The Right Tool for the Job: Detection of Soil-Transmitted Helminths in Areas Co-endemic for Other Helminths

Background

Due to the recent increased use of the McMaster (MM) fecal egg counting method for assessing benzimidazole drug efficacy for treating soil-transmitted helminth (STH) infections, the aim of the current study was to determine the operational value of including the MM method alongside the Kato-Katz (KK) fecal thick smear to increase the diagnostic sensitivity when STHs are co-endemic with trematode helminths (e.g., Schistosoma mansoni).

Methods

A cross-sectional study was conducted in school-aged children aged 4-18 years in the northeastern region of the State of Minas Gerais (Brazil), where Necator americanus, Ascaris lumbricoides, Trichuris trichiura, and S. mansoni are co-endemic. One fecal sample from each participant was collected and transported to the field laboratory for analysis. Coprological diagnosis was performed on each fecal sample by three different methods: Formalin-Ether Sedimentation (FES), KK and the MM technique. The diagnostic sensitivity and negative predictive value (NPV) of each technique was calculated using the combination of all three techniques as the composite standard. In order to determine the agreement between the three techniques Fleiss´ kappa was used. Both the Cure Rate (CR) and the Fecal Egg Count Reduction (FECR) were calculated using the two quantification techniques (i.e., the MM and KK).

Results

Fecal samples from 1260 children were analyzed. The KK had higher diagnostic sensitivity than the MM for the detection of both A. lumbricoides (KK 97.3%, MM 69.5%) and hookworm (KK 95.1%, MM 80.8%). The CR of a single dose of mebendazole varied significantly between the KK and MM for both A. lumbricoides (p = 0.016) and hookworm (p = 0.000), with lower rates obtained with the KK. On the other hand, the FECR was very similar between both techniques for both A. lumbricoides and hookworm.

Conclusion

The MM did not add any diagnostic value over the KK in areas where both STHs and trematodes were co-endemic. The lower sensitivity of the MM would have an important impact on the administration of selective school-based treatment in this area since if only the MM were used, 36 (13.9%) children diagnosed with A. lumbricoides would have gone untreated.     

The Epidemiology of Soil-Transmitted Helminths in Bihar State,India

Background

Soil-transmitted helminths (STHs) infect over a billion individuals worldwide. In India, 241 million children are estimated to need deworming to avert the negative consequences STH infections can have on child health and development. In February-April 2011, 17 million children in Bihar State were dewormed during a government-led school-based deworming campaign. Prior to programme implementation, a study was conducted to assess STH prevalence in the school-age population to direct the programme. The study also investigated risk factors for STH infections, including caste, literacy, and defecation and hygiene practices, in order to inform the development of complementary interventions.

Methods

A cross-sectional survey was conducted among children in 20 schools in Bihar. In addition to providing stool samples for identification of STH infections, children completed a short questionnaire detailing their usual defecation and hand-hygiene practices. Risk factors for STH infections were explored.

Results

In January-February 2011, 1279 school children aged four to seventeen provided stool samples and 1157 children also completed the questionnaire. Overall, 68% of children (10-86% across schools) were infected with one or more soil-transmitted helminth species. The prevalence of ascariasis, hookworm and trichuriasis was 52%, 42% and 5% respectively. The majority of children (95%) practiced open defecation and reported most frequently cleansing hands with soil (61%). Increasing age, lack of maternal literacy and certain castes were independently associated with hookworm infection. Absence of a hand-washing station at the schools was also independently associated with A. lumbricoides infection.

Conclusions

STH prevalence in Bihar is high, and justifies mass deworming in school-aged children. Open defecation is common-place and hands are often cleansed using soil. The findings reported here can be used to help direct messaging appropriate to mothers with low levels of literacy and emphasise the importance of water and sanitation in the control of helminths and other diseases.     

How Long Can Stool Samples Be Fixed for an Accurate Diagnosis of Soil-Transmitted Helminth Infection Using Mini-FLOTAC?

Background

Kato-Katz is a widely used method for the diagnosis of soil-transmitted helminth infection. Fecal samples cannot be preserved, and hence, should be processed on the day of collection and examined under a microscope within 60 min of slide preparation. Mini-FLOTAC is a technique that allows examining fixed fecal samples. We assessed the performance of Mini-FLOTAC using formalin-fixed stool samples compared to Kato-Katz and determined the dynamics of prevalence and intensity estimates of soil-transmitted helminth infection over a 31-day time period.

Methodology

The study was carried out in late 2013 on Pemba Island, Tanzania. Forty-one children were enrolled and stool samples were subjected on the day of collection to a single Kato-Katz thick smear and Mini-FLOTAC examination; 12 aliquots of stool were fixed in 5% formalin and subsequently examined by Mini-FLOTAC up to 31 days after collection.

