1. Department of Community Health, Faculty of Public Health, Chalermphrakiat Sakon Nakhon Campus, Kasetsart University, Sakon Nakhon 47000, Thailand
2. Cholangiocarcinoma Research Center, Sakon Nakhon Hospital, Sakon Nakhon 47000, Thailand
3. Department of Parasitology, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand