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.     

Bayesian Geostatistical Model-Based Estimates of Soil-Transmitted Helminth Infection in Nigeria,Including Annual Deworming Requirements

Background

The acceleration of the control of soil-transmitted helminth (STH) infections in Nigeria, emphasizing preventive chemotherapy, has become imperative in light of the global fight against neglected tropical diseases. Predictive risk maps are an important tool to guide and support control activities.

Methodology

STH infection prevalence data were obtained from surveys carried out in 2011 using standard protocols. Data were geo-referenced and collated in a nationwide, geographic information system database. Bayesian geostatistical models with remotely sensed environmental covariates and variable selection procedures were utilized to predict the spatial distribution of STH infections in Nigeria.

Principal Findings

We found that hookworm, Ascaris lumbricoides, and Trichuris trichiura infections are endemic in 482 (86.8%), 305 (55.0%), and 55 (9.9%) locations, respectively. Hookworm and A. lumbricoides infection co-exist in 16 states, while the three species are co-endemic in 12 states. Overall, STHs are endemic in 20 of the 36 states of Nigeria, including the Federal Capital Territory of Abuja. The observed prevalence at endemic locations ranged from 1.7% to 51.7% for hookworm, from 1.6% to 77.8% for A. lumbricoides, and from 1.0% to 25.5% for T. trichiura. Model-based predictions ranged from 0.7% to 51.0% for hookworm, from 0.1% to 82.6% for A. lumbricoides, and from 0.0% to 18.5% for T. trichiura. Our models suggest that day land surface temperature and dense vegetation are important predictors of the spatial distribution of STH infection in Nigeria. In 2011, a total of 5.7 million (13.8%) school-aged children were predicted to be infected with STHs in Nigeria. Mass treatment at the local government area level for annual or bi-annual treatment of the school-aged population in Nigeria in 2011, based on World Health Organization prevalence thresholds, were estimated at 10.2 million tablets.

Conclusions/Significance

The predictive risk maps and estimated deworming needs presented here will be helpful for escalating the control and spatial targeting of interventions against STH infections in Nigeria.     

Impact of Anti-Retroviral Treatment and Cotrimoxazole Prophylaxis on Helminth Infections in HIV-Infected Patients in Lambaréné, Gabon

Background

Foci of the HIV epidemic and helminthic infections largely overlap geographically. Treatment options for helminth infections are limited, and there is a paucity of drug-development research in this area. Limited evidence suggests that antiretroviral therapy (ART) reduces prevalence of helminth infections in HIV-infected individuals. We investigated whether ART exposure and cotrimoxazole preventive therapy (CTX-P) is associated with a reduced prevalence of helminth infections.

Methodology and Principal Findings

This cross-sectional study was conducted at a primary HIV-clinic in Lambaréné, Gabon. HIV-infected adults who were ART-naïve or exposed to ART for at least 3 months submitted one blood sample and stool and urine samples on 3 consecutive days. Outcome was helminth infection with intestinal helminths, Schistosoma haematobium, Loa loa or Mansonella perstans. Multivariable logistic regression was used to assess associations between ART or CTX-P and helminth infection. In total, 408 patients were enrolled. Helminth infection was common (77/252 [30.5%]). Filarial infections were most prevalent (55/310 [17.7%]), followed by infection with intestinal helminths (35/296 [11.8%]) and S. haematobium (19/323 [5.9%]). Patients on CTX-P had a reduced risk of Loa loa microfilaremia (adjusted odds ratio (aOR) 0.47, 95% CI 0.23-0.97, P = 0.04), also in the subgroup of patients on ART (aOR 0.36, 95% CI 0.13-0.96, P = 0.04). There was no effect of ART exposure on helminth infection prevalence.

Conclusions/Significance

CTX-P use was associated with a decreased risk of Loa loa infection, suggesting an anthelminthic effect of antifolate drugs. No relation between ART use and helminth infections was established.     

Treatment for Schistosoma japonicum, reduction of intestinal parasite load, and cognitive test score improvements in school-aged children

Background

To determine whether treatment of intestinal parasitic infections improves cognitive function in school-aged children, we examined changes in cognitive testscores over 18 months in relation to: (i) treatment-related Schistosoma japonicum intensity decline, (ii) spontaneous reduction of single soil-transmitted helminth (STH) species, and (iii) ≥2 STH infections among 253 S. japonicum-infected children.

