Abstract

BackgroundSchistosomiasis a neglected tropical disease endemic in Brazil. It is caused by the trematode Schistosoma mansoni, which is transmitted by snails of the genus Biomphalaria. Among measures used to control and eliminate schistosomiasis, accurate mapping and monitoring of snail breeding sites are recommended. Despite the limitations of parasitological methods, they are still used to identify infected snails. Loop-mediated isothermal amplification (LAMP) is a sensitive, rapid, and cost-effective diagnostic method for the identification of infected snails. In the work reported here, we aimed to validate the use of LAMP for the detection of S. mansoni in snails of the genus Biomphalaria.MethodsSnails were collected in five municipalities of the Mucuri Valley and Jequitinhonha Valley regions in the state of Minas Gerais, Brazil. Snails were pooled according to collection site and then squeezed for the detection of S. mansoni and other trematode larvae. Pooled snails were subjected to pepsin digestion and DNA extraction. Molecular assays were performed for species-specific identification and characterization of the samples. A previously described LAMP assay was adapted, evaluated, and validated using laboratory and field samples.ResultsUsing the parasitological method described here, S. mansoni cercariae were detected in snails from two collection sites, and cercariae of the family Spirorchiidae were found in snails from one site. The snails were identified by polymerase chain reaction (PCR)–restriction fragment length polymorphism (RFLP). Biomphalaria glabrata, the main snail host of S. mansoni in Brazil, was detected in 72.2% of the collection sites. Biomphalaria kuhniana, which is resistant to S. mansoni infection, was found in the remaining sites. Multiplex, low stringency (LS), and conventional PCR allowed the detection of positive snails in four additional sites. Trematodes belonging to the families Strigeidae and Echinostomatidae were detected by multiplex PCR in two sites. The LAMP assay was effective in detecting the presence of S. mansoni infection in laboratory (7 days post-infection) and field samples with no cross-reactivity for other trematodes. When compared to LS and conventional PCR, LAMP showed 100% specificity, 85.7% sensitivity, and a κ index of 0.88.ConclusionsOur findings suggest that LAMP is a good alternative method for the detection and monitoring of transmission foci of S. mansoni, as it was three times as effective as the parasitological examination used here for the detection of infection, and is more directly applicable in the field than other molecular techniques.Graphical abstract

Highlights

  • Schistosomiasis a neglected tropical disease endemic in Brazil

  • Our findings suggest that Loop-mediated isothermal amplification (LAMP) is a good alternative method for the detection and monitoring of transmission foci of S. mansoni, as it was three times as effective as the parasitological examination used here for the detection of infection, and is more directly applicable in the field than other molecular techniques

  • Parasitological examination and morphological identification of trematode larvae The snails were separated into pools in the Lobato Paraense Mollusk Room (LPMR) at the René Rachou Institute–Oswaldo Cruz Foundation (Fiocruz) Minas according to their collection site and subjected to a shell-crushing/ squeezing method for the detection of their natural infection with S. mansoni or other trematodes

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Summary

Introduction

Schistosomiasis a neglected tropical disease endemic in Brazil It is caused by the trematode Schistosoma mansoni, which is transmitted by snails of the genus Biomphalaria. Schistosomiasis is a parasitic disease that affects nearly 240 million people in the world. It is closely associated with poor sanitation and poverty, as these lead people to use contaminated water for domestic use and leisure [1]. In Latin America, approximately 7.1 million people are infected with the etiological agent, Schistosoma mansoni, and 95% of them live in Brazil [2], where the northeastern and southeastern regions are the most affected [3]. Knowledge regarding the geographic distribution of Biomphalaria snails in Brazil is being progressively updated, and demonstrates that these intermediate host species are spreading to new locations [3]

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