Using quantitative PCR to identify opportunities to strengthen soil-transmitted helminth control in Solomon Islands: A cross-sectional epidemiological survey

PLoS Negl Trop Dis. 2022 May 23;16(5):e0010350. doi: 10.1371/journal.pntd.0010350. eCollection 2022 May.

Abstract

Background: The Kato-Katz microscopy technique is the global standard for assessment of soil-transmitted helminth (STH) burden. However, major limitations include its poor sensitivity, requirement for rapid sample processing, and inability to differentiate hookworm species nor detect Strongyloides spp. infections. We assessed the prevalence and intensity of STH species in Solomon Islands by conducting a province-wide survey using quantitative PCR (qPCR) for diagnosis, which can provide much better characterisation of STH burden than microscopy.

Methodology/principal findings: We conducted a cross-sectional survey in 18 villages in Western Province to detect infections with six STH species and quantify intensity with three. We used linear mixed model regression to identify potential water, sanitation, and hygiene (WASH) and environmental risk factors for infection. We collected stool specimens from 830 village residents. Overall STH prevalence was 63.3% (range 27.5 to 91.5% across villages), led by Necator americanus (54.5% [range 17.5-89.4%]), followed by Ancylostoma ceylanicum (15.5% [range 2.8-45.8%]), Trichuris trichiura (9.1% [range 0-79.2%]), and Strongyloides spp. (3.2% [range 0-29.2%]). Most infections were of light intensity for N. americanus (85.7%) and T. trichiura (90.7%). Owning a household latrine was associated with a lower risk of N. americanus infection (AOR 0.41, 95% CI 0.24-0.68) while greater precipitation was linked to more common T. trichiura infection (AOR 1.14, 95% CI 1.04-1.25).

Conclusion/significance: In this first large-scale population survey of STH in the Pacific using qPCR, we found evidence that ivermectin should be incorporated into STH control programmes because of the presence of T. trichiura and Strongyloides spp., both of which are poorly responsive to albendazole. Furthermore, One Health strategies are needed for improved A. ceylanicum and Strongyloides spp. control, WASH access and use should be improved to complement deworming programmes, and control efforts should ideally be expanded to entire communities.

Trial registration: ClinicalTrials.gov Australian and New Zealand Clinical Trials Registry ACTRN12618001086257.

MeSH terms

  • Animals
  • Cross-Sectional Studies
  • Environmental Monitoring / methods
  • Feces / parasitology
  • Helminthiasis* / epidemiology
  • Helminthiasis* / prevention & control
  • Helminthiasis* / transmission
  • Helminths* / genetics
  • Helminths* / isolation & purification
  • Melanesia / epidemiology
  • Prevalence
  • Real-Time Polymerase Chain Reaction
  • Risk Factors
  • Soil* / parasitology
  • Water / parasitology

Substances

  • Soil
  • Water

Associated data

  • ANZCTR/ACTRN12618001086257

Grants and funding

Fieldwork for this research was funded by a Centres of Research Excellence Grant from the National Health and Medical Research Council of Australia (NHMRC) (GNT1153727). https://www.nhmrc.gov.au/ The Regimens of Ivermectin for Scabies Elimination (RISE) trial, in which this study was embedded, is funded by the NHMRC (GNT1127297). https://www.nhmrc.gov.au/ BL is supported by the Australian Government Research Training Program Scholarship. https://www.dese.gov.au/ JK and LR are supported by fellowships from the NHMRC. https://www.nhmrc.gov.au/ AS is supported by a Viertel Senior Medical Research Fellowship and an NHMRC Investigator Grant. http://viertel.org.au/https://www.nhmrc.gov.au/ RT is supported by the Australian Research Council Future Fellowship. https://www.arc.gov.au/ The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.