Infection status with zoonotic trematode metacercariae in fish from Lao PDR

Studies on the infection status with fishborne zoonotic trematode (FZT) metacercariae were reviewed with our data, which obtained from the fish survey in 8 administrative localities, i.e., Vientiane Municipality, Luang Prabang, Xieng Khouang, Vientiane, Khammuane, Savannakhet, Saravane and Champasak Provinces of Lao PDR (Laos) in 10 times. Total 1046 freshwater fishes (69 species) were examined with the artificial digestion method from 2002 to 2011. Total 6 species of zoonotic trematode, i.e., Opisthorchis viverrini, Haplorchis taichui, Haplorchis yokogawai, Haplorchis pumilio, Centrocestus formosanus and Procerovum varium, metacercariae were detected in fishes from Laos. The metacercariae of O. viverrini were detected in 284 (37.9%) out of 749 fishes (26 spp.), and their average density was 297 per fish infected. The prevalences of 4 heterophyid species, i.e., H. taichui, H. yokogawai, H. pumilio and C. formosanus, metacercariae were 45.4% (out of 941 fishes in 46 spp. examined), 45.1% (811 fishes in 35 spp.), 8.8% (457 fishes in 11 spp.) and 18.1% (475 fishes in 13 spp.), their average densities were 291, 218, 4 and 15 per fish infected respectively. The endemicities of O. viverrini metacercariae were much higher in fishes from Savannakhet Province and Vientiane Municipality (2002). Those of H. taichui metacercariae were much higher in fishes from Khammuane and Luang Prabang (2011) Provinces. By the present study, it was confirmed that some species of FZT metacercariae are highly prevalent in fishes from Laos.