Principal Findings

The combined results from Kato-Katz and Mini-FLOTAC revealed that 100% of children were positive for Trichuris trichiura, 85% for Ascaris lumbricoides, and 54% for hookworm. Kato-Katz and Mini-FLOTAC techniques found similar prevalence estimates for A. lumbricoides (85% versus 76%), T. trichiura (98% versus 100%), and hookworm (42% versus 51%). The mean eggs per gram of stool (EPG) according to Kato-Katz and Mini-FLOTAC was 12,075 and 11,679 for A. lumbricoides, 1,074 and 1,592 for T. trichiura, and 255 and 220 for hookworm, respectively. The mean EPG from day 1 to 31 of fixation was stable for A. lumbricoides and T. trichiura, but gradually declined for hookworm, starting at day 15.

Conclusions/Significance

The findings of our study suggest that for a qualitative diagnosis of soil-transmitted helminth infection, stool samples can be fixed in 5% formalin for at least 30 days. However, for an accurate quantitative diagnosis of hookworm, we suggest a limit of 15 days of preservation. Our results have direct implication for integrating soil-transmitted helminthiasis into transmission assessment surveys for lymphatic filariasis.     

Impact of long-term treatment with ivermectin on the prevalence and intensity of soil-transmitted helminth infections

Background

Control of soil-transmitted helminth (STH) infections relies on the periodic and long-term administration of anthelmintic drugs to high-risk groups, particularly school-age children living in endemic areas. There is limited data on the effectiveness of long-term periodic anthelmintic treatment on the prevalence of STHs, particularly from operational programmes. The current study investigated the impact of 15 to 17 years of treatment with the broad-spectrum anthelmintic ivermectin, used for the control of onchocerciasis, on STH prevalence and intensity in school-age and pre-school children.

Methods and Findings

A cross-sectional study was conducted in communities that had received annual or twice-annual ivermectin treatments and geographically adjacent communities that had not received treatment in two districts of Esmeraldas Province in Ecuador. Stool samples were collected from school-age children and examined for STH infection using the Kato-Katz and formol-ether concentration methods. Samples were collected also from pre-school children and examined by the formol-ether concentration method. Data on risk factors for STH infection were collected by parental questionnaire. We sampled a total of 3,705 school-age children (6–16 years) from 31 treated and 27 non-treated communities, and 1,701 pre-school children aged 0–5 years from 18 treated and 18 non-treated communities. Among school-age children, ivermectin treatment had significant effects on the prevalence (adjusted OR =  0.06, 95% CI 0.03–0.14) and intensity of Trichuris trichiura infection (adjusted RR = 0.28, 95% CI 0.11–0.70), but appeared to have no impact on Ascaris lumbricoides or hookworm infection. Reduced prevalence and intensities of T. trichiura infection were observed among children not eligible to receive ivermectina, providing some evidence of reduced transmission of T. trichiura infection in communities receiving mass ivermectin treatments.

Conclusion

Annual and twice-annual treatments with ivermectin over a period of up to 17 years may have had a significant impact on T. trichiura infection. The present data indicate that the long-term control of onchocerciasis with ivermectin may provide additional health benefits by reducing infections with trichuriasis. The addition of a second anthelmintic drug such as albendazole may be useful for a long-term effect on A. lumbricoides infection.     

Assessment of Anthelmintic Efficacy of Mebendazole in School Children in Six Countries Where Soil-Transmitted Helminths Are Endemic

Background

Robust reference values for fecal egg count reduction (FECR) rates of the most widely used anthelmintic drugs in preventive chemotherapy (PC) programs for controlling soil-transmitted helminths (STHs; Ascaris lumbricoides, Trichuris trichiura, and hookworm) are still lacking. However, they are urgently needed to ensure detection of reduced efficacies that are predicted to occur due to growing drug pressure. Here, using a standardized methodology, we assessed the FECR rate of a single oral dose of mebendazole (MEB; 500 mg) against STHs in six trials in school children in different locations around the world. Our results are compared with those previously obtained for similarly conducted trials of a single oral dose of albendazole (ALB; 400 mg).

Methodology

The efficacy of MEB, as assessed by FECR, was determined in six trials involving 5,830 school children in Brazil, Cambodia, Cameroon, Ethiopia, United Republic of Tanzania, and Vietnam. The efficacy of MEB was compared to that of ALB as previously assessed in 8,841 school children in India and all the above-mentioned study sites, using identical methodologies.

Principal Findings

The estimated FECR rate [95% confidence interval] of MEB was highest for A. lumbricoides (97.6% [95.8; 99.5]), followed by hookworm (79.6% [71.0; 88.3]). For T. trichiura, the estimated FECR rate was 63.1% [51.6; 74.6]. Compared to MEB, ALB was significantly more efficacious against hookworm (96.2% [91.1; 100], p<0.001) and only marginally, although significantly, better against A. lumbricoides infections (99.9% [99.0; 100], p = 0.012), but equally efficacious for T. trichiura infections (64.5% [44.4; 84.7], p = 0.906).