Methodology

Helminth infections were assessed at baseline and quarterly by the Kato-Katz method. S. japonicum infection was treated at baseline using praziquantel. An intensity-based indicator of lower vs. no change/higher infection was defined separately for each helminth species and joint intensity declines of ≥2 STH species. In addition, S. japonicum infection-free duration was defined in four categories based on time of schistosome re-infection: >18 (i.e. cured), >12 to ≤18, 6 to ≤12 and ≤6 (persistently infected) months. There was no baseline treatment for STHs but their intensity varied possibly due to spontaneous infection clearance/acquisition. Four cognitive tests were administered at baseline, 6, 12, and 18 months following S. japonicum treatment: learning and memory domains of Wide Range Assessment of Memory and Learning (WRAML), verbal fluency (VF), and Philippine nonverbal intelligence test (PNIT). Linear regression models were used to relate changes in respective infections to test performance with adjustment for sociodemographic confounders and coincident helminth infections.

Principal Findings

Children cured (β = 5.8; P = 0.02) and those schistosome-free for >12 months (β = 1.5; P = 0.03) scored higher in WRAML memory and VF tests compared to persistently infected children independent of STH infections. A decline vs. no change/increase of any individual STH species (β:11.5–14.5; all P<0.01) and the joint decline of ≥2 STH (β = 13.1; P = 0.01) species were associated with higher scores in WRAML learning test independent of schistosome infection. Hookworm and Trichuris trichiura declines were independently associated with improvements in WRAML memory scores as was the joint decline in ≥2 STH species. Baseline coinfection by ≥2 STH species was associated with low PNIT scores (β = −1.9; P = 0.04).

Conclusion/Significance

Children cured/S. japonicum-free for >12 months post-treatment and those who experienced declines of ≥2 STH species scored higher in three of four cognitive tests. Our result suggests that sustained deworming and simultaneous control for schistosome and STH infections could improve children''s ability to take advantage of educational opportunities in helminth-endemic regions.     

Malaria and Helminth Co-Infections in School and Preschool Children: A Cross-Sectional Study in Magu District,North-Western Tanzania

Background

Malaria, schistosomiasis and soil transmitted helminth infections (STH) are important parasitic infections in Sub-Saharan Africa where a significant proportion of people are exposed to co-infections of more than one parasite. In Tanzania, these infections are a major public health problem particularly in school and pre-school children. The current study investigated malaria and helminth co-infections and anaemia in school and pre-school children in Magu district, Tanzania.

Methodology

School and pre-school children were enrolled in a cross-sectional study. Stool samples were examined for Schistosoma mansoni and STH infections using Kato Katz technique. Urine samples were examined for Schistosoma haematobium using the urine filtration method. Blood samples were examined for malaria parasites and haemoglobin concentrations using the Giemsa stain and Haemoque methods, respectively.

Principal Findings

Out of 1,546 children examined, 1,079 (69.8%) were infected with one or more parasites. Malaria-helminth co-infections were observed in 276 children (60% of all children with P. falciparum infection). Malaria parasites were significantly more prevalent in hookworm infected children than in hookworm free children (p = 0.046). However, this association was non-significant on multivariate logistic regression analysis (OR = 1.320, p = 0.064). Malaria parasite density decreased with increasing infection intensity of S. mansoni and with increasing number of co-infecting helminth species. Anaemia prevalence was 34.4% and was significantly associated with malaria infection, S. haematobium infection and with multiple parasite infections. Whereas S. mansoni infection was a significant predictor of malaria parasite density, P. falciparum and S. haematobium infections were significant predictors of anaemia.

Conclusions/Significance

These findings suggest that multiple parasite infections are common in school and pre-school children in Magu district. Concurrent P. falciparum, S. mansoni and S. haematobium infections increase the risk of lower Hb levels and anaemia, which in turn calls for integrated disease control interventions. The associations between malaria and helminth infections detected in this study need further investigation.     

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.     

