A new second intermediate host and phylogenetic relationships based on the ITS2 sequence of Isoparorchis sp. (Digenea: Isoparorchiidae) in Thailand

Abstract

Abstract The genus Isoparorchis (Family: Isoparorchiidae) contains trematodes infecting the air bladder of freshwater catfishes in Asia and Australia. Isoparorchis spp. rely on freshwater shrimps and fishes as intermediate hosts. There is limited information about parasitic infections in freshwater shrimp in Thailand, and Isoparorchis infection in an intermediate host in this country has never been reported. Thus, this study reports infections in freshwater shrimp (Macrobrachium lanchesteri and Caridina sp.), including overall prevalence, mean intensity, morphological characters and molecular analyses. The parasite specimens were analysed by studying their morphological characters, together with a molecular approach based on internal transcribed spacer 2 (ITS2) sequence data. The overall prevalence and mean intensity of Isoparorchis infections were 92% and 1.89, respectively. The metacercariae were identified as Isoparorchis sp. based on their morphological characters and supported by the comparison with published ITS2 sequences of Isoparorchis species. The phylogenetic studies based on the ITS2 region demonstrated that all of the Isoparorchis sp. specimens in this study are distinct from Isoparorchis species in previous reports. Moreover, we show for the first time that the freshwater shrimp M. lanchesteri serves as a second intermediate host of Isoparorchis sp. and we provide a morphological description and molecular characterization of Isoparorchis sp. metacercariae based on ITS2 sequence data to clarify the status of Isoparorchis sp. in Thailand.