Conclusions/Significance

A minimum FECR rate of 95% for A. lumbricoides, 70% for hookworm, and 50% for T. trichiura is expected in MEB-dependent PC programs. Lower FECR results may indicate the development of potential drug resistance.     

Soil-Transmitted Helminths and Associated Factors among Pre-School Children in Butajira Town,South-Central Ethiopia: A Community-Based Cross-Sectional Study

Background

Soil-transmitted helminths (STH) remain a major public health problem, particularly in tropical and sub-tropical regions of the world. Though infections are prevalent among all age groups, the world health organization (WHO) considers Pre-school age children (PSAC), school-aged children, and pregnant women as segments of population at high risk of STH morbidities.

Objective

This study aimed at determining the prevalence and infection intensity of STH and associated factors among PSAC in Butajira Town, south-central Ethiopia.

Methods

A community-based cross-sectional study was conducted from May to June, 2014 in Butajira Town. The PSAC were selected by systematic sampling technique and invited to participate in the present study. McMaster technique was employed for parasitological analysis of stool samples. Pearson’s Chi-square and Fisher’s exact tests were performed where appropriate to identify any association between STH infection and independent factors. Multivariate logistic regression model was fitted to identify independent predictors of STH among the PSAC. P-value less than 0.05 was considered statistically significant.

Results

A total of 377 (with 96% compliance rate) PSAC were able to provide complete data (socio-demographic information and stool sample). The study showed that 23.3% (88/377) PSAC were infected with one or more species of STH. Ascaris lumbricoides was the most prevalent STH (14.9%) followed by Trichuris trichiura (6.4%). The overall infection intensity, expressed as geometric mean for A. lumbricoides, T. trichiura, and hookworms were 229, 178, and 154 eggs per gram of stool, respectively. The multivariate logistic regression model estimated that being in the age group of 36–47 months (AOR: 2.5, 95% CI: 1.2–5.3, P = 0.016), untrimmed finger nail (AOR: 3.2, 95% CI: 1.8–5.5, P < 0.001), and not washing hands before a meal (AOR: 3.0, 95% CI: 1.7–5.4, P < 0.001) were independent predictors of STH infections among the children.

Conclusion

The present study showed that STH was a public health problem among PSAC in the study area necessitating annual deworming to control morbidities associated with STH. Besides, the existing health education program should also be strengthened to prevent re-infection.     

Patent Human Infections with the Whipworm,Trichuris trichiura,Are Not Associated with Alterations in the Faecal Microbiota

Background

The soil-transmitted helminth (STH), Trichuris trichiura colonises the human large intestine where it may modify inflammatory responses, an effect possibly mediated through alterations in the intestinal microbiota. We hypothesised that patent T. trichiura infections would be associated with altered faecal microbiota and that anthelmintic treatment would induce a microbiota resembling more closely that observed in uninfected individuals.

Materials and Methods

School children in Ecuador were screened for STH infections and allocated to 3 groups: uninfected, T. trichiura only, and mixed infections with T. trichiura and Ascaris lumbricoides. A sample of uninfected children and those with T. trichiura infections only were given anthelmintic treatment. Bacterial community profiles in faecal samples were studied by 454 pyrosequencing of 16 S rRNA genes.

Results

Microbiota analyses of faeces were done for 97 children: 30 were uninfected, 17 were infected with T. trichiura, and 50 with T. trichiura and A. lumbricoides. Post-treatment samples were analyzed for 14 children initially infected with T. trichiura alone and for 21 uninfected children. Treatment resulted in 100% cure of STH infections. Comparisons of the microbiota at different taxonomic levels showed no statistically significant differences in composition between uninfected children and those with T. trichiura infections. We observed a decreased proportional abundance of a few bacterial genera from the Clostridia class of Firmicutes and a reduced bacterial diversity among children with mixed infections compared to the other two groups, indicating a possible specific effect of A. lumbricoides infection. Anthelmintic treatment of children with T. trichiura did not alter faecal microbiota composition.

Discussion

Our data indicate that patent human infections with T. trichiura may have no effect on faecal microbiota but that A. lumbricoides colonisation might be associated with a disturbed microbiota. Our results also catalogue the microbiota of rural Ecuadorians and indicate differences with individuals from more urban industrialised societies.     

Risk Factors for Soil-Transmitted Helminth Infections during the First 3 Years of Life in the Tropics; Findings from a Birth Cohort

Background

Soil-transmitted helminths (STH) infect more than 2 billion humans worldwide, causing significant morbidity in children. There are few data on the epidemiology and risk factors for infection in pre-school children. To investigate risk factors for infection in early childhood, we analysed data prospectively collected in the ECUAVIDA birth cohort in Ecuador.

