SummaryAn integrated epidemiological study of Opisthorchis viverrini consisting of risk factors analysis and parasitation prevalence determination in humans, as well as the assessment the roles of host reservoirs (dogs and cats) and intermediate hosts (cyprinid fi sh) was carried out in the vicinity of Huay Luang dam, Udon Thani province, in the north east of Thailand. The survey was conducted from June 2014 to July 2016 in three sub-districts. Fecal samples were collected from 5,347 participants in 22 villages and the overall prevalence of O. viverrini was found to be 31.5 %. Risk factors for liver fl uke infection were determined from questionnaires analysis which sought demographic data and information about the eating behaviors of the participants. The behavior of raw fi sh consumption correlated signifi cantly with parasitation in the studied areas. The risk factors for O. viverrini infection in humans were associated signifi cantly with age, education, and habitation within a two kilometer range from nearby water and food sources. Questionnaires showed that the drug treatments were not always appropriate. The stools of domestic dogs (n = 468) and cats (n = 262) collected for parasitological analysis and results showed that the zoonotic role of dogs should not be underestimated as has been done previously/in past. The incidence of O. viverrini metacercariae in four cyprinid fi shes Barbonymus gonionotus (n = 124), Cyclocheilichthys repasson (n = 843), Hampala dispar (n = 276) and Henicorhynchus siamensis n = 946), were determined and overall values ranged from 2.4 % to 23.1 %. There was a seasonal variation in metacercariae intensity which ranged from 1 -125 metacercariae per fi sh. The study concluded that transmission ecology should be taken into consideration in developing of control strategies against opisthorchiasis.