Preliminary findings of a high prevalence of Clonorchis sinensis in wild-caught fish in a North Vietnam reservoir (Thac Ba reservoir, Yen Bai Province) prompted a longitudinal epidemiological study of fish infections. Monthly collections of fish from September 2014 to August 2015 were processed for recovery of metacercariae; 1219 fish, representing 22 species, were examined. Seven species were infected with C. sinensis metacercariae. Four species, Toxabramis houdemeri, Hemiculter leucisculus, Cultrichthys erythropterus, and Culter recurvirostris, had high prevalence (31.1 to 76.7 %); metacercarial intensities ranged from 3.9 to 65.7 metacercariae/fish. A seasonal variation of C. sinensis prevalence was observed in T. houdemeri. Variation in intensity of infection occurred in C. erythropterus and H. leucisculus. Intensity and prevalence of C. sinensis in the most highly infected species, T. houdemeri, varied by fish size; prevalence was higher in fish weighing more than 3 g, and intensity was higher in fish weighing more than 5 g. The distribution of metacercariae in the body region of T. houdemeri was significantly higher in the caudal fin (14.7 metacercariae/g), compared to the body and head regions (0.7 and 1.4 metacercariae/g, respectively). Further epidemiological investigations on C. sinensis in this reservoir region should include assessing the relative risk of the different fish species for humans based on the latter's food preferences, and the prevalence of C. sinensis in the community. The snail intermediate host(s) in the reservoir should also be identified along with the ecological factors influencing its exposure to C. sinensis eggs and its subsequent transmission of cercariae to fish. Also needed are investigations on the relative importance of wild and domestic reservoir hosts as sources of egg contamination of the reservoir.

The antibacterial activity of herbal extracts to Vibrio parahaemolyticus causing acute hepatopancreatic necrosis disease in whiteleg shrimp (Litopenaeus vannamei) was studied and carried out in the School of Agriculture and Aquaculture, Tra Vinh University. The results showed that the inhibition zone of Muntingia calaburaleaf extract with ethanol 70% was 18.00 ± 0.00mm, Muntingia calabura leaf extract with ethanol 90% was 17.33 ± 0.58 mm and Muntingia calabura fresh leaf extract was 13.00 ± 0.00 mm. Minimum inhibitory concentration (MIC) of Muntingia calabura leaf extract with ethanol 70% and 90% were 5.120 mg/L, 10.240 mg/L. MIC value of Al lium cepa extract with ethanol 70% and 90% were 40.960 mg/L, Physalis angulata extract with ethanol 70% and 90% were 81.920 mg/L. The results showed that the antimicrobial activity was highest in the Muntingiacalabura leaf extract and lowest in Physalis angulata extract.