Prevalence and Factors Associated with Opisthorchis Viverrini Infection in Lao PDR

In many countries of South-East Asia infection with the liver fluke Opisthorchis viverrini (OV) is of considerable importance as a risk factor for cholangiocellular carcinoma (CC) development (Haswell-Elkins et al., 1994; Sriamporn et al., 2004; Sripa et al., 2011). In Viet Nam, Clonorchis sinensis may also be found (Doanh and Nawa, 2016). Infection with liver flukes (Opisthorchis viverrini, Opisthorchis felineus and Clonorchis sinensis) has been determined to be a class I carcinogen by the International Agency for Cancer Research evaluation committee (IARC, 1994). It has proved very difficult to change the dietary lifestyle habit of eating raw fish containing liver fluke eggs (Jongsuksuntigul and Imsomboon, 2003; Sripa et al., 2011) and a complicating factor is the presence of reservoir canine and feline hosts (Enes et al., 2010; Aunpromma et al., 2012). Furthermore, while the antihelminthic drug praziquantel may be used to control OV infection it maygive rise to an unwise dependency (Saengsawang et al., 2013) and repeated cycles of re-infection and treatment with praziquantel may increase the risk of CC (Kamsa-ard et al., 2015). As in neighbouring Thailand and Cambodia (Sithithaworn et al., 2012), OV has long been known in Laos (Bedier and Chesnau, 1929) and more recent reports have confirmed its presence as a common parasite in central and southern parts of the country ( Kobayashi et