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Journal ArticleDOI

Detection of Schistosoma mansoni in Biomphalaria using nested PCR.

01 Jun 1997-Journal of Parasitology (J Parasitol)-Vol. 83, Iss: 3, pp 387-394
TL;DR: A nested polymerase chain reaction (PCR) protocol was developed for detecting the presence of Schistosoma mansoni sporocysts in intermediate host snails of the genus Biomphalaria and has utility in determining if snails in endemic areas bear prepatent or inactive infections and in assessing the degree of compatibility between local snail and schistosome populations.
Abstract: A nested polymerase chain reaction (PCR) protocol was developed for detecting the presence of Schistosoma mansoni sporocysts in intermediate host snails of the genus Biomphalaria. To accomplish this, rDNA genes encoding the 18S rRNA of S. mansoni and Biomphalaria alexandrina from Egypt were sequenced, as were 18S-encoding genes of the 13-16-R1 and Salvador strains of Biomphalaria glabrata. Based on a comparison of host and parasite sequences, a nested set of PCR primers was designed to allow specific amplification of portions of S. mansoni 18S rDNA. These primers allowed detection of as little as 10 fg of S. mansoni DNA diluted in 100 ng of snail DNA and did not allow amplification of snail 18S sequences. Using nested PCR, the presence of a single S. mansoni sporocyst within an adult snail could be detected at 1 day postexposure. In DNA samples extracted from each of 74 snails of the M-line strain of B. glabrata exposed to from 1 to 10 S. mansoni miracidia for intervals ranging from 1 to 44 days, use of the outside primer pair alone detected the parasite's presence in 51% of the snails, whereas the sequential use of outside and nested primer pairs detected parasites in 92% of the snails. This approach has utility in determining if snails in endemic areas bear prepatent or inactive infections and in assessing the degree of compatibility between local snail and schistosome populations. It will also facilitate studies of resistance of snails to infection.
Citations
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Journal ArticleDOI
TL;DR: Careful and rigorous validation of these assays and their cost-effectiveness will be needed, however, prior to their adoption in support of policy decisions for national public health programs aimed at the control and elimination of schistosomiasis.
Abstract: Schistosomiasis is a major neglected tropical disease that afflicts more than 240 million people, including many children and young adults, in the tropics and subtropics. The disease is characterized by chronic infections with significant residual morbidity and is of considerable public health importance, with substantial socioeconomic impacts on impoverished communities. Morbidity reduction and eventual elimination through integrated intervention measures are the focuses of current schistosomiasis control programs. Precise diagnosis of schistosome infections, in both mammalian and snail intermediate hosts, will play a pivotal role in achieving these goals. Nevertheless, despite extensive efforts over several decades, the search for sensitive and specific diagnostics for schistosomiasis is ongoing. Here we review the area, paying attention to earlier approaches but emphasizing recent developments in the search for new diagnostics for schistosomiasis with practical applications in the research laboratory, the clinic, and the field. Careful and rigorous validation of these assays and their cost-effectiveness will be needed, however, prior to their adoption in support of policy decisions for national public health programs aimed at the control and elimination of schistosomiasis.

221 citations

Journal ArticleDOI
TL;DR: The efficacy of environmental management and the use of molluscicides and biological agents to control snail populations are reviewed and the development of diagnostic tests, based on the detection of parasite antigens or specific parasite DNA sequences in snail tissues, are described.

117 citations

Journal ArticleDOI
TL;DR: In the first month of infection, the PCR method was more sensitive than using the egg-count method in all infected groups especially in the light infections and was also successfully used in monitoring a therapeutic study.
Abstract: Opisthorchis viverrini infection is an endemic disease that causes a serious public health problem in southeast Asia, especially in northeast Thailand, We have developed a PCR method using a pair of primers named OV-6F/OV-6R for detecting O. viverrini eggs in stool samples and compared it with Stoll's egg-count method. The primers were designed based on the pOV-A6 specific DNA probe sequence which gave a 330 base pair product. The PCR method can detect a single egg in artificially inoculated faeces or as little as 2 × 10 -17 ng of O. viverrini genomic DNA. The method gave 100% sensitivity in all hamster groups except in animals exposed to the lowest intensity of infection (1 metacercaria/hamster). In the first month of infection, the PCR method was more sensitive than using the egg-count method in all infected groups especially in the light infections. 'l'he PCR method was also successfully used in monitoring a therapeutic study. Since the PCR method showed no cross-reaction with Heterophyid flukes, it can be useful for specific identification of O. viverrini eggs in stool samples without the risk of false positives. It also has great potential for application in clinical epidemiological studies.

