Prevalence of Opisthorchis viverrini infection in humans and fish in Kratie Province, Cambodia

Opisthorchis viverrini is a medically important foodborne parasite in the Indochina Peninsula. In Cambodia, the prevalence of this trematode has been reported in Takeo Province, but not in other areas. In this study, we investigated the prevalence of O. viverrini infection among people in seven riparian villages along the Mekong River, Kratie Province. We also examined the status of metacercarial infection in fish hosts. Fecal specimens were collected from 2101 residents and schoolchildren, and were examined by the Kato-Katz technique. The average O. viverrini egg positive rate was 4.6%, with the highest prevalence found in Roka Kandal A village (10.4%) followed by Talous village (5.9%). In these villages, adult residents showed higher prevalences (19.4% and 9.0%, respectively) than schoolchildren (6.4% and 1.4%, respectively). O. viverrini adult worms were recovered from 2 egg-positive cases (18 and 4 specimens) after praziquantel treatment and purgation. In addition, three of seven freshwater fish species caught near the villages were positive for O. viverrini metacercariae. A total of 367 metacercariae were harvested from 19 infected fish (metacercarial density; 19 per fish). The species of the metacercariae was confirmed through adult worm recovery by experimental infection to hamsters. The results provide evidence that the surveyed areas of Kratie Province, Cambodia, are endemic for O. viverrini infection.