Methods and Findings

Children were recruited at birth and followed up to 3 years of age with periodic collection of stool samples that were examined microscopically for STH parasites. Data on social, demographic, and environmental risk factors were collected from the mother at time of enrolment. Associations between exposures and detection of STH infections were analysed by multivariable logistic regression. Data were analysed from 1,697 children for whom a stool sample was obtained at 3 years. 42.3% had at least one STH infection in the first 3 years of life and the most common infections were caused by A. lumbricoides (33.2% of children) and T. trichiura (21.2%). Hookworm infection was detected in 0.9% of children. Risk of STH infection was associated with factors indicative of poverty in our study population such as Afro-Ecuadorian ethnicity and low maternal educational level. Maternal STH infections during pregnancy were strong risk factors for any childhood STH infection, infections with either A. lumbricoides or T. trichiura, and early age of first STH infection. Children of mothers with moderate to high infections intensities with A. lumbricoides were most at risk.

Conclusions

Our data show high rates of infection with STH parasites during the first 3 years of life in an Ecuadorian birth cohort, an observation that was strongly associated with maternal STH infections during pregnancy. The targeted treatment of women of childbearing age, in particular before pregnancy, with anthelmintic drugs could offer a novel approach to the prevention of STH infections in pre-school children.     

Mass Administration of Ivermectin for the Elimination of Onchocerciasis Significantly Reduced and Maintained Low the Prevalence of Strongyloides stercoralis in Esmeraldas,Ecuador

Objectives

To evaluate the effect of ivermectin mass drug administration on strongyloidiasis and other soil transmitted helminthiases.

Methods

We conducted a retrospective analysis of data collected in Esmeraldas (Ecuador) during surveys conducted in areas where ivermectin was annually administered to the entire population for the control of onchocerciasis.Data from 5 surveys, conducted between 1990 (before the start of the distribution of ivermectin) and 2013 (six years after the interruption of the intervention) were analyzed. The surveys also comprised areas where ivermectin was not distributed because onchocerciasis was not endemic.Different laboratory techniques were used in the different surveys (direct fecal smear, formol-ether concentration, IFAT and IVD ELISA for Strongyloides stercoralis).

Results

In the areas where ivermectin was distributed the strongyloidiasis prevalence fell from 6.8% in 1990 to zero in 1996 and 1999. In 2013 prevalence in children was zero with stool examination and 1.3% with serology, in adult 0.7% and 2.7%.In areas not covered by ivermectin distribution the prevalence was 23.5% and 16.1% in 1996 and 1999, respectively. In 2013 the prevalence was 0.6% with fecal exam and 9.3% with serology in children and 2.3% and 17.9% in adults.Regarding other soil transmitted helminthiases: in areas where ivermectin was distributed the prevalence of T. trichiura was significantly reduced, while A. lumbricoides and hookworms were seemingly unaffected.

Conclusions

Periodic mass distribution of ivermectin had a significant impact on the prevalence of strongyloidiasis, less on trichuriasis and apparently no effect on ascariasis and hookworm infections.     

The Interaction of Deworming,Improved Sanitation,and Household Flooring with Soil-Transmitted Helminth Infection in Rural Bangladesh

Background

The combination of deworming and improved sanitation or hygiene may result in greater reductions in soil-transmitted helminth (STH) infection than any single intervention on its own. We measured STH prevalence in rural Bangladesh and assessed potential interactions among deworming, hygienic latrines, and household finished floors.

Methodology

We conducted a cross-sectional survey (n = 1,630) in 100 villages in rural Bangladesh to measure three exposures: self-reported deworming consumption in the past 6 months, access to a hygienic latrine, and household flooring material. We collected stool samples from children 1–4 years, 5–12 years, and women 15–49 years. We performed mini-FLOTAC on preserved stool samples to detect Ascaris lumbricoides, Enterobius vermicularis, hookworm, and Trichuris trichiura ova. Approximately one-third (32%) of all individuals and 40% of school-aged children had an STH infection. Less than 2% of the sample had moderate/heavy intensity infections. Deworming was associated with lower Ascaris prevalence (adjusted prevalence ratio (PR) = 0.53; 95% CI 0.40, 0.71), but there was no significant association with hookworm (PR = 0.93, 95% CI 0.60, 1.44) or Trichuris (PR = 0.90, 95% CI 0.74, 1.08). PRs for hygienic latrine access were 0.91 (95% CI 0.67,1.24), 0.73 (95% CI 0.43,1.24), and 1.03 (95% CI 0.84,1.27) for Ascaris, hookworm, and Trichuris, respectively. Finished floors were associated with lower Ascaris prevalence (PR = 0.56, 95% CI 0.32, 0.97) but not associated with hookworm (PR = 0.48 95% CI 0.16,1.45) or Trichuris (PR = 0.98, 95% CI 0.72,1.33). Across helminths and combinations of exposures, adjusted prevalence ratios for joint exposures were consistently more protective than those for individual exposures.