90 citations


Cites background or methods from "Detection of Schistosoma mansoni in..."

  • ...PCRbased detection of the helminthic infections usually utilizes either a rRNA gene, specific or highly repetitive sequences (Hanelt et al. 1997; Dinkel et al. 1998; Hamburger et al. 1998)....

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  • ...Our method is more sensitive (2¬10w"( ng) than those reported for other helminths (Mathis, Deplazes & Eckert, 1996; Fischer et al. 1997; Hanelt et al. 1997; Dinkel et al. 1998; Hamburger et al. 1998)....

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Journal ArticleDOI
TL;DR: A polymerase chain reaction (PCR) assay, previously shown by us to be very sensitive for detecting cercariae in water, is adapted for the sensitive detection of Schistosoma mansoni DNA in infected snails from early prepatency, providing the potential for large-scale determination of prepatent infection prevalence in snails.
Abstract: In the present study, we adapted a polymerase chain reaction (PCR) assay, previously shown by us to be very sensitive for detecting cercariae in water, for the sensitive detection of Schistosoma mansoni DNA in infected snails from early prepatency. Polymerase chain reaction primers were designed based on the 121-basepair highly repeated sequence we previously identified in the genome of S. mansoni. The DNA was prepared from the snails by a simple alkaline extraction procedure, and the PCR assay enabled a clear differentiation between infected and normal snails. Infected snails were detected as early as one day after penetration of a single miracidium. The high sensitivity of the test enabled identification of a single infected snail even when its DNA was pooled with material from up to 99 uninfected snails, thus demonstrating the possibility of mass diagnosis in pools of snails. The assay has the potential for large-scale determination of prepatent infection prevalence in snails, thus offering new possibilities for the evaluation of schistosomiasis transmission and for schistosomiasis control, as discussed.

82 citations

Journal ArticleDOI
TL;DR: EDNA provides a promising tool to substantially improve the environmental surveillance of S. mansoni in freshwater samples by using aquatic eDNA, and could become an essential future component of the schistosomiasis control tool box needed to achieve the goal of elimination.
Abstract: Schistosomiasis is a water-based, infectious disease with high morbidity and significant economic burdens affecting >250 million people globally. Disease control has, with notable success, for decades focused on drug treatment of infected human populations, but a recent paradigm shift now entails moving from control to elimination. To achieve this ambitious goal, more sensitive diagnostic tools are needed to monitor progress toward transmission interruption in the environment, especially in low-intensity infection areas. We report on the development of an environmental DNA (eDNA)-based tool to efficiently detect DNA traces of the parasite Schistosoma mansoni directly in the aquatic environment, where the nonhuman part of the parasite life cycle occurs. This is a report of the successful detection of S. mansoni in freshwater samples by using aquatic eDNA. True eDNA was detected in as few as 10 cercariae per liter of water in laboratory experiments. The field applicability of the method was tested at known transmission sites in Kenya, where comparison of schistosome detection by conventional snail surveys (snail collection and cercariae shedding) with eDNA (water samples) showed 71% agreement between the methods. The eDNA method furthermore detected schistosome presence at two additional sites where snail shedding failed, demonstrating a higher sensitivity of eDNA sampling. We conclude that eDNA provides a promising tool to substantially improve the environmental surveillance of S. mansoni. Given the proper method and guideline development, eDNA could become an essential future component of the schistosomiasis control tool box needed to achieve the goal of elimination.

81 citations


Cites background from "Detection of Schistosoma mansoni in..."

  • ...Even though introduction of DNA techniques for molecular detection of parasite infections in snails recently has revitalized traditional snail-monitoring methods (14, 15), extensive snail surveys are still needed to confirm parasite presence....

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