Molecular approaches for the detection of Schistosoma mansoni: possible applications in the detection of snail infection, monitoring of transmission sites, and diagnosis of human infection

Abstract

The detection of specific DNA sequences by polymerase chain reaction (PCR) Key words: polymerase chain reaction -molecular diagnosis -schistosomiasis -transmission -snail -Schistosoma Schistosomiasis is a disease transmitted by fresh water snails. It affects more than 200 million people worldwide and is endemic in 74 countries, with more than 80% of infected persons living in Africa. In Brazil, Schistosoma mansoni is the only causative species of schistosomiasis, and there are three species of intermediate hosts: Biomphalaria glabrata, B. straminea, and B. tenagophila. Adult S. mansoni live in the bloodstream. Their eggs pass out of the host with the faeces. In contact with water, free-swimming miracidia emerge from the egg and penetrate the soft tissues of the snail host. Within the snails, miracidia immediately differentiate into sporocysts and, as they migrate through the snail tissues, give rise to cercariae. Cercariae are shed from the snails and are infective to humans by direct penetration of the skin. Thus, molecular approaches can be used to detect DNA of different life cycle stages of S. mansoni by analyzing different biological samples: feces, snail tissues, and infested water bodies, resulting in diagnosis of vertebrate and invertebrate host infections, and identification of transmission sites.The detection of specific DNA sequences by polymerase chain reaction (PCR) has proved extremely valuable for the analysis of genetic disorders and the diagnosis of a variety of infectious disease pathogens (Leal et al.

Advances in the Diagnosis of Human Schistosomiasis

“…Also, there are reports of focal and low-frequency cercarial shedding in areas of high Schistosoma transmission (313). Furthermore, the labor-intensive nature of these procedures, including the collection and maintenance of snails and the associated costs, are both major hindrances in their application (314).…”

“…Amplification of different species-specific schistosome gene segments in snails, including the 18S rDNA gene of S. mansoni and the DraI 121-bp repeat sequence of S. haematobium, has been tested successfully and applied in community studies on a large scale (310,312,319,320). Modified PCR methods, including multiplex and nested PCRs, have also been used successfully for the identification of infected snails (314)(315)(316)(320)(321)(322).…”

Detection of Opisthorchis viverrini in infected bithynid snails by real-time fluorescence resonance energy transfer PCR-based method and melting curve analysis

“…1 Amplification plot of fluorescence (y-axis) vs cycle numbers (x-axis) show the analytical sensitivity of the realtime PCR for detecting Opisthorchis viverrini plasmid DNA. a O. viverrini plasmid 10 11 copies/reaction; b O. viverrini plasmid 10 10 copies/reaction; c O. viverrini plasmid 10 9 copies/reaction; d O. viverrini plasmid 10 8 copies/reaction; e O. viverrini plasmid 10 7 copies/reaction; f O. viverrini plasmid 10 6 copies/reaction; g O. viverrini plasmid 10 5 copies/reaction; h O. viverrini plasmid 10 4 copies/reaction; i O. viverrini plasmid 10 3 copies/reaction; j O. viverrini plasmid 10 2 copies/reaction; k distilled water (Abath et al 2006;Abbasi et al 2007), Fasciola hepatica (Cucher et al 2006), Echinostoma caproni (Hertel et al 2003), O. viverrini (Maleewong et al 2003), and Clonorchis sinensis (Müller et al 2007). Recently, the real-time FRET PCR-based method has been successfully used for the detection of parasites, e.g., detection of Wuchereria bancrofti (Lulitanond et al 2004), Brugia malayi (Thanchomnang et al 2008), Toxoplasma gondii (Brenier-Pinchart et al 2007, and Plasmodium falciparum (Ojurongbe et al 2007).…”

Medicinal plants and their bioactive constituents: A review of bioactivity against Schistosoma mansoni

“…Within the snails, miracidia immediately differentiate into sporocysts and, as they migrate through the snail tissues, give rise to cercariae. Cercariae are shed from the snails and are infective to humans by direct penetration of the skin (Abath et al, 2006) (Figure 1). …”