Insights on foodborne zoonotic trematodes in freshwater snails in North and Central Vietnam

Abstract

Foodborne zoonotic trematode (FZT) infections are common neglected tropical diseases in Southeast Asia. Their complicated life cycles involve freshwater snails as intermediate hosts. A cross-sectional study was conducted in Yen Bai and Thanh Hoa provinces in North and Central Vietnam, to investigate the diversity of cercariae of potential FZT and to construct the phylogenetic relationship of trematode cercariae based on the Internal Transcribed Spacer 2 (ITS2) region. Among 17 snail species collected from various habitats, 13 were infected by 10 cercarial groups among which parapleurolophocercous, pleurolophocercous, and echinostome cercariae were of zoonotic importance. The monophyletic tree separated cercarial sequences into different groups following the description of the cercariae families in which Haplorchidae, Opisthorchiidae, Echinochasmidae, and Echinostomatidae are important families of FZT. The overall prevalence was different among snail species and habitats and showed a seasonal trend. Parapleurolophocercous and echinostome cercariae emerged as the most common cercariae in snails in Yen Bai, while monostome, echinostome, and megalura cercariae were most common in Thanh Hoa. Using a molecular approach, we identified Parafossarulus striatulus as the first intermediate snail host of Clonorchis sinensis in Thac Ba Lake. Melanoides tuberculata and Bithynia fuchsiana were we identified preferred intermediate snail hosts of a diverse range of trematode species including intestinal flukes (i.e., Haplorchis pumilio and Echinochasmus japonicus) in Yen Bai and Thanh Hoa, respectively.

Molecular identification of trematode parasites infecting the freshwater snail Bithynia siamensis goniomphalos in Thailand

“…The next-best 28S matches were much lower (∼87%) and were with campulids, brachycladiids and acanthocolpids, none of which is a likely home for this cercaria. The ITS2 region (ON312609) had a 98.59% similarity with that of a parapleurolophocercous cercaria from Vietnam (MT268100), reported by Nguyen et al (2021), possibly from Bithynia fuchsiana Möllendorff, 1888 (host identity not very clear from the paper). No other full-length ITS2 matches were found using BLAST.…”

“…Our ITS2 sequence (ON312607) had a 100% match with that of C. vietnamensis. There was also a 100% match with a sequence (MT268104: Nguyen et al, 2021) from a cercaria from Vietnam (host unclear, but likely a bithyniid), and 100% match with a monostome cercaria from B. s. siamensis near Bangkok (Wiroonpan et al, 2021). Ito et al (1962) recorded a monostome cercaria (which he identified rather tentatively as that of Notocotylus attenuatus Rudolphi, 1809) from B. funiculata from Thailand.…”

Vietnam: Neglected tropical diseases in an emerging and accelerating economy

“…The prevalence of food-borne trematodes, especially liver fluke infection caused by Opisthorchis viverrini or Clonorchis sinensis , and intestinal fluke infections caused by Fasciolopsis buski , has increased [ 58 , 59 ]. Liver fluke is also an important cause of cholangiocarcioma.…”

“…In a study conducted in Northern Vietnam, older individuals knew this risk and continued eating raw fish, because they knew drug treatment was available [ 62 ]. Many traditional dishes also utilize raw fish [ 58 ]. Furthermore, 25.8% of household members were found to have not eaten raw fish, but were infected due to cross-contamination via sharing food [ 62 ].…”

Monsters in our food: Foodborne trematodiasis in the Philippines and beyond

“…Foodborne trematodiasis is a group of zoonotic parasitoses caused by flukes that are vehicled by poorly prepared food items (Keiser and Utzinger, 2009;Lu et al, 2018;Betson et al, 2020). This group of parasitic infections is one of the illnesses classified by the World Health Organization as Neglected Tropical Diseases (NTDs) (Engels and Zhou, 2020;Nguyen et al, 2021;Casulli, 2021). NTDs plague impoverished, rural areas in developing countries where hygienic practices and cultural eating behaviors are conducive to their perpetuation (Belizario et al, 2013;Engels and Zhou, 2020).…”