[Prevalence of metacercariae of Clonorchis sinensis in wild freshwater fishes from Nenjiang River around Qiqihaer City]

From May to November 2013, a total of 1175 wild freshwater fishes were collected from the rivers of Chuoer, Yalu, Wuyuer, Alun, and Yin in Nenjiang River basin Qiqihaer City, and examined for metacercariae by direct compression method. The metacercariae were collected by artificial digestion method. Forty Kunming mice were infected with 30-40 metacercariae of Clonorchis sinensis. The mice were sacrificed 36 days after infection, and the adult worms were collected from bile duct, and observed under microscope. The results showed that a total of 1 175 fishes, belonging to nine species were taken from the Nenjiang basin of Qiqihaer region. The infection rate of Clonorchis sinensis metacercariae was 51.2% (602/1 175). All the species were infected besides Silurus asotus, and the highest prevalence (82.7%, 91/149) was found in Longnose gudgeon and the lowest (7.1%, 6/84) in Perccottus glenii. Among the rivers, the highest prevalence of metacercariae was in Wuyuer River. (65.7%, 218/332), and the lowest was in Alun River and Yin River (24.1%, 67/278) (P0.05). Each part of the body in the Carassius auratus and Pseudorasbora parva were susceptible for metacercariae. The main infection site in Longnose gudgeon was the fish scales, and C. sinensis metacercaria was first discovered in the brain tissue of Phoxinus lagowskii. The experimental results showed that the adult worms of C. sinensis were found in the hepatic bile duct of the mice, with an infection rate of 85.0% (34/40). The suckers, digestive system and reproductive system of C. sinensis were visible clearly.