Conclusions

We found moderate STH prevalence in rural Bangladesh among children and women of childbearing age. This study is one of the first to examine independent and combined associations with deworming, sanitation, and hygiene. Our results suggest that coupling deworming with sanitation and flooring interventions may yield more sustained reductions in STH prevalence.     

Infection with Soil-Transmitted Helminths Is Associated with Increased Insulin Sensitivity

Objective

Given that helminth infections have been shown to improve insulin sensitivity in animal studies, which may be explained by beneficial effects on energy balance or by a shift in the immune system to an anti-inflammatory profile, we investigated whether soil-transmitted helminth (STH)-infected subjects are more insulin sensitive than STH-uninfected subjects.

Design

We performed a cross-sectional study on Flores island, Indonesia, an area with high prevalence of STH infections.

Methods

From 646 adults, stool samples were screened for Trichuris trichiura by microscopy and for Ascaris lumbricoides, Necator americanus, Ancylostoma duodenale, and Strongyloides stercoralis by qPCR. No other helminth was found. We collected data on body mass index (BMI, kg/m²), waist-to-hip ratio (WHR), fasting blood glucose (FBG, mmol/L), insulin (pmol/L), high sensitive C-reactive protein (ng/ml) and Immunoglobulin E (IU/ml). The homeostatic model assessment for insulin resistance (HOMAIR) was calculated and regression models were used to assess the association between STH infection status and insulin resistance.

Results

424 (66%) participants had at least one STH infection. STH infected participants had lower BMI (23.2 vs 22.5 kg/m², p value = 0.03) and lower HOMAIR (0.97 vs 0.81, p value = 0.05). In an age-, sex- and BMI-adjusted model a significant association was seen between the number of infections and HOMAIR: for every additional infection with STH species, the HOMAIR decreased by 0.10 (p for linear trend 0.01). This effect was mainly accounted for by a decrease in insulin of 4.9 pmol/L for every infection (p for trend = 0.07).

Conclusion

STH infections are associated with a modest improvement of insulin sensitivity, which is not accounted for by STH effects on BMI alone.     

Efficacy of single-dose and triple-dose albendazole and mebendazole against soil-transmitted helminths and Taenia spp.: a randomized controlled trial

Background

The control of soil-transmitted helminth (STH) infections currently relies on the large-scale administration of single-dose oral albendazole or mebendazole. However, these treatment regimens have limited efficacy against hookworm and Trichuris trichiura in terms of cure rates (CR), whereas fecal egg reduction rates (ERR) are generally high for all common STH species. We compared the efficacy of single-dose versus triple-dose treatment against hookworm and other STHs in a community-based randomized controlled trial in the People''s Republic of China.

Methodology/Principal findings

The hookworm CR and fecal ERR were assessed in 314 individuals aged ≥5 years who submitted two stool samples before and 3–4 weeks after administration of single-dose oral albendazole (400 mg) or mebendazole (500 mg) or triple-dose albendazole (3×400 mg over 3 consecutive days) or mebendazole (3×500 mg over 3 consecutive days). Efficacy against T. trichiura, Ascaris lumbricoides, and Taenia spp. was also assessed.Albendazole cured significantly more hookworm infections than mebendazole in both treatment regimens (single dose: respective CRs 69% (95% confidence interval [CI]: 55–81%) and 29% (95% CI: 20–45%); triple dose: respective CRs 92% (95% CI: 81–98%) and 54% (95% CI: 46–71%)). ERRs followed the same pattern (single dose: 97% versus 84%; triple dose: 99.7% versus 96%). Triple-dose regimens outperformed single doses against T. trichiura; three doses of mebendazole – the most efficacious treatment tested – cured 71% (95% CI: 57–82%). Both single and triple doses of either drug were highly efficacious against A. lumbricoides (CR: 93–97%; ERR: all >99.9%). Triple dose regimens cured all Taenia spp. infections, whereas single dose applications cured only half of them.

Conclusions/Significance

Single-dose oral albendazole is more efficacious against hookworm than mebendazole. To achieve high CRs against both hookworm and T. trichiura, triple-dose regimens are warranted.

Trial Registration

www.controlled-trials.com ISRCTN47375023     

Burden of soil-transmitted helminth infection in pregnant refugees and migrants on the Thailand-Myanmar border: Results from a retrospective cohort