IL-10- and TGFβ-mediated Th9 Responses in a Human Helminth Infection

Background

Th9 cells are a subset of CD4⁺ T cells that express the protoypical cytokine, IL-9. Th9 cells are known to effect protective immunity in animal models of intestinal helminth infections. However, the role of Th9 cells in human intestinal helminth infections has never been examined.

Methodology

To examine the role of Th9 cells in Strongyloidis stercoralis (Ss), a common intestinal helminth infection, we compared the frequency of Th9 expressing IL-9 either singly (mono-functional) or co-expressing IL-4 or IL-10 (dual-functional) in Ss-infected individuals (INF) to frequencies in uninfected (UN) individuals.

Principal Findings

INF individuals exhibited a significant increase in the spontaneously expressed and/or antigen specific frequencies of both mono- and dual-functional Th9 cells as well as Th2 cells expressing IL-9 compared to UN. The differences in Th9 induction between INF and UN individuals was predominantly antigen-specific as the differences were no longer seen following control antigen or mitogen stimulation. In addition, the increased frequency of Th9 cells in response to parasite antigens was dependent on IL-10 and TGFx since neutralization of either of these cytokines resulted in diminished Th9 frequencies. Finally, following successful treatment of Ss infection, the frequencies of antigen-specific Th9 cells diminished in INF individuals, suggesting a role for the Th9 response in active Ss infection. Moreover, IL-9 levels in whole blood culture supernatants following Ss antigen stimulation were higher in INF compared to UN individuals.

Conclusion

Thus, Ss infection is characterized by an IL-10- and TGFβ dependent expansion of Th9 cells, an expansion found to reversible by anti-helmintic treatment.     

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.     

Application of a Multiplex Quantitative PCR to Assess Prevalence and Intensity Of Intestinal Parasite Infections in a Controlled Clinical Trial

Background

Accurate quantitative assessment of infection with soil transmitted helminths and protozoa is key to the interpretation of epidemiologic studies of these parasites, as well as for monitoring large scale treatment efficacy and effectiveness studies. As morbidity and transmission of helminth infections are directly related to both the prevalence and intensity of infection, there is particular need for improved techniques for assessment of infection intensity for both purposes. The current study aimed to evaluate two multiplex PCR assays to determine prevalence and intensity of intestinal parasite infections, and compare them to standard microscopy.

Methodology/Principal Findings

Faecal samples were collected from a total of 680 people, originating from rural communities in Timor-Leste (467 samples) and Cambodia (213 samples). DNA was extracted from stool samples and subject to two multiplex real-time PCR reactions the first targeting: Necator americanus, Ancylostoma spp., Ascaris spp., and Trichuris trichiura; and the second Entamoeba histolytica, Cryptosporidium spp., Giardia. duodenalis, and Strongyloides stercoralis. Samples were also subject to sodium nitrate flotation for identification and quantification of STH eggs, and zinc sulphate centrifugal flotation for detection of protozoan parasites. Higher parasite prevalence was detected by multiplex PCR (hookworms 2.9 times higher, Ascaris 1.2, Giardia 1.6, along with superior polyparasitism detection with this effect magnified as the number of parasites present increased (one: 40.2% vs. 38.1%, two: 30.9% vs. 12.9%, three: 7.6% vs. 0.4%, four: 0.4% vs. 0%). Although, all STH positive samples were low intensity infections by microscopy as defined by WHO guidelines the DNA-load detected by multiplex PCR suggested higher intensity infections.

Conclusions/Significance

Multiplex PCR, in addition to superior sensitivity, enabled more accurate determination of infection intensity for Ascaris, hookworms and Giardia compared to microscopy, especially in samples exhibiting polyparasitism. The superior performance of multiplex PCR to detect polyparasitism and more accurately determine infection intensity suggests that it is a more appropriate technique for use in epidemiologic studies and for monitoring large-scale intervention trials.     

Earlier Menarche Is Associated with Lower Insulin Sensitivity and Increased Adiposity in Young Adult Women

Objective

We aimed to assess whether age at menarche was associated with insulin sensitivity in young adult women.

Methods

We studied 54 healthy young women aged 20–30 years. Participants were grouped according to age at menarche: Early (≤11.0 years; n=13), Average (>12.0 and ≤13.0 years; n=28), and Late (≥14.0 years, n=13). Primary outcome was insulin sensitivity measured using intravenous glucose tolerance tests and Bergman’s minimal model. Body composition was assessed using whole-body dual-energy X-ray absorptiometry.

