DOI:10.22034/APJCP.2017.18.10.2853 Epidemiology of Opisthorchis viverrini in Udon Thani RESEARCH ARTICLE A Large Scale Study of the Epidemiology and Risk Factors for the Carcinogenic Liver Fluke Opisthorchis viverrini in Udon Thani Province, Thailand Suksanti Prakobwong1,2*, Apiporn Suwannatrai3, Achara Sancomerang4, Suwit Chaipibool5, Ngampis Siriwechtumrong6 Abstract Opisthorchis viverrini infection and cholangiocarcinoma are serious problems in South East Asia. This study aimed to find the prevalence of opisthorchiasis in various hosts in Udon Thani Province. Total fecal samples were collected from 14,766 participants. The epidemiological data collected and analysed included prevalence and intensity of infection. Odds ratios (OR) were calculated to determine the associations between cross sectional data and to predict possible risk factors. The prevalence of O. viverrini infection in Udon Thani Province averaged 15.3% (eggs per gram (epg.) = 48.9 and range; 12-1,320), with differences between villages (range; 3.8%-79.8%). An age-dependence for infection was observed to increase from ages 25 to 50 years and then decrease for older participants. A univariate analysis identified risk parameters including age (p = 0.040; OR = 3.9 (95% CI = 1.2-7.5)), education (p<0.0001; OR = 7.3 (95% CI = 1.8-21.6)) and eating habits (p = 0.032; OR = 1.6 (95% CI = 0.5-3.7)). Interestingly, most participants were not aware of treatments such as praziquantel (p< 0.0001; OR = 3.5 (95% CI = 1.4-11.6)), had no history of parasitic treatment (p = 0.486; OR = 1.5 (95% CI = 0.5-3.5)) and had eaten raw fish (p = 0.04; OR = 7.4 (95% CI = 1.5-18.6)). Liver fluke infection in dogs (18.1%, epg. = 44.7, range; 32-96) was significantly higher than in cats (11.0%, epg. = 117.8, range; 44-372) (p<0.05). A positive association between O. viverrini infection in dogs and their owners was found. In addition, cyprinid fish dominantly infected by metacercaria including Henicorhynchus siamensis (27.7%), Cyclocheilichthys repasson (21.9%), Hampala dispar (14.1%), and Barbonymus gonionotus (6.9%). This study provides basic information required for the development of future effective and sustainable strategies to reduces infection rates, mainly by providing health education and encouraging behavioural changes. Keywords: Opisthorchis viverrini- epidemiology- risk factors Asian Pac J Cancer Prev, 18 (10), 2853-2860 Introduction O. viverrini infection in definitive and reservoir hosts was occurring as a result of consuming raw or uncooked Chronic Opisthorchis viverrini infection is a critical risk fish which contain the infective metacercaria (Sripa et factor for hepatobiliary diseases and cholangiocarcinoma al., 2007). The parasite migrates to the intrahepatic bile (CCA), which are health problems across South-East ducts via the common bile duct and produces eggs that Asia, including Thailand, Laos People’s Democratic are excreted in the feces after approximately 30 days Republic, Cambodia and central Vietnam (Sripa et al., (Harinasuta and Harinasuta, 1984). Many reports have 2007). In this endemic area at least 6 million are estimated shown that the prevalence of O. viverrini in North-East to be infected and without diagnosis and treatment risk Thailand has gradually decreased over thirty years progression to CCA (Jongsuksuntigul and Imsomboon, from 34.6% to 10-15% depending on the area sampled 2003). In addition, people traditionally eat fermented (Jongsuksuntigul and Imsomboon, 2003), however fishes containing high concentrations of nitrosamines the infection percentage has gone no lower than 10% which are potent human carcinogens (Thamavit et al., in the endemic areas (Kaewpitoon et al., 2015). This 1993). Despite recent reports indicating that highly may be due to the control strategies of recent decades effective antiparasitic treatments are frequently used, the being concentrated only on human infection. However, prevalence and reinfection rates for liver fluke are still it is well known that the O. viverrini life cycle can also high (Saengsawang et al., 2017). involve domestic reservoir hosts, such as dogs and cats 1Department of Biology, 2Northeast Liver Fluke Research and Outreach Unit, Faculty of Science, Udon Thani Rajabhat University, 4Na-Di Hospital of Health Promotion, Muang district, 5Nong-Sang Hospital of Health Promotion, Nong Wua Sor district, 6Khu-Kaew Hospital, Provincial Health Office, Ministry of Public Health, Udon Thani, 3Department of Parasitology, Faculty of Medicine, Khon Kaen University, Khon Kaen, Thailand. *For Correspondence: [email protected] Asian Pacific Journal of Cancer Prevention, Vol 18 2853 Suksanti Prakobwong et al (Sithithaworn and Haswell-Elkins, 2003). Despite, the Province along the Huay Luang and Song Kram rivers, human opisthorchiasis was treated but the food-borne the Nong Han wet lands and the Nam Pan reservoir. Fecal parasitic zoonosis is a complete epidemiological cycle samples were collected from 14,766 participants living by facilitating return to