A field survey using LAMP assay for detection of Schistosoma mansoni in a low-transmission area of schistosomiasis in Umbuzeiro, Brazil: Assessment in human and snail samples

Abstract

BackgroundIn Brazil, schistosomiasis is a parasitic disease of public health relevance, mainly in poor areas where Schistosoma mansoni is the only human species encountered and Biomphalaria straminea is one of the intermediate host snails. A nested-PCR based on a specific mitochondrial S. mansoni minisatellite DNA region has been successfully developed and applied as a reference method in Brazil for S. mansoni detection, mainly in host snails for epidemiological studies. The amplification efficiency of LAMP is known to be higher than PCR. The present work aimed to assess the utility of our previously described SmMIT-LAMP assay for S. mansoni detection in human stool and snail samples in a low-transmission area of schistosomiasis in the municipality of Umbuzeiro, Paraíba State, Northeast Region of Brazil.Methodology/Principal findingsA total of 427 human stool samples were collected during June-July 2016 in the municipality of Umbuzeiro and an overall prevalence of 3.04% (13/427) resulted positive by duplicate Kato-Katz thick smear. A total of 1,175 snails identified as Biomphalaria straminea were collected from 14 breeding sites along the Paraíba riverbank and distributed in 46 pools. DNA from human stool samples and pooled snails was extracted using the phenol/chloroform method. When performing the SmMIT-LAMP assay a total of 49/162 (30.24%) stool samples resulted positive, including 12/13 (92.31%) that were Kato-Katz positive and 37/149 (24.83%) previously Kato-Katz negative. By nested-PCR, only 1/46 pooled DNA snail samples was positive. By SmMIT-LAMP assay, the same sample also resulted positive and an additional one was positive from a different breeding site. Data of human and snail surveys were used to build risk maps of schistosomiasis incidence using kernel density analysis.Conclusions/SignificanceThis is the first study in which a LAMP assay was evaluated in both human stool and snail samples from a low-transmission schistosomiasis-endemic area. Our SmMIT-LAMP proved to be much more efficient in detection of S. mansoni in comparison to the 'gold standard' Kato-Katz method in human stool samples and the reference molecular nested-PCR in snails. The SmMIT-LAMP has demonstrated to be a useful molecular tool to identify potential foci of transmission in order to build risk maps of schistosomiasis.

Comparison of Reverse Transcription Loop-Mediated Isothermal Amplification Method with SYBR Green Real-Time RT-PCR and Direct Fluorescent Antibody Test for Diagnosis of Rabies

“…The RT-LAMP assay was initially developed by Notomi et al (13) and was recently recommended for the diagnosis of diseases at the fields (20,21). In the present study, we applied and evaluated RT-LAMP assay as a fast, sensitive, specific, and cost-effective method for rapid detection of rabies virus in animal brain samples.…”

Loop-Mediated Isothermal Amplification as Point-of-Care Diagnosis for Neglected Parasitic Infections

“…The authors modified the protocol for obtaining this limit, increasing incubation time from 60 to 120 minutes; this improved analytical sensitivity from 1 fg to 0.01 fg and increasing incubation time did not affect test specificity. Using this set of primers which had already been tested in urine [152], faeces [158] and snails [155], the research group improved the protocol, transforming it into a cold maintenance dry format, suitable for potentially manufacturing as a kit for ready-to-use for schistosomiasis diagnosis [150]. Price et al [151] amplified the Sm1-7 sequence for evaluating the effect of extraction on LAMP performance, finding greater sensitivity and specificity when samples were extracted with a LAMP-Qiagen kit (100% sensitivity: 96-100% 95% CI; 100% specificity: 59-100% 95% CI), compared to using PCR-Qiagen, PCR_LAMP-PURE, LAMP_LAMP_PURE kits.…”

DNA Diagnostics for Schistosomiasis Control

“…Furthermore, a LAMP assay has been used in the sensitive detection of early pre-patent schistosome infection in an animal model [ 89 ]. In a recent field survey to detect S. mansoni infection in a low-transmission area, a LAMP assay was successfully applied in both snail and human stool samples and the study emphasized the potential application of this molecular approach for the identification of transmission foci and for building risk maps in support of control programs [ 48 ]. Furthermore, the LAMP method was successfully used recently in China for surveillance, including in snail surveys, indicating its usefulness, and applicability as a rapid screening and environmental risk assessment tool to identify areas suitable for targeted intervention [ 12 ].…”

“…The application of multiplex qPCR assays have the additional advantage of identifying both snail and infecting schistosome species, another helpful consideration for successful schistosome and snail control programs [ 136 ]. Furthermore, molecular methods are of considerable help in developing transmission risk maps prior to the instigation of control efforts [ 48 , 135 ].…”