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Morphological and molecular characterization of lymnaeid snails and their potential role in transmission of Fasciola spp. in Vietnam.

ABSTRACT: Freshwater snails of the family Lymnaeidae play an important role in the transmission of fascioliasis worldwide. In Vietnam, 2 common lymnaeid species, Lymnaea swinhoei and Lymnaea viridis, can be recognized on the basis of morphology, and a third species, Lymnaea sp., is known to exist. Recent studies have raised controversy about their role in transmission of Fasciola spp. because of confusion in identification of the snail hosts. The aim of this study is, therefore, to clarify the identities of lymnaeid snails in Vietnam by a combination of morphological and molecular approaches. The molecular analyses using the second internal transcribed spacer (ITS2) of the nuclear ribosomal DNA clearly showed that lymnaeids in Vietnam include 3 species, Austropeplea viridis (morphologically identified as L. viridis), Radix auricularia (morphologically identified as L. swinhoei) and Radix rubiginosa (morphologically identified as Lymnaea sp.). R. rubiginosa is a new record for Vietnam. Among them, only A. viridis was found to be infected with Fasciola spp. These results provide a new insight into lymnaeid snails in Vietnam. Identification of lymnaeid snails in Vietnam and their role in the liver fluke transmission should be further investigated.

SUBMITTER: Dung BT

PROVIDER: S-EPMC3916454 | biostudies-literature | 2013 Dec

REPOSITORIES: biostudies-literature

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Morphological and molecular characterization of lymnaeid snails and their potential role in transmission of Fasciola spp. in Vietnam.

Dung Bui Thi BT Doanh Pham Ngoc PN The Dang Tat DT Loan Ho Thi HT Losson Bertrand B Caron Yannick Y

The Korean journal of parasitology 20131231 6

Freshwater snails of the family Lymnaeidae play an important role in the transmission of fascioliasis worldwide. In Vietnam, 2 common lymnaeid species, Lymnaea swinhoei and Lymnaea viridis, can be recognized on the basis of morphology, and a third species, Lymnaea sp., is known to exist. Recent studies have raised controversy about their role in transmission of Fasciola spp. because of confusion in identification of the snail hosts. The aim of this study is, therefore, to clarify the identities ...[more]

PMID: 24516270

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Project description:Background and objectivesLymnaeid snails are the known intermediate hosts of the liver fluke Fasciola spp. and therefore play an important role in the parasite's life cycle. The study is conducted to determine specificity of snail host-parasite interaction and to determine the snail-trematode infection rate by cercarial emergence, characterizing the emerging larvae using standardized key.Materials and methodsA total of 750 snails were collected from a rice field in Barangay Cawongan, Padre Garcia, Batangas, from November 2016 to March 2017 (n=150/month). Preliminary snail identification was based on morphological features of the shell. Each snail was acclimatized for 24 hours in a 50-ml capacity container before being exposed to strong artificial light. The 150 snails collected per month were grouped into 5 batches (n=30/batch) with each batch receiving different number of light exposures. Emerging cercariae were described and characterized using photo-referencing and standardized keys. All statistical tests were performed at p<0.05 level of significance using SPSS ver. 20.ResultsThe total cercarial shedding rate of the snails studied, as a measure of the infected snails, was found to be 35.6% and was positively associated with the length of the snail shell [OR = 1.809; 95% CI: 1.471-2.225; p<0.001], but not with the weight [OR = 0.003; 95% CI: 0.00-0.275; p=0.012] and width of the shell [OR = 0.937; 95% CI: 0.672-1.305]. The rates varied from 29.3% to 38.0% based on the frequency of 6-hour light exposure. Appearance of encysted forms increased with increasing number of light exposures [OR = 10.27, 95% CI: 3.04-34.76, p<0.001]. Three distinct cercariae were identified, namely, echinostome, longifurcate-pharyngeate distome cercariae (Strigea cercariae), and the virgulate xiphidiocercaria, with 26.4%, 2.27%, and 0.67% infection monitored by cercarial emergence, respectively.ConclusionLocal lymnaeid snails were infected with a single type of trematode larvae and coinfection with multiple larvae was rare but was encountered.

Project description:BackgroundNeorickettsia are obligate intracellular bacterial endosymbionts of digenean parasites present in all lifestages of digeneans. Quantitative information on the transmission of neorickettsial endosymbionts throughout the complex life cycles of digeneans is lacking. This study quantified the transmission of Neorickettsia during the asexual reproductive phase of a digenean parasite, Plagiorchis elegans, developing within naturally parasitized lymnaeid pond snails.MethodsLymnaea stagnalis snails were collected from 3 ponds in Nelson County, North Dakota and screened for the presence of digenean cercariae. Cercariae were identified to species by PCR and sequencing of the 28S rRNA gene. Neorickettsia infections were initially detected using nested PCR and sequencing of a partial 16S rRNA gene of pooled cercariae shed from each parasitized snail. Fifty to 100 single cercariae or sporocysts were isolated from each of six parasitized snails and tested for the presence of Neorickettsia using nested PCR to estimate the efficiency at which Neorickettsia were transmitted to cercariae during asexual development of the digenean.ResultsA total of 616 L. stagnalis were collected and 240 (39%) shed digenean cercariae. Of these, 18 (8%) were Neorickettsia-positive. Six Neorickettsia infections were selected to determine the transmission efficiency of Neorickettsia from mother to daughter sporocyst and from daughter sporocyst to cercaria. The prevalence of neorickettsiae in cercariae varied from 11 to 91%. The prevalence of neorickettsiae in sporocysts from one snail was 100%.ConclusionPrevalence of Neorickettsia infection in cercariae of Plagiorchis elegans was variable and never reached 100%. Reasons for this are speculative, however, the low prevalence of Neorickettsia observed in some of our samples (11 to 52%) differs from the high prevalence of other, related bacterial endosymbionts, e.g. Wolbachia in Wolbachia-dependent filariid nematodes, where the prevalence among progeny is universally 100%. This suggests that, unlike the Wolbachia-filaria relationship, the Neorickettsia-digenean relationship is not obligatory mutualism. Our study represents the first quantitative estimate of the Neorickettsia transmission through the asexual phase of the digenean life cycle.

Dataset Information

Morphological and molecular characterization of lymnaeid snails and their potential role in transmission of Fasciola spp. in Vietnam.

Publications

Morphological and molecular characterization of lymnaeid snails and their potential role in transmission of Fasciola spp. in Vietnam.

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