title: The importance of wild fish in the epidemiology of Clonorchis sinensis in Vietnam.
abstract: 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.
authors.affiliation: Research Institute for Aquaculture No1, Dinh Bang, Tu Son, Bac Ninh, Vietnam.
authors.forename: Thanh Ngoc
authors.initials: TN
authors.lastname: Bui
authors.affiliation: Research Institute for Aquaculture No1, Dinh Bang, Tu Son, Bac Ninh, Vietnam.
authors.forename: Thanh Thi
authors.initials: TT
authors.lastname: Pham
authors.affiliation: Research Institute for Aquaculture No1, Dinh Bang, Tu Son, Bac Ninh, Vietnam.
authors.forename: Nguyen Thi
authors.initials: NT
authors.lastname: Nguyen
authors.affiliation: Institute of Ecology and Biological Resources, Vietnam Academy of Science and Technology, 18 Hoang Quoc Viet, Nghia Do, Cau Giay, Hanoi, Vietnam.
authors.forename: Ha Van
authors.initials: HV
authors.lastname: Nguyen
authors.affiliation: Department of Preventive Medicine and Biometrics, School of Medicine, Uniformed Services University of the Health Sciences, Bethesda, MD, USA.
authors.forename: Darwin
authors.initials: D
authors.lastname: Murrell
authors.affiliation: Research Institute for Aquaculture No1, Dinh Bang, Tu Son, Bac Ninh, Vietnam. phanthivan_vn@yahoo.com.
authors.forename: Van Thi
authors.initials: VT
authors.lastname: Phan
mesh_terms: D000818:Animals; D000835:Animals, Wild / Q000145:classification / Q000469:parasitology; D003003:Clonorchiasis / Q000469:parasitology / Q000662:veterinary*; D003004:Clonorchis sinensis / Q000145:classification / Q000235:genetics / Q000254:growth & development / Q000302:isolation & purification*; D005393:Fish Diseases / Q000469:parasitology*; D005399:Fishes / Q000145:classification / Q000469:parasitology; D058488:Metacercariae / Q000145:classification / Q000235:genetics / Q000254:growth & development; D012908:Snails / Q000469:parasitology; D014744:Vietnam / Q000453:epidemiology
keywords: Clonorchis sinensis; Epidemiological study; Fish hosts; Liver flukes; North Vietnam; Reservoir