Results

Earlier menarche was associated with lower insulin sensitivity (p=0.015). There was also a continuous increase in adiposity with younger age at menarche, which was associated with increased weight (p=0.001), BMI (p=0.002), total body fat (p=0.049), and truncal fat (p=0.020). Stratified analyses showed that insulin sensitivity in Early women (5.5 x10^-4·min^-1(mU/l)) was lower than in Average (8.0 x10^-4·min^-1(mU/l), p=0.021) and Late (8.6 x10^-4·min^-1(mU/l), p=0.033) groups. Early women (weight=66.1 kg; BMI=24.1 kg/m²) were considerably heavier and fatter than Average (59.0 kg, p=0.004; 21.4 kg/m², p=0.002) and Late (57.0 kg, p=0.001; 20.8 kg/m², p=0.0009) women.

Conclusions

Early menarche is associated with lower insulin sensitivity and increased adiposity in young adulthood, potentially increasing the risk of type 2 diabetes and the metabolic syndrome later in life.     

Podoconiosis and Soil-Transmitted Helminths (STHs): Double Burden of Neglected Tropical Diseases in Wolaita Zone,Rural Southern Ethiopia

Background

Both podoconiosis and soil-transmitted helminth (STH) infections occur among barefoot people in areas of extreme poverty; however, their co-morbidity has not previously been investigated. We explored the overlap of STH infection and podoconiosis in Southern Ethiopia and quantified their separate and combined effects on prevalent anemia and hemoglobin levels in podoconiosis patients and health controls from the same area.

Methods and Principal Findings

A two-part comparative cross-sectional study was conducted in Wolaita zone, southern Ethiopia. Data were collected from adult patients presenting with clinically confirmed podoconiosis, and unmatched adult neighborhood controls living in the same administrative area. Information on demographic and selected lifestyle factors was collected using interviewer-administered questionnaires. Stool samples were collected and examined qualitatively using the modified formalin-ether sedimentation method. Hemoglobin level was determined using two different methods: hemoglobinometer and automated hematology analyzer. A total of 913 study subjects (677 podoconiosis patients and 236 controls) participated. The prevalence of any STH infection was 47.6% among patients and 33.1% among controls (p<0.001). The prevalence of both hookworm and Trichuris trichiura infections was significantly higher in podoconiosis patients than in controls (AOR 1.74, 95% CI 1.25 to2.42, AOR 6.53, 95% CI 2.34 to 18.22, respectively). Not wearing shoes and being a farmer remained significant independent predictors of infection with any STH. There was a significant interaction between STH infection and podoconiosis on reduction of hemoglobin level (interaction p value = 0.002).

Conclusions

Prevalence of any STH and hookworm infection was higher among podoconiosis patients than among controls. A significant reduction in hemoglobin level was observed among podoconiosis patients co-infected with hookworm and ‘non-hookworm STH’. Promotion of consistent shoe-wearing practices may have double advantages in controlling both podoconiosis and hookworm infection in the study area.     

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.     

Asymptomatic Helminth Infection in Active Tuberculosis Is Associated with Increased Regulatory and Th-2 Responses and a Lower Sputum Smear Positivity

Background

The impact of intestinal helminth infection on the clinical presentation and immune response during active tuberculosis (TB) infection is not well characterized. Our aim was to investigate whether asymptomatic intestinal helminth infection alters the clinical signs and symptoms as well as the cell mediated immune responses in patients with active TB.

Methodology

Consecutive, newly diagnosed TB patients and healthy community controls (CCs) were recruited in North-west Ethiopia. TB-score, body mass index and stool samples were analyzed. Cells from HIV-negative TB patients (HIV-/TB) and from CCs were analyzed for regulatory T-cells (Tregs) and cytokine responses using flow cytometry and ELISPOT, respectively.

