Opisthorchis viverrini metacercariae in cyprinoid fish from three rivers in Khammouane Province, Lao PDR.

his study aimed to determine the prevalence, intensity and distribution of Opisthorchis viverrini metacercarial infection in cyprinoid fish collected from three rivers in Khammouane Province, central Lao PDR, between April 2007 and February 2008. A total of 1,356 freshwater fish were collected; of these, 1,246 cyprinoid fish of 18 species were examined for O. viverrini metacercariae–only 8 species of cyprinoid fish were infected with O. viverrini metacercariae. Infection rates were as follows: Cyclocheilichthys repasson (58.5%), C. armatus (43.1%), C. enoplos (10.0%), Dangila lineata (69.6%), Henicorhynchus lineatus (42.9%), Hampala dispar (44.4%), Puntioplites proctzysron (26.8%), Osteochilus waandersii (30.5%); and the mean ± SD intensities of infection were 2.63 ± 1.11, 1.05 ± 0.53, 0.90 ± 0.43, 2.60 ± 0.98, 2.4 ± 0.98, 0.92 ± 0.53, 0.93 ± 0.48, and 1.90 ± 0.45, respectively. The prevalence of O. viverrini metacercarial infection among cyprinoid fish from Namdone and Napakane increased markedly during the dry season. O. viverrini metacercariae were found scattered throughout the entire body; however, the body muscles harbored the highest density of metacercariae, followed by the fins, head, and visceral organs, respectively.