title: Cercarial emergence patterns for Opisthorchis viverrini sensu lato infecting Bithynia siamensis goniomphalos from Sakon Nakhon Province, Thailand.
abstract: Opisthorchis viverrini sensu lato is a food-borne trematode which is classified as a class 1 carcinogen, with infection potentially leading to cholangiocarcinoma. Snails of the genus Bithynia act as the first intermediate hosts and an amplifying point in the parasite life cycle. In order to investigate seasonal effect on transmission dynamics of O. viverrini in Bithynia siamensis goniomphalos, cercarial emergence and output profiles were monitored at different season. A total of 4533 snails originating from Sakon Nakhon Province, Thailand, collected during the three main seasons, were analyzed for O. viverrini s.l.
  
  
  BACKGROUND
  Emergence of O. viverrini s.l. cercariae from snails was monitored daily from 06:00 to 18:00 h for seven consecutive days. The prevalence of infection in the snails was highest in the hot-dry season and declined in the rainy and cool-dry seasons. Peak cercarial emergence occurred between 08:00 and 10:00 h during the rainy and cool-dry seasons and between 10:00 and 12:00 h during the hot-dry season. The cercarial output was highest in the hot-dry season, similar to a previous study from Lao People's Democratic Republic (PDR). Average cercarial output/snail in Thailand was higher than in Lao PDR. The number of cercariae emerging from the snails was strongly related to snail size, but the relationship between prevalence of infection and snail size differed between seasons. Observed discrepancies in the emergence patterns and per capita cercarial release may reflect differences in environmental, snail, and/or parasite factors particularly biological characteristics between the cryptic species of O. viverrini s.l. and B. s. goniomphalos from Thailand and Lao PDR.
authors.affiliation: Department of Parasitology, Faculty of Medicine, Khon Kaen University, Khon Kaen, 40002, Thailand.|Department of Science, Faculty of Science and Engineering, Kasetsart University, Chalermphrakiat Sakon Nakhon Province Campus, Sakon Nakhon, 47000, Thailand.
authors.forename: Nonglak
authors.initials: N
authors.lastname: Laoprom
authors.affiliation: Department of Parasitology, Faculty of Medicine, Khon Kaen University, Khon Kaen, 40002, Thailand.|Liver Fluke and Cholangiocarcinoma Research Center, Faculty of Medicine, Khon Kaen University, Khon Kaen, 40002, Thailand.
authors.forename: Nadda
authors.initials: N
authors.lastname: Kiatsopit
authors.affiliation: Department of Parasitology, Faculty of Medicine, Khon Kaen University, Khon Kaen, 40002, Thailand. paib_sit@kku.ac.th.|Liver Fluke and Cholangiocarcinoma Research Center, Faculty of Medicine, Khon Kaen University, Khon Kaen, 40002, Thailand. paib_sit@kku.ac.th.|Cholangiocarcinoma Screening and Care Program (CASCAP), Khon Kaen University, Khon Kaen, 40002, Thailand. paib_sit@kku.ac.th.
authors.forename: Paiboon
authors.initials: P
authors.lastname: Sithithaworn
authors.affiliation: Department of Parasitology, Faculty of Medicine, Khon Kaen University, Khon Kaen, 40002, Thailand.|Liver Fluke and Cholangiocarcinoma Research Center, Faculty of Medicine, Khon Kaen University, Khon Kaen, 40002, Thailand.
authors.forename: Kulthida
authors.initials: K
authors.lastname: Kopolrat
authors.affiliation: Department of Parasitology, Faculty of Medicine, Khon Kaen University, Khon Kaen, 40002, Thailand.|Liver Fluke and Cholangiocarcinoma Research Center, Faculty of Medicine, Khon Kaen University, Khon Kaen, 40002, Thailand.
authors.forename: Jutamas
authors.initials: J
authors.lastname: Namsanor
authors.affiliation: Department of Parasitology, Faculty of Medicine, Khon Kaen University, Khon Kaen, 40002, Thailand.|Liver Fluke and Cholangiocarcinoma Research Center, Faculty of Medicine, Khon Kaen University, Khon Kaen, 40002, Thailand.|Cholangiocarcinoma Screening and Care Program (CASCAP), Khon Kaen University, Khon Kaen, 40002, Thailand.|Faculty of Medicine, Imperial College London, St Mary's Campus, South Wharf Street, London, W2 1NY, UK.
authors.forename: Ross H
authors.initials: RH
authors.lastname: Andrews
authors.affiliation: Cholangiocarcinoma Screening and Care Program (CASCAP), Khon Kaen University, Khon Kaen, 40002, Thailand.|Institute of Zoology 1: Ecology and Parasitology, University of Karlsruhe, Kornblumenstrasse 13, Karlsruhe, Germany.
authors.forename: Trevor N
authors.initials: TN
authors.lastname: Petney
mesh_terms: D000818:Animals; D009889:Opisthorchiasis / Q000469:parasitology*; D009891:Opisthorchis / Q000145:classification / Q000235:genetics / Q000302:isolation & purification* / Q000502:physiology; D012621:Seasons; D012908:Snails / Q000469:parasitology*; D013785:Thailand / Q000453:epidemiology
keywords: Bithynia siamensis goniomphalos; Cercarial emergence; Opisthorchis viverrini; Thailand