Results

A significantly higher ratio of helminth co-infection was observed in TB patients without HIV (Helm+/HIV-/TB) compared to HIV negative CCs, (40% (121/306) versus 28% (85/306), p = 0.003). Helm+/HIV-/TB patients showed significantly increased IL-5 secreting cells compared to Helm-/HIV-/TB (37 SFU (IQR:13–103) versus 2 SFU (1–50); p = 0.02, n = 30). Likewise, levels of absolute Tregs (9.4 (3.2–16.7) cells/μl versus 2.4 (1.1–4.0) cells/μl; p = 0.041) and IL-10 secreting cells (65 SFU (7–196) versus 1 SFU (0–31); p = 0.014) were significantly higher in Helm+/HIV-/TB patients compared to Helm-/HIV-/TB patients. In a multivariate analysis, a lower rate of sputum smear positivity for acid fast bacilli, lower body temperature, and eosinophilia were independently associated with helminth infection in TB patients.

Conclusions

Asymptomatic helminth infection is associated with increased regulatory T-cell and Th2-type responses and a lower rate of sputum smear positivity. Further studies are warranted to investigate the clinical and immunological impact of helminth infection in TB patients.     

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.     

A Scoping Review and Prevalence Analysis of Soil-Transmitted Helminth Infections in Honduras

Background

Honduras is endemic for soil-transmitted helminth (STH) infections, but critical information gaps still remain on the prevalence and intensity of these infections as well as on their spatial distribution at subnational levels.

Objectives

Firstly, to review the research activity on STH infections in Honduras and secondly, to carry out a national prevalence analysis and map the geographical distribution of these infections in children.

Methods

A systematic search was conducted of the published and grey literature to identify scientific work on the impact and prevalence of STH infections done between May 1930 and June 30, 2012. International databases and Honduran journals were searched. Grey literature was gleaned from local libraries and key informants. Select studies conducted between 2001 and 2012 were used to produce prevalence maps and to investigate association between STH prevalence and socio-economic and environmental factors.

Results

Of 257 identified studies, 211 (21.4% peer-reviewed) were retained for analysis and categorized as clinical research (10.9%), treatment efficacy studies (8.1%) or epidemiological studies (81%). Prevalence analysis and geographical mapping included 36 epidemiological studies from Honduras''s 18 departments and 23% of its municipalities. Overall STH prevalence was >50% in 40.6% of municipalities. Prevalences above 20% for each trichuriasis, ascariasis, and hookworm infection were found in 68%, 47.8%, and 7.2% of studied municipalities, respectively. Municipalities with lower human development index, less access to of potable water, and with higher annual precipitation showed higher STH prevalences.

Conclusions

This is the first study to provide a comprehensive historic review of STH research activity and prevalence in Honduras, revealing important knowledge gaps related to infection risk factors, disease burden, and anti-parasitic drug efficacy, among others. Our decade-long prevalence analysis reveals geographical differences in STH prevalence and these findings suggest that differential intervention strategies might be necessary in Honduras for the control of these infections.     

Helminth-Associated Systemic Immune Activation and HIV Co-receptor Expression: Response to Albendazole/Praziquantel Treatment

Background

It has been hypothesized that helminth infections increase HIV susceptibility by enhancing systemic immune activation and hence contribute to elevated HIV-1 transmission in sub-Saharan Africa.

Objective

To study systemic immune activation and HIV-1 co-receptor expression in relation to different helminth infections and in response to helminth treatment.

Methods

HIV-negative adults with (n = 189) or without (n = 57) different helminth infections, as diagnosed by Kato-Katz, were enrolled in Mbeya, Tanzania. Blinded to helminth infection status, T cell differentiation (CD45RO, CD27), activation (HLA-DR, CD38) and CCR5 expression was determined at baseline and 3 months after Albendazole/Praziquantel treatment. Plasma cytokine levels were compared using a cytometric bead array.

Results

Trichuris and Ascaris infections were linked to increased frequencies of “activated” CD4 and/or CD8 T cells (p<0.05), whereas Hookworm infection was associated with a trend towards decreased HLA-DR⁺ CD8 T cell frequencies (p = 0.222). In Trichuris infected subjects, there was a linear correlation between HLA-DR⁺ CD4 T cell frequencies and the cytokines IL-1β and IL-10 (p<0.05). Helminth treatment with Albendazole and Praziquantel significantly decreased eosinophilia for S. mansoni and Hookworm infections (p<0.005) but not for Trichuris infection and only moderately modulated T cell activation. CCR5 surface density on memory CD4 T cells was increased by 1.2-fold during Trichuris infection (p-value: 0.053) and reduced after treatment (p = 0.003).

