title: Fish sharing as a risk factor for Opisthorchis viverrini infection: evidence from two villages in north-eastern Thailand.
abstract: BACKGROUND
  Foodborne trematodiasis (FBT) is a significant global health problem, with the liver flukes Opisthorchis viverrini, O. felineus, and Clonorchis sinensis contributing to half of the global burden of FBT. North-eastern Thailand where O. viverrini is endemic and un-cooked fish dishes remain an integral part of the food culture has the highest reported incidence of opisthorchiasis, including associated cholangiocarcinoma. Both food sharing and eating practices are potentially important factors in FTB, suggesting an important role for the social ecology of disease transmission in these rural communities.
  
  
  METHODS
  Two rural Thai-Lao villages that were part of a 12-village project in Northeastern Thailand were selected for detailed investigation of O. viverrini infection risk associated with sharing of raw fish dishes among households. The project included screening individuals for infection and cholangiocarcinoma, a household questionnaire, and offering treatment options for positive individuals. Social network mapping was used to construct raw fish dish-sharing networks and create a proxy variable capturing variability in the degree of food sharing (DFS), measured as the number of different households with which each household shared fish dishes. Measures of associations between DFS, O. viverrini infection, the frequency of raw fish consumption, and the number of raw fish dishes consumed were generated using binary logistic regression, proportional odds ordinal logistic regression, and Poisson regression.
  
  
  RESULTS
  The results showed that the probability that a household has members infected with O. viverrini increased by ~7% (P < 0.01) for each additional household included in its network. Moreover, the frequency and number of types of raw fish dishes consumed increased significantly as the DFS increased. Of the two villages, that with the highest infection prevalence (48% versus 34.6%) had significantly higher social connectivity overall (P < 0.001).
  
  
  CONCLUSIONS
  Our findings suggest that the social ecology of human settlements may be key to understanding the transmission dynamics of some FBT. In the case of O. viverrini in Thai-Lao communities, for which food sharing is a traditional practice supporting social cohesion, food sharing network mapping should be incorporated into community-based interventions. These should encourage fish dish preparation methods that minimize infection risk by targeting households with high DFS values.
authors.affiliation: WHO Collaborating Centre for Research and Control of Opisthorchiasis (Southeast Asian Liver Fluke Disease), Tropical Disease Research Laboratory, Department of Pathology, Faculty of Medicine, Khon Kaen University, 123 Mittraparb Road, Khon Kaen, 40002, Thailand.|Present Address: Faculty of Education, Khon Kaen University, Khon Kaen, Thailand.
authors.forename: Parichat
authors.initials: P
authors.lastname: Saenna
authors.affiliation: Biostatistics Center of Excellence, Faculty of Medicine, Chulalongkorn University, Bangkok, 10330, Thailand.
authors.forename: Cameron
authors.initials: C
authors.lastname: Hurst
authors.affiliation: WHO Collaborating Centre for Research and Control of Opisthorchiasis (Southeast Asian Liver Fluke Disease), Tropical Disease Research Laboratory, Department of Pathology, Faculty of Medicine, Khon Kaen University, 123 Mittraparb Road, Khon Kaen, 40002, Thailand.|Global Health Asia, Integrative Research and Education Program, Faculty of Public Health, Mahidol University, Bangkok, Thailand.|Department of Biology, Laurentian University, 935 Ramsey Lake Road, Sudbury, P3E2C6, ON, Canada.
authors.forename: Pierre
authors.initials: P
authors.lastname: Echaubard
authors.affiliation: WHO Collaborating Centre for Research and Control of Opisthorchiasis (Southeast Asian Liver Fluke Disease), Tropical Disease Research Laboratory, Department of Pathology, Faculty of Medicine, Khon Kaen University, 123 Mittraparb Road, Khon Kaen, 40002, Thailand.|Global Health Asia, Integrative Research and Education Program, Faculty of Public Health, Mahidol University, Bangkok, Thailand.
authors.forename: Bruce A
authors.initials: BA
authors.lastname: Wilcox
authors.affiliation: WHO Collaborating Centre for Research and Control of Opisthorchiasis (Southeast Asian Liver Fluke Disease), Tropical Disease Research Laboratory, Department of Pathology, Faculty of Medicine, Khon Kaen University, 123 Mittraparb Road, Khon Kaen, 40002, Thailand. banchob@kku.ac.th.
authors.forename: Banchob
authors.initials: B
authors.lastname: Sripa
mesh_terms: D000328:Adult; D000818:Animals; D001650:Bile Duct Neoplasms / Q000150:complications / Q000469:parasitology / Q000517:prevention & control; D018281:Cholangiocarcinoma / Q000150:complications / Q000469:parasitology / Q000517:prevention & control; D005260:Female; D005399:Fishes / Q000469:parasitology*; D005517:Foodborne Diseases / Q000453:epidemiology / Q000469:parasitology / Q000517:prevention & control; D005618:Fresh Water / Q000469:parasitology; D006801:Humans; D008297:Male; D008875:Middle Aged; D009889:Opisthorchiasis / Q000453:epidemiology / Q000469:parasitology* / Q000517:prevention & control / Q000635:transmission*; D009891:Opisthorchis / Q000302:isolation & purification*; D015995:Prevalence; D066256:Raw Foods / Q000469:parasitology; D012307:Risk Factors; D012931:Social Environment; D060756:Social Networking; D011795:Surveys and Questionnaires; D013785:Thailand / Q000453:epidemiology; D055815:Young Adult
keywords: Food sharing; Foodborne trematodes; Opisthorchiasis prevention and control; Opisthorchis viverrini; Raw fish dishes; Social network analysis; Thailand