BackgroundSoil-transmitted helminth (STH) infections are widespread in tropical and subtropical regions. While many STH infections are asymptomatic, vulnerable populations such as pregnant women face repercussions such as aggravation of maternal anaemia. However, data on prevalence and the effect of STH infections in pregnancy are limited. The aim of this analysis was to describe the burden of STH infections within and between populations of pregnant women from a local refugee camp to a mobile migrant population, and to explore possible associations between STH infection and pregnancy outcomes.MethodologyThis is a retrospective review of records from pregnant refugee and migrant women who attended Shoklo Malaria Research Unit antenatal care (ANC) clinics along the Thailand-Myanmar border between July 2013 and December 2017. Inclusion was based on provision of a stool sample during routine antenatal screening. A semi-quantitative formalin concentration method was employed for examination of faecal samples. The associations between STH mono-infections and maternal anaemia and pregnancy outcomes (i.e., miscarriage, stillbirth, preterm birth, and small for gestational age) were estimated using regression analysis.Principal findingsOverall, 12,742 pregnant women were included, of whom 2,702 (21.2%) had a confirmed infection with either Ascaris lumbricoides, hookworm, Trichuris trichiura, or a combination of these. The occurrence of STH infections in the refugee population (30.8%; 1,246/4,041) was higher than in the migrant population (16.7%; 1,456/8,701). A. lumbricoides was the predominant STH species in refugees and hookworm in migrants. A. lumbricoides and hookworm infection were associated with maternal anaemia at the first ANC consultation with adjusted odds ratios of 1.37 (95% confidence interval (CI) 1.08–1.72) and 1.65 (95% CI 1.19–2.24), respectively. Pregnant women with A. lumbricoides infection were less likely to miscarry when compared to women with negative stool samples (adjusted hazard ratio 0.63, 95% CI 0.48–0.84). STH infections were not significantly associated with stillbirth, preterm birth or being born too small for gestational age. One in five pregnant women in this cohort had STH infection. Association of STH infection with maternal anaemia, in particular in the event of late ANC enrolment, underlines the importance of early detection and treatment of STH infection. A potential protective effect of A. lumbricoides infection on miscarriage needs confirmation in prospective studies.     

Maternal geohelminth infections are associated with an increased susceptibility to geohelminth infection in children: a case-control study

Background

Children of mothers infected with soil-transmitted helminths (STH) may have an increased susceptibility to STH infection.

Methods and Findings

We did a case-control study nested in a birth cohort in Ecuador. Data from 1,004 children aged 7 months to 3 years were analyzed. Cases were defined as children with Ascaris lumbricoides and/or Trichuris trichiura, controls without. Exposure was defined as maternal infection with A. lumbricoides and/or T. trichiura, detected during the third trimester of pregnancy. The analysis was restricted to households with a documented infection to control for infection risk. Children of mothers with STH infections had a greater risk of infection compared to children of uninfected mothers (adjusted OR 2.61, 95% CI: 1.88–3.63, p<0.001). This effect was particularly strong in children of mothers with both STH infections (adjusted OR: 5.91, 95% CI: 3.55–9.81, p<0.001). Newborns of infected mothers had greater levels of plasma IL-10 than those of uninfected mothers (p = 0.033), and there was evidence that cord blood IL-10 was increased among newborns who became infected later in childhood (p = 0.060).

Conclusion

Our data suggest that maternal STH infections increase susceptibility to infection during early childhood, an effect that was associated with elevated IL-10 in cord plasma.     

Pilot Assessment of Soil-Transmitted Helminthiasis in the Context of Transmission Assessment Surveys for Lymphatic Filariasis in Benin and Tonga

Background

Mass drug administration (MDA) for lymphatic filariasis (LF) programs has delivered more than 2 billion treatments of albendazole, in combination with either ivermectin or diethylcarbamazine, to communities co-endemic for soil-transmitted helminthiasis (STH), reducing the prevalence of both diseases. A transmission assessment survey (TAS) is recommended to determine if MDA for LF can be stopped within an evaluation unit (EU) after at least five rounds of annual treatment. The TAS also provides an opportunity to simultaneously assess the impact of these MDAs on STH and to determine the frequency of school-based MDA for STH after community-wide MDA is no longer needed for LF.

Methodology/Principal Findings

Pilot studies conducted in Benin and Tonga assessed the feasibility of a coordinated approach. Of the schools (clusters) selected for a TAS in each EU, a subset of 5 schools per STH ecological zone was randomly selected, according to World Health Organization (WHO) guidelines, for the coordinated survey. In Benin, 519 children were sampled in 5 schools and 22 (4.2%) had STH infection (A. lumbricoides, T. trichiura, or hookworm) detected using the Kato-Katz method. All infections were classified as light intensity under WHO criteria. In Tonga, 10 schools were chosen for the coordinated TAS and STH survey covering two ecological zones; 32 of 232 (13.8%) children were infected in Tongatapu and 82 of 320 (25.6%) in Vava''u and Ha''apai. All infections were light-intensity with the exception of one with moderate-intensity T. trichiura.

Conclusions

Synchronous assessment of STH with TAS is feasible and provides a well-timed evaluation of infection prevalence to guide ongoing treatment decisions at a time when MDA for LF may be stopped. The coordinated field experiences in both countries also suggest potential time and cost savings. Refinement of a coordinated TAS and STH sampling methodology should be pursued, along with further validation of alternative quantitative diagnostic tests for STH that can be used with preserved stool specimens.     

