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.
Highlights
Schistosomiasis has been a public health problem in Brazil for decades
Snails of the genus Biomphalaria serve as intermediate hosts of the S. mansoni
polymerase chain reaction (PCR)-based diagnostic methods have been successfully applied in a few endemic areas of schistosomiasis in Brazil, they are not still widely used due to the highly technical requirements making them unviable for routine application in field conditions
Summary
Schistosomiasis has been a public health problem in Brazil for decades. Around 1.8 million people, mostly in the coastal states of Brazil, are thought to be infected with Schistosoma mansoni and 25 million living at risk of contracting the disease in America [1]. Parasitological or immunological tests are not effective for detecting S. mansoni infection in low prevalence areas polymerase chain reaction (PCR)-based diagnostic methods have been successfully developed and applied in endemic areas of schistosomiasis in Brazil [3,4,5,6,7]. They are not widely used in low-income countries due to the highly technical requirements and need for skilled personnel, making them unviable for routine application in field conditions. The present work aimed to assess the utility of our previously described SmMITLAMP assay for S. mansoni detection in human stool and snail samples in a low-transmission area of schistosomiasis in the municipality of Umbuzeiro, Paraıba State, Northeast Region of Brazil
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