in late autumn. No infection was seen in cultivated rainbow trout, amago and bull trout.