Opisthorchis felineus and Metorchis bilis Metacercariae in Cyprinid Fish Leuciscus idus in Nura-Sarysu River, Kazakhstan

Molecular genetic species definition of Opisthorchiidae-like cercariae from Bithyniidae snails of Chany Lake (South-Western Siberia, Russia)

The studies of opisthorchiids larval stages associated with Bithyniidae snails can provide important and the most reliable data for opisthorchiidoses foci characterization due to the low mobility of such opisthorchiid's host species as Bithyniidae snails. The foci of opisthorchiosis (caused by Opisthorchis felineus) and metorchiosis (caused by Metorchis bilis) are overlapping in the basins of the Ob and Irtysh Rivers. Thus, difficulties with determining the species of cercariae significantly reduce the accuracy of epidemiological conclusions regarding opisthorchiosis, which has a much higher medical significance. Moreover, M. bilis cercariae identification is complicated by the fact that the focus of metorchiosis caused by Metorchis xanthosomus (infecting fish-eating predatory birds) occurs on the same territory. In this study, we for the first time carried out the molecular genetic identification of West-Siberian opisthorchiid cercariae to verify morphological identification and confirmed O. felineus's main association with Bithynia troschelii snail and M. bilis'-with B. tentaculata snail. Thus, our study applied a two-stage approach: the morphological identification of any opisthorchiid-like cercariae in Bithynia snails and subsequent molecular genetic precise species determination of cercariae in the reduced samples.

Fish-borne trematode infections in wild fishes in Bangladesh

Fish-borne liver and intestinal flukes are helminth pathogens that have a negative impact on public health worldwide. We herein investigated the status of infection by the metacercariae (MC) of fish-borne trematodes (FBTs) in randomly selected freshwater wild fishes. Five species of fishes were collected and digested artificially using digestion fluid to recover MC. All fish species, namely, ticto barb (Puntius ticto) (14/16, 87.5%), banded gourami (Colisa fasciata) (8/12, 66.7%), freshwater garfish (Xenentodon cancila) (9/14, 64.3%), flying barb (Esomus danricus) (5/12, 41.7%), and reba carp (Cirrhinus reba) (7/11, 63.7%), were infected with FBTs. The overall infection rate was 66.2% and the mean intensity was 748.3 ± 2947.5 MC/100 g of fishes. The loads of MC in ticto barb, reba carp, freshwater garfish, banded gourami, and flying barb per 100 g of fishes were 1978.8 ± 5053.7, 268.3 ± 440.7, 140 ± 105.4, 134.3 ± 109.2, and 117.6 ± 102.3, respectively. The infection rate was significantly higher (P < 0.05) in the body (55.4%) than in the head (40%) of fishes. Morphological and morphometrical analyzes identified the MC of Clonorchis spp., Opisthorchis spp., Metorchis spp., Metagonimus spp., and Echinostoma spp. Collectively, the present results suggest that wild freshwater fishes are important intermediate hosts for FBTs, and play a critical role in the transmission cycle of these parasites in Bangladesh. The results also indicate that people of the country are at risk of these infections.