Efficacy and side effects of albendazole currently in use against Ascaris,Trichuris and hookworm among school children in Wondo Genet,southern Ethiopia

Monitoring the efficacy of anthelminthic drugs is essential. The objective of this study was to assess the efficacy of a single oral dose of 400 mg albendazole (ABZ) against the major soil-transmitted helminth (STH) infection in school children, Wondo Genet, southern Ethiopia. A single fresh stool sample was collected from 298 school children and examined using a duplicate smear of the Kato–Katz method. Children positive for STH infections were treated with single oral dose of 400 mg ABZ and re-examined for intestinal helminth infections 21 days post-treatment. The participants were interviewed for symptoms related with the drug uptake 24 h after ABZ treatment. Children positive for Schistosoma mansoni infections were treated with Praziquantel (40 mg/kg of body weight) after an ABZ treatment follow up survey. 51.3%, 49.7%, 44.6% and 88.3% had hookworm, Ascaris lumbricoides, Trichuris trichiura and any intestinal helminth infection, respectively. Cure rates were 97.4% for hookworm, 96.6% for A. lumbricoides and 30.8% for T. trichiura infections. Egg reduction rates (ERRs) were 99.8% for hookworm, 99.9% for A. lumbricoides and 83.1% for T. trichiura infections. Mild and transient symptoms were observed among the participants which were quite frequent. In conclusion, a 400 mg single oral dose of ABZ was effective against hookworm and A. lumbricoides but less efficacious against T. trichiura infection. The drug resulted in high ERRs for hookworm, A. lumbricoides and T. trichiura. Administration of the drug in repeated doses or in combination with other drugs might be necessary.     

The spatial-temporal distribution of soil-transmitted helminth infections in Guangdong Province,China: A geostatistical analysis of data derived from the three national parasitic surveys

BackgroundThe results of the latest national survey on important human parasitic diseases in 2015–2016 showed Guangdong Province is still a moderately endemic area, with the weighted prevalence of soil-transmitted helminths (STHs) higher than the national average. High-resolution age- and gender-specific spatial-temporal risk maps can support the prevention and control of STHs, but not yet available in Guangdong.MethodologyGeoreferenced age- and gender-specific disease data of STH infections in Guangdong Province was derived from three national surveys on important human parasitic diseases, conducted in 1988–1992, 2002–2003, and 2015–2016, respectively. Potential influencing factors (e.g., environmental and socioeconomic factors) were collected from open-access databases. Bayesian geostatistical models were developed to analyze the above data, based on which, high-resolution maps depicting the STH infection risk were produced in the three survey years in Guangdong Province.Principal findingsThere were 120, 31, 71 survey locations in the first, second, and third national survey in Guangdong, respectively. The overall population-weighted prevalence of STH infections decreased significantly over time, from 68.66% (95% Bayesian credible interval, BCI: 64.51–73.06%) in 1988–1992 to 0.97% (95% BCI: 0.69–1.49%) in 2015–2016. In 2015–2016, only low to moderate infection risk were found across Guangdong, with hookworm becoming the dominant species. Areas with relatively higher risk (>5%) were mostly distributed in the western region. Females had higher infection risk of STHs than males. The infection risk of A. lumbricoides and T. trichiura were higher in children, while middle-aged and elderly people had higher infection risk of hookworm. Precipitation, elevation, land cover, and human influence index (HII) were significantly related with STH infection risk.Conclusions/SignificanceWe produced the high-resolution, age- and gender-specific risk maps of STH infections in the three national survey periods across nearly 30 years in Guangdong Province, which can provide important information assisting the control and prevention strategies.     

Soil-transmitted helminth reinfection after drug treatment: a systematic review and meta-analysis

Background

Soil-transmitted helminth (STH) infections (i.e., Ascaris lumbricoides, hookworm, and Trichuris trichiura) affect more than a billion people. Preventive chemotherapy (i.e., repeated administration of anthelmintic drugs to at-risk populations), is the mainstay of control. This strategy, however, does not prevent reinfection. We performed a systematic review and meta-analysis to assess patterns and dynamics of STH reinfection after drug treatment.

Methodology

We systematically searched PubMed, ISI Web of Science, EMBASE, Cochrane Database of Systematic Reviews, China National Knowledge Infrastructure, WanFang Database, Chinese Scientific Journal Database, and Google Scholar. Information on study year, country, sample size, age of participants, diagnostic method, drug administration strategy, prevalence and intensity of infection pre- and posttreatment, cure and egg reduction rate, evaluation period posttreatment, and adherence was extracted. Pooled risk ratios from random-effects models were used to assess the risk of STH reinfection after treatment. Our protocol is available on PROSPERO, registration number: CRD42011001678.

