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

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.

Assessing the efficacy of albendazole against hookworm in Vietnam using quantitative PCR and sodium nitrate flotation

“…Samples were found to be embryonated, and therefore a previously-derived Ct-to-EPG conversion formula for embryonated N . americanus eggs was used (EPG = 10 (Ct-32.657)/-3.878 ) [ 32 ]. The equation was derived as follows: a serial dilution of known quantities of N .…”

“…The equation was derived as follows: a serial dilution of known quantities of N . americanus eggs were seeded into parasite-free faeces and incubated at 28°C for 5 days to allow for embryonation of eggs to occur [ 32 ]. A standard curve of Ct versus EPG values was then generated, following the same procedures published previously for unembryonated eggs [ 30 ].…”

“…Samples with the highest infection intensity (the lowest Ct values) were purposefully selected. Samples were found to be embryonated, and therefore a previously-derived Ct-to-EPG conversion formula for embryonated N. americanus eggs was used (EPG = 10 (Ct-32.657)/-3.878 ) [32]. The equation was derived as follows: a serial dilution of known quantities of N. americanus eggs were seeded into parasite-free faeces and incubated at 28˚C for 5 days to allow for embryonation of eggs to occur [32].…”

“…Samples were found to be embryonated, and therefore a previously-derived Ct-to-EPG conversion formula for embryonated N. americanus eggs was used (EPG = 10 (Ct-32.657)/-3.878 ) [32]. The equation was derived as follows: a serial dilution of known quantities of N. americanus eggs were seeded into parasite-free faeces and incubated at 28˚C for 5 days to allow for embryonation of eggs to occur [32]. A standard curve of Ct versus EPG values was then generated, following the same procedures published previously for unembryonated eggs [30].…”

Advantages and limitations of microscopy and molecular detections for diagnosis of soil-transmitted helminths: An overview

“…Standardised validation and assessment of infection intensity using qPCR are also required as DNA concentrations are commonly calculated based on individual standard curves. Different standard curves are used as quantitative measures of infection intensity ( Le B et al ., 2022 ; Papaiakovou et al ., 2018 ).…”