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Snails are the first intermediate host in the life cycle of trematodes. Previous research found that Trichopodus microlepis fish, cultured in earthen ponds in Tan Nhut Commune, Binh Chanh District, Ho Chi Minh City, Vietnam had a high infection rate with metacercariae of Centrocestus formosanus and Procevorum sp. It is necessary to investigate whether habitats supplying water to the ponds may contribute to the transmission by carrying intermediate hosts and/or cercariae into these ponds or not. A study of cercariae and snail composition in rice fields and canal supplying water directly to these Trichopodus microlepis ponds was carried out with six samplings in the years 2022 and 2023. A total of 1,151 snails were collected, and nine snail species belonging to 8 genera and 6 families were identified. Three snail species in both rice fields and canal were infected with trematode (cercariae stage) including Bithynia siamensis, Lymnaea viridis and Indoplanorbis exustus. The overall prevalence in the dry season (25.9%) was significantly higher than in the wet season (10.6%) (P<0.05). Three cercariae morphotypes were recovered from snails: xiphidio (in all three snails), echinostome (in Lymnaea viridis and Indoplanorbis exustus), and pleurolophocercous in Bithynia siamensis. This finding shows that Bithynia siamensis is one of the infected sources for Trichopodus microlepis fish cultured in ponds, as pleurolophocercous is also the cercariae in the family of Heterophyidae (including Centrocestus formosanus and Procevorum sp.). Further research should be done to clarify the transmission of fish-borne zoonotic diseases to cultured Trichopodus microlepis in other habitats including the actual fishponds, and sources of trematodes in order to produce Trichopodus microlepis free of metacercariae, contributing to clean aquaculture development and

A study on trematode obtained from freshwater snails in 30 grow-out giant gourami ponds supplied by well water was conducted in Chau Thanh district, Tien Giang province, Vietnam. The snails were sampled in the flooding season (October 2020), the intermediary season (January 2021) and the non-flooding season (April 2021). Eight snail species belonging to 8 genera, 4 families were found including Sermyla tornatella (48.6%), Sinotaia lithophaga (19.3%), Filopaludina sumatrensis (15.4%), Melanoides tuberculata (6.4%), Pomacea sp. (4.7%), Bithynia siamensis (4.2%), Thiara scabra (0.8%) and Tarebia granifera (0.6%). Cercariae were recovered from only two snail species of Melanoides tuberculata with Xiphidio cercariae and Furcocercous cercariae with a prevalence of 7.4%, and Bithynia siamensis with Xiphidio cercariae and Pleurolophocercous cercariae with the infection rate of 6.9%. The trematodes were found in 8 ponds (26.7%), 7 ponds (23.3%), and 3 ponds (10.0%) in the intermediary season, the non-flooding season, and the flooding season, respectively (P>0.05). More research on the epidemiology of trematodes in snails in fishponds should be done to contribute to food safety and sustainable aquaculture.