1. Department of Microbiology, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand
2. World Health Organization Collaborating Centre for Research and Control of Opisthorchiasis, Tropical Disease Research Center, Faculty of Medicine, Khon Kaen University, Khon Kaen 40002, Thailand
3. Institute of Infection, Veterinary and Ecological Sciences, University of Liverpool, Liverpool L69 7ZX, United Kingdom