human, which is still certain this in 176 villages of which 5,659 were males and 9,907 phenomenon in endemic countries. were females, with an age range spanning 25-76 years. The critical risk factors for O. viverrini infection The study protocol was approved by the Human Ethics are mainly associated with eating raw or uncooked fish Committee of Udon Thani Provincial Health Office, in many traditional fish dishes. There is evidence that Ministry of Public Health, Thailand. Letters explaining the 25 - 28 % of cyprinid fish were infected in the 13 provinces aims of the study and the strategies to be followed were of the North-East region surveyed in the last decade. sent to village heads, community leaders and to individual However, the rates of metacercaria infection was less households. Visits were made to each village to explain and steady at about 12.4% in Nakonrachasima Province, the benefits of the survey and the national program. Risk elsewhere in Thailand (Kaewpitoon et al., 2012a), 14.5% factors for liver fluke infection were assessed by using in 3 provinces of Lao PDR (Rim et al., 2013), 1.9% questionnaires to gather information about the age, sex, in Vietnam (Thu et al., 2007) and 2.1% in Cambodia occupation, knowledge of parasitic treatments and eating (Touch et al., 2009). Species diversity and an abundance behaviors of the participants. of cyprinid fishes in the North-East of Thailand and Fecal samples from domestic dogs (341) and cats advantageous environmental conditions in certain seasons (118) were collected from within 28 villages along the support the host-parasite population (Donthaisong et al., Huay Luang river basin. Only stools from domestic dogs 2016). A previous survey revealed a seasonal variation for and cats which had been confined to the house of their O. viverrini metacercaria infection in cyprinid fish with owners were collected thus allowing the fecal sample a peak in the dry season which may further increase the results to be correlated with the data obtained from the possibility of transmission (Sithithaworn et al., 1997). human occupants of the same house. The Animal Ethics In addition, differences in education, social practices, Committee of Udon Thani Rajabhat University also economy and life styles amongst communities change approved this part of the study. the patterns of risk to eat inadequately cooked fish (Sripa Humans and host reservoirs that were found to be et al., 2017). The risk factors in each area also need to parasitized by all species were treated with appropriate be identified. parasitic drugs and included in the active prevention and In Udon Thani Province, the prevalence of O. viverrini control program as part of the research strategy of the was reported in 2003 at 19% and the highest CCA ratio Faculty of Science, Udon Thani Rajabhat University. (44 : 100,000) was reported in the North-East (Sripa et al., 2003). However, a lack of epidemiological data has not A modified formalin ethyl-acetate concentration technique allowed the situation in the last decade to be clarified. In A quantitative modified formalin ethyl-acetate addition, the risk factor and complete epidemiological data concentration technique was used with slight modification. for existing parasitic cycles in intermediated and reservoir One gram of feces was fixed in 10% formalin and filtered hosts have never been simultaneously determined in through 2 layers of gauze after which the suspension was each endemic area. Therefore, the increased risk of centrifuged at 2,500 rpm for 3 minutes. The pellet was opisthorchiasis-associated CCA still remains as a result re-suspended with 10 ml of 10% formalin and 3 ml of of imprecise prevention and control strategies. ethyl-acetate and again centrifuged at 2,500 rpm for 3 This study aimed to perform a large scale integrated minutes. The floating liquid lipid in the supernatant was study of the prevalence and intensity of O. viverrini removed by tearing the inside of the tube. To the sediment infection in residents and reservoir hosts including was added 1 ml of 10% formalin and the number of eggs domestic dogs and cats and at the infective stage per gram of feces due to liver fluke infection was measured (metacercaria) in cyprinid fishes in Udon Thani Province, and confirmed by two experienced researchers. an upper part of North-East, Thailand. Samples were collected from 176 villages and the number of eggs per Isolation of metacercariae from cyprinid fish gram of feces (epg.) was measured by a modified formalin Cyprinid fish have traditionally been caught by ethyl-acetate concentration technique. The prevalence villagers from wet lands, rivers, dams and reservoirs and density of metacercaria were determined monthly by in Udon Thani Province. This study was conducted conventional 0.25% pepsin digestion. monthly between August 2016 and July 2017. O. viverrini metacercariae were isolated from naturally infected fish Materials and Methods by pepsin digestion as described previously (Pinlaor et al., 2013).