Asian Pacific Journal of Cancer Prevention, Vol 13, 2012 1235 DOI:http://dx.doi.org/10.7314/APJCP.2012.13.4.1235 Opisthorchis viverrini Metacercariae of Carcinogenic Human Liver Fluke in Nakhon Ratchasima, Thailand Asian Pacific J Cancer Prev, 13, 1235-1240 Introduction Opisthorchis viverrini, fish-borne trematode infection causes a serious public-health problem in Southeast Asia mainly Thailand, Cambodia, and Laos PDR. In Thailand, opisthorchiasis is a major public health problem in the Northeastern and Northern region, and it is estimated that 5.5 million people are infected with the causative parasite (Sripa et al., 2010). Human have been infected by ingesting undercooked fish containing infective metacercariae, this is very common in the northeastern and northern region particularly in rural areas (Sadun, 1955; Sithithaworn et al., 1997; Jongsuksuntigul & Imsomboon, 2003). The infection is associated with a number of hepatobiliary diseases, including cholangitis, obstructive jaundice, hepatomegaly, cholecystitis and cholelithiasis (Harinasuta et al., 1984). The experimental and epidemiological evidences strongly indicate that the liver fluke infection in the etiology of cholangiocarcinoma (CCA); the bile duct cancer (Thamavit et al., 1978; IARC, 1994). Multi-factorial etiology of CCA, mechanical 1 Parasitic Disease Research Unit, Suranaree University of Technology, 2 Institute of Medicine, Suranaree University of Technology, Muang, Nakornrachasima, 3 Department of Pathology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand *For correspondence: natthawut.k@sut.ac.th Abstract Background: Opisthorchis viverrini infection is a serious public-health problem in Southeast Asia. It is associated with a number of hepatobiliary diseases and the evidence strongly indicates that liver fluke infection is the etiology of cholangiocarcinoma. Objectives: This study aimed to investigate Opisthorchis viverrini metacercarial infection in cyprinoid fish collected from 32 districts of Nakhon Ratchasima province, Northeastern Thailand during one year period from February 2010 to February 2011. Methods: A cross-sectional study was conducted, data being collected with pepsin-HCl digestion and stereomicroscope, respectively. Analysis was performed using SPSS Windows Version 12.0. Results: A total of 640 Cyprinidae family fish including 5 species were collected from different study sites, and investigated for O. viverrini metacercariae. The infection rate was 12.3% (79/640), predominantly in Cyclocheilichthys armatus, C. repasson, Puntioplites proctzysron, Hampala macrolepitota and Hampala dispar, respectively. The prevalence of O. viverrini metaceria in Nakhon Ratchasima area was 78.1%, predominantly in Sida and KiaKham Thale So. Conclusion: This findings stress that natural fish species in rural communities are still a source of O viverrini infection and put local people at risk, therefore public awareness and prevention campaigns are urgently required. Keywords: Carcinogenic human liver fluke - metacercariae - Thailand RESEARCH COMMUNICATION Carcinogenic Human Liver Fluke: Current Status of Opisthorchis viverrini Metacercariae in Nakhon Ratchasima, Thailand Natthawut Kaewpitoon 1,2 *, Soraya J Kaewpitoon 1,2 , Naporn Ueng-arporn 1,2 , Ratana Rujirakul 1 , Seekaow Churproong 2 , Likit Matrakool 2 , Suprakrit Auiwatanagul 2 , Banchob Sripa 3 damage, parasite secretions, and immunopathology may enhance cholangiocarcinogenesis (Flavell, 1981; Sripa et a., 2007). The infection is associated with a number of hepatobiliary diseases, including cholangitis, obstructive jaundice, hepatomegaly, cholecystitis and cholelithiasis (Harinasuta et al., 1984). The pathogenesis of O viverrini-mediated hepatobiliary changes may be due to mechanical irritation caused by the liver fluke suckers and/ or its metabolic products (Bhamarapravati et al., 1978; Sriamporn et al., 2004). However, several authors suggest that immunopathological process may contribute to the hepatobiliary inflamation and damage (Tansurat, 1971; Viranuvatti & Stitnimankarn, 1972; Bhamarapravati et al., 1978; Pairojkul et al., 1991). The experimental and epidemiological evidence strongly implicate the liver fluke infection in the etiology of cholangiocarcinoma (CCA); the bile duct cancer (Thamavit et al., 1978; IARC, 1994). Multi-factorial etiology of CCA, mechanical damage,