Detection of Schistosoma japonicum and Oncomelania hupensis quadrasi environmental DNA and its potential utility to schistosomiasis japonica surveillance in the Philippines

PLoS One. 2019 Nov 20;14(11):e0224617. doi: 10.1371/journal.pone.0224617. eCollection 2019.

Abstract

In recent years, the prevalence and infection intensity of Schistosoma japonicum in endemic areas of the Philippines have significantly decreased due to yearly population-based treatment strategies, yet transmission rates remain high and uninterrupted. An important indicator of active disease transmission is the presence of Schistosoma japonicum and its snail intermediate host Oncomelania hupensis quadrasi in freshwater habitats. In this study, we sought to apply a species-specific real-time PCR (qPCR) assay for the detection of S. japonicum and O. hupensis quadrasi in freshwater samples using environmental DNA approach that can complement the commonly utilized malacological survey in determining potential transmission foci in order to have a more effective snail surveillance strategy for schistosomiasis japonica in endemic areas. The newly developed assay was specific to S. japonicum and O. hupensis quadrasi with no amplification detected against non-target trematode Fasciola spp. and snails such as Lymnaea spp., Pomacea canaliculata, and Melanoides spp. that typically co-exist in the same environment. The assay effectiveness was determined using 19 environmental water samples collected from Northern Samar (N = 5 sites), Leyte (N = 11 sites) and Compostela Valley (N = 3 sites) and compared to malacological survey for determining O. hupensis quadrasi snail colonies and snail crushing to visualize S. japonicum cercariae. TaqMan qPCR targeting a short fragment of the cytochrome c oxidase subunit 1 (cox1) gene was positive for S. japonicum in 9 sites, for O. hupensis quadrasi in 9 sites, and for both S. japonicum and O. hupensis quadrasi in 5 sampling sites. Moreover, it was able to detect O. hupensis quadrasi in 3 out of 12 sites found negative and 6 out of 7 sites found positive through malacological survey, and in 4 of the 5 snail sites positive for snails with cercariae. Overall, this method can complement malacological surveys for monitoring of schistosomes in endemic areas of the Philippines, especially those with high risk of human infection.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Cercaria / genetics
  • DNA, Environmental / genetics
  • DNA, Environmental / isolation & purification*
  • Disease Vectors
  • Epidemiological Monitoring*
  • Humans
  • Philippines / epidemiology
  • Schistosoma japonicum / genetics
  • Schistosoma japonicum / isolation & purification*
  • Schistosomiasis japonica / epidemiology
  • Schistosomiasis japonica / parasitology
  • Schistosomiasis japonica / prevention & control*
  • Schistosomiasis japonica / transmission
  • Snails / genetics*
  • Snails / parasitology
  • Species Specificity

Substances

  • DNA, Environmental

Grants and funding

IKCF received grant from the Department of Science and Technology – Philippine Council for Industry, Energy and Emerging Technology Research and Development (Grant No. PCIEERD-BIO-17-02) in partnership with the University of the Philippines Diliman-Natural Sciences Research Institute and Institute of Biology, College of Science, http://pcieerd.dost.gov.ph/. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.