[en] The purpose of the present study is to observe the survival and development of Clonorchis sinensis metacercariae in their final hosts after ⁶⁰Co gamma irradiation of isolated metacercariae or in fish. Guinea pigs or albino rats were orally infected with metacercariae by gavage. Bioassay, faecal examination for ova and dissection of infected animals were the methods used for the estimation of minimal effective dose (MED) of gamma irradiation to control infectivity of C. sinensis metacercariae. Results showed that the MED for isolated metacercariae was 0.05 kGy. The LD₅₀ of the irradiation dose for metacercariae in fish was 0.05 kGy, and the MED was 0.15 kGy. No significant difference in radiation susceptibility to ⁶⁰Co gamma irradiation was found among C. sinensis metacercariae in fishes collected at different localities in northern, central or southern parts of China. The present finding suggests that irradiation of fish by 0.15 kGy could control infectivity of C. sinensis metacercariae and thus be adopted as a control measure in preventing infections. (author). 10 refs, 4 tabs

[en] Using ⁶⁰Co as source of radiation, a study was made to observe the effect of irradiation on the viability of Paragonimus westermani metacercariae in Potamon sp. crabs. The crabs were collected in mountain regions in Zheijiang Province of China endemic for paragonimiasis. Adult cats and albino mice were infected with the metacercariae irradiated at different doses. Dissection of the animals was conducted 90 or 30 days, respectively, after infection for recovery of the lung fluke from infected cats, and antimetacercaria antibody was tested with sera from infected mice by enzyme linked immunosorbent assay (ELISA). Results showed that metacercariae were unable to grow into adult worms in cats after exposure to gamma irradiation at a dose of 0.10 kGy. However, a small number of metacercariae exposed to a dose of 2.0 kGy was still able to encyst and survive for 30 days. No young or adult worms were recovered from mice when the metacercariae were irradiated at a dose of 2.5 kGy. Seropositive results by ELISA were obtained when the mice were infected with metacercariae irradiated at doses ranging from 2.0-3.5 kGy. The susceptibility of P. westermani metacercariae to irradiation is discussed. (author). 4 refs, 2 tabs