title: Field survey focused on Opisthorchis viverrini infection in five provinces of Cambodia.
abstract: BACKGROUND
  Opisthorchiasis is endemic in Thailand and Lao People's Democratic Republic and constitutes a major public health problem throughout the Mekong Basin. Although Cambodia is located in the Mekong Basin, the status of O. viverrini infection in that country was not previously clarified. This research was conducted to document the extent and distribution of O. viverrini infection in Cambodia.
  
  
  METHODS
  Surveillance was conducted in 55 villages in five Cambodian provinces. Research tools included stool examination using the Kato-Katz thick-smear technique, identification of intermediate hosts, and interviews covering factors related to O. viverrini infection. Some larvae and egg-positive stool samples were examined using PCR to detect O. viverrini DNA.
  
  
  RESULTS
  A total of 16,082 stool samples from the 55 villages were examined, of which 1232 were egg positive. In 15 villages with egg-positive rates of greater than 10%, eggs were found in 998 of 3585 stool samples, for an egg-positive rate of 27.8%. PCR analysis showed that 30 of 33 samples were positive for O. viverrini DNA from five villages in Kampong Cham and Kampong Thom provinces. The first intermediate host Bithynia siamensis siamensis was identified in the target areas of Takaev, Kandal, and Kampong Cham provinces. Cercariae were identified morphologically as O. viverrini and some were confirmed using PCR. Metacercariae of O. viverrini were identified by morphologic observations, animal experiments, or PCR in six species of fish in the target areas.
  
  
  CONCLUSIONS
  Four Cambodian provinces were identified as endemic areas of O. viverrini infection. Careful planning is necessary for effective field surveys, because complex environmental factors might be involved in the distribution of O. viverrini infection-endemic areas in Cambodia. Many problems remain to be resolved regarding the status of O. viverrini infection in Cambodia, and a nationwide baseline survey is necessary.
authors.affiliation: School of Nursing, Dokkyo Medical University Tochigi, Japan. Electronic address: mkazu@dokkyomed.ac.jp.
authors.forename: Kazuko
authors.initials: K
authors.lastname: Miyamoto
authors.affiliation: Laboratory of Tropical Medicine and Parasitology, Dokkyo Medical University, Tochigi, Japan.
authors.forename: Masashi
authors.initials: M
authors.lastname: Kirinoki
authors.affiliation: Center for International Cooperation, Dokkyo Medical University, Tochigi, Japan.
authors.forename: Hajime
authors.initials: H
authors.lastname: Matsuda
authors.affiliation: Laboratory of Tropical Medicine and Parasitology, Dokkyo Medical University, Tochigi, Japan.
authors.forename: Naoko
authors.initials: N
authors.lastname: Hayashi
authors.affiliation: Laboratory of Tropical Medicine and Parasitology, Dokkyo Medical University, Tochigi, Japan.
authors.forename: Yuichi
authors.initials: Y
authors.lastname: Chigusa
authors.affiliation: National Center for Malaria Control, Parasitology and Entomology (CNM), Ministry of Health (MOH), Cambodia.
authors.forename: Muth
authors.initials: M
authors.lastname: Sinuon
authors.affiliation: National Center for Malaria Control, Parasitology and Entomology (CNM), Ministry of Health (MOH), Cambodia.
authors.forename: Char Meng
authors.initials: CM
authors.lastname: Chuor
authors.affiliation: Former Head, Department of Social and Environmental Medicine, Faculty of Tropical Medicine, Mahidol University, Thailand.
authors.forename: Viroj
authors.initials: V
authors.lastname: Kitikoon
mesh_terms: D000328:Adult; D000818:Animals; D002160:Cambodia / Q000453:epidemiology; D005243:Feces / Q000469:parasitology; D005260:Female; D005399:Fishes; D016266:Food Parasitology; D006801:Humans; D008297:Male; D008647:Mesocricetus; D009891:Opisthorchis / Q000302:isolation & purification*; D010270:Parasite Egg Count; D012499:Sanitation
keywords: Cambodia; Endemic infection; Opisthorchis viverrini