Principal Findings

From 154 studies identified, 51 were included and 24 provided STH infection rates pre- and posttreatment, whereas 42 reported determinants of predisposition to reinfection. At 3, 6, and 12 months posttreatment, A. lumbricoides prevalence reached 26% (95% confidence interval (CI): 16–43%), 68% (95% CI: 60–76%) and 94% (95% CI: 88–100%) of pretreatment levels, respectively. For T. trichiura, respective reinfection prevalence were 36% (95% CI: 28–47%), 67% (95% CI: 42–100%), and 82% (95% CI: 62–100%), and for hookworm, 30% (95% CI: 26–34%), 55% (95% CI: 34–87%), and 57% (95% CI: 49–67%). Prevalence and intensity of reinfection were positively correlated with pretreatment infection status.

Conclusion

STH reinfections occur rapidly after treatment, particularly for A. lumbricoides and T. trichiura. Hence, there is a need for frequent anthelmintic drug administrations to maximize the benefit of preventive chemotherapy. Integrated control approaches emphasizing health education and environmental sanitation are needed to interrupt transmission of STH.     

The effectiveness of 4 monthly albendazole treatment in the reduction of soil-transmitted helminth infections in women of reproductive age in Viet Nam

Soil-transmitted helminth (STH) infections are endemic in northern Viet Nam where the climate and agricultural practices, such as the use of human excreta as fertiliser and the use of wastewater for irrigation, favour transmission. An intervention was conducted in Yen Bai Province, north-west Viet Nam, to measure the effectiveness of single dose albendazole (400 mg) administered every 4 months for reducing the prevalence of STH infections in women of reproductive age. Stool samples were collected from women before the intervention and 3 and 12 months post-intervention. Information on a range of demographic and socio-economic variables was also collected to measure the major risk factors for high STH burden in this area. The prevalence of hookworm, Ascaris lumbricoides and Trichuris trichiura infection in the baseline sample of 366 women were 76.2%, 19.2% and 29.1%, respectively. In the women who were surveyed at baseline and again at 3 and 12 months after the intervention (n = 118) cure rates were 71.3% for hookworm, 87.0% for A. lumbricoides and 81.4% for T. trichiura by the end of the 12 month study period (i.e. after three doses of albendazole). The main risk factor for hookworm infection was if women worked outside (odds ratio (OR) = 3.2 (95% Confidence Interval (CI) 1.6-6.2), P = 0.001) and the major risk factor for A. lumbricoides and T. trichiura infection was a lack of education. Low educational attainment was also the strongest risk factor for co-infection with all three species of STH (OR = 7.5 (95% CI 3.4-16.4), P < 0.001). The high rates of hookworm infection in this area of Viet Nam and the high cure rates for all three species of STH with 4 monthly albendazole treatment suggest that this programme should be expanded to all endemic areas in Viet Nam. The study also highlights the important contribution of education to women’s health.     

Estimating the sensitivity and specificity of Kato-Katz stool examination technique for detection of hookworms, Ascaris lumbricoides and Trichuris trichiura infections in humans in the absence of a ‘gold standard’

The accuracy of the Kato-Katz technique in identifying individuals with soil-transmitted helminth (STH) infections is limited by day-to-day variation in helminth egg excretion, confusion with other parasites and the laboratory technicians’ experience. We aimed to estimate the sensitivity and specificity of the Kato-Katz technique to detect infection with Ascaris lumbricoides, hookworm and Trichuris trichiura using a Bayesian approach in the absence of a ‘gold standard’. Data were obtained from a longitudinal study conducted between January 2004 and December 2005 in Samar Province, the Philippines. Each participant provided between one and three stool samples over consecutive days. Stool samples were examined using the Kato-Katz technique and reported as positive or negative for STHs. In the presence of measurement error, the true status of each individual is considered as latent data. Using a Bayesian method, we calculated marginal posterior densities of sensitivity and specificity parameters from the product of the likelihood function of observed and latent data. A uniform prior distribution was used (beta distribution: α = 1, β = 1). A total of 5624 individuals provided at least one stool sample. One, two and three stool samples were provided by 1582, 1893 and 2149 individuals, respectively. All STHs showed variation in test results from day to day. Sensitivity estimates of the Kato-Katz technique for one stool sample were 96.9% (95% Bayesian Credible Interval [BCI]: 96.1%, 97.6%), 65.2% (60.0%, 69.8%) and 91.4% (90.5%, 92.3%), for A. lumbricoides, hookworm and T. trichiura, respectively. Specificity estimates for one stool sample were 96.1% (95.5%, 96.7%), 93.8% (92.4%, 95.4%) and 94.4% (93.2%, 95.5%), for A. lumbricoides, hookworm and T. trichiura, respectively. Our results show that the Kato-Katz technique can perform with reasonable accuracy with one day’s stool collection for A. lumbricoides and T. trichiura. Low sensitivity of the Kato-Katz for detection of hookworm infection may be related to rapid degeneration of delicate hookworm eggs with time.