Conclusions

Increased expression of T cell activation markers was associated with Trichuris and Ascaris infections with relatively little effect of helminth treatment.     

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.     

Soil-Transmitted Helminth Infections and Nutritional Status in School-age Children from Rural Communities in Honduras

Background

Soil-transmitted helminth (STH) infections are endemic in Honduras and efforts are underway to decrease their transmission. However, current evidence is lacking in regards to their prevalence, intensity and their impact on children''s health.

Objectives

To evaluate the prevalence and intensity of STH infections and their association with nutritional status in a sample of Honduran children.

Methodology

A cross-sectional study was done among school-age children residing in rural communities in Honduras, in 2011. Demographic data was obtained, hemoglobin and protein concentrations were determined in blood samples and STH infections investigated in single-stool samples by Kato-Katz. Anthropometric measurements were taken to calculate height-for-age (HAZ), BMI-for-age (BAZ) and weight-for-age (WAZ) to determine stunting, thinness and underweight, respectively.

Results

Among 320 children studied (48% girls, aged 7–14 years, mean 9.76±1.4) an overall STH prevalence of 72.5% was found. Children >10 years of age were generally more infected than 7–10 year-olds (p = 0.015). Prevalence was 30%, 67% and 16% for Ascaris, Trichuris and hookworms, respectively. Moderate-to-heavy infections as well as polyparasitism were common among the infected children (36% and 44%, respectively). Polyparasitism was four times more likely to occur in children attending schools with absent or annual deworming schedules than in pupils attending schools deworming twice a year (p<0.001). Stunting was observed in 5.6% of children and it was associated with increasing age. Also, 2.2% of studied children were thin, 1.3% underweight and 2.2% had anemia. Moderate-to-heavy infections and polyparasitism were significantly associated with decreased values in WAZ and marginally associated with decreased values in HAZ.

Conclusions

STH infections remain a public health concern in Honduras and despite current efforts were highly prevalent in the studied community. The role of multiparasite STH infections in undermining children''s nutritional status warrants more research.     

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.     

Assessing the impact of misclassification error on an epidemiological association between two helminthic infections

Background

Polyparasitism can lead to severe disability in endemic populations. Yet, the association between soil-transmitted helminth (STH) and the cumulative incidence of Schistosoma japonicum infection has not been described. The aim of this work was to quantify the effect of misclassification error, which occurs when less than 100% accurate tests are used, in STH and S. japonicum infection status on the estimation of this association.

Methodology/Principal Findings

Longitudinal data from 2276 participants in 50 villages in Samar province, Philippines treated at baseline for S. japonicum infection and followed for one year, served as the basis for this analysis. Participants provided 1–3 stool samples at baseline and 12 months later (2004–2005) to detect infections with STH and S. japonicum using the Kato-Katz technique. Variation from day-to-day in the excretion of eggs in feces introduces individual variations in the sensitivity and specificity of the Kato-Katz to detect infection. Bayesian logit models were used to take this variation into account and to investigate the impact of misclassification error on the association between these infections. Uniform priors for sensitivity and specificity of the diagnostic test to detect the three STH and S. japonicum were used. All results were adjusted for age, sex, occupation, and village-level clustering. Without correction for misclassification error, the odds ratios (ORs) between hookworm, Ascaris lumbricoides, and Trichuris trichiura, and S. japonicum infections were 1.28 (95% Bayesian credible intervals: 0.93, 1.76), 0.91 (95% BCI: 0.66, 1.26), and 1.11 (95% BCI: 0.80, 1.55), respectively, and 2.13 (95% BCI: 1.16, 4.08), 0.74 (95% BCI: 0.43, 1.25), and 1.32 (95% BCI: 0.80, 2.27), respectively, after correction for misclassification error for both exposure and outcome.

Conclusions/Significance

The misclassification bias increased with decreasing test accuracy. Hookworm infection was found to be associated with increased 12-month cumulative incidence of S. japonicum infection after correction for misclassification error. Such important associations might be missed in analyses which do not adjust for misclassification errors.