Effect of Deworming on Indices of Health, Cognition, and Education Among Schoolchildren in Rural China: A Cluster-Randomized Controlled Trial

Decreased Weight-for-Age Associated with Mass Deworming among Young Ethiopian Schoolchildren in Jimma Town, Southwest Ethiopia: A School-Based Cross-Sectional Study

School-based mass deworming programs are implemented to reduce soil-transmitted helminth (STH) infection prevalence and intensity among school-aged children. However, previous studies debate the impact of deworming beyond the removal of worms. Hence, this study aimed to examine the effect of mass deworming on nutritional indicators in young Ethiopian schoolchildren. A school-based cross-sectional study was conducted among 1,036 participants from April to May 2020 in Jimma Town, Ethiopia. An interviewer-based questionnaire was administered to the children to gather data on sociodemographic, lifestyle variables, and deworming status. Anthropometric measurements were taken for the height and weight of the children. Stool samples were collected and analyzed for STH infection using direct wet mount microscopy and the Kato-Katz technique. In multivariate logistic regression analysis, deworming within the past 6 months or 1 year was not significantly associated with underweight, stunting, and thinning. However, deworming within the past year was significantly associated with decreased weight-for-age z-score (adjusted mean difference = -0.245; 95% CI: -0.413 to -0.076; P = 0.004). Deworming in the past 6 months demonstrated a nonsignificant trend toward increased stunting (adjusted odds ratio = 1.258; 95% CI: 0.923-1.714; P = 0.145). This study provides evidence that deworming in the past 6 months or 1 year was not significantly associated with underweight, stunting, and thinning. However, deworming within the past year was associated with a significantly decreased weight-for-age z-score in young Ethiopian schoolchildren of Jimma Town after adjustment for confounding variables.

Effect of Deworming on Health Outcomes among Children Aged 12-59 Months in Tanzania: A Multilevel Mixed Effects Analysis

Introduction

Mass deworming of preschool children is a strategy suggested to prevent soil-transmitted helminth infections in most developing countries. Nonetheless, there is a scarcity of data showing the contribution of mass deworming to a child's nutritional status. The purpose of this study was to assess the effect of deworming on nutritional health outcomes (stunting, underweight, and anemia) in children aged 12 to 59 months.

Methods

A secondary analysis of data extracted from the Tanzania Demographic and Health Survey (TDHS) 2015-16 data was carried out. A total of 7,962 children were included in this study. A multilevel logistic regression was used at a 5% level of significance to determine the individual- and community-level determinants of deworming on health outcomes among children.

Results

The prevalence of underweight (62.6%), stunting (61.0%), and anemia (61.8%) was higher in children who were not dewormed than those who were dewormed. Female children were more likely to suffer from poor health outcomes (OR = 1.01 and 95% CI = 0.95-1.07) than male children. Children aged 24-35 months and 36-47 months were significantly less likely to suffer from poor health outcomes (OR = 0.89; 95% CI = 0.82-0.97 and OR = 0.88; 96% CI = 0.81-0.96, respectively; p < 0.01). Children from households with unimproved toilets (OR = 1.38 and 95% CI = 1.25-1.52), unimproved water sources (OR = 1.08 and 95% CI = 1.01-1.16), and living in rural areas (OR = 1.02 and 95% CI = 0.91-1.14) had higher odds for poor health outcomes.

Conclusion

Deworming may be an effective technique for preventing poor health outcomes in children and the risks associated with them, such as poor growth and development.

COVID-19 morbidity in lower versus higher income populations underscores the need to restore lost biodiversity of eukaryotic symbionts

The avoidance of infectious disease by widespread use of 'systems hygiene', defined by hygiene-enhancing technology such as sewage systems, water treatment facilities, and secure food storage containers, has led to a dramatic decrease in symbiotic helminths and protists in high-income human populations. Over a half-century of research has revealed that this 'biota alteration' leads to altered immune function and a propensity for chronic inflammatory diseases, including allergic, autoimmune and neuropsychiatric disorders. A recent Ethiopian study (EClinicalMedicine 39: 101054), validating predictions made by several laboratories, found that symbiotic helminths and protists were associated with a reduced risk of severe COVID-19 (adjusted odds ratio = 0.35; p<0.0001). Thus, it is now apparent that 'biome reconstitution', defined as the artificial re-introduction of benign, symbiotic helminths or protists into the ecosystem of the human body, is important not only for alleviation of chronic immune disease, but likely also for pandemic preparedness.

Interventions to improve water, sanitation, and hygiene for preventing soil-transmitted helminth infection

BACKGROUND

It is estimated that 1.5 billion people are infected with soil-transmitted helminths (STHs) worldwide. Re-infection occurs rapidly following deworming, and interruption of transmission is unlikely without complementary control efforts such as improvements in water, sanitation, and hygiene (WASH) access and behaviours.

OBJECTIVES

To assess the effectiveness of WASH interventions to prevent STH infection.

SEARCH METHODS

We used standard, extensive Cochrane search methods. The latest search date was 19 October 2021.

SELECTION CRITERIA

We included interventions to improve WASH access or practices in communities where STHs are endemic. We included randomized controlled trials (RCTs), as well as trials with an external control group where participants (or clusters) were allocated to different interventions using a non-random method (non-RCTs). We did not include observational study designs. Our primary outcome was prevalence of any STH infection. Prevalence of individual worms was a secondary outcome, including for Ascaris lumbricoides, Trichuris trichiura, hookworm (Ancylostoma duodenale or Necator americanus), or Strongyloides stercoralis. Intensity of infection, measured as a count of eggs per gram of faeces for each species, was another secondary outcome.

DATA COLLECTION AND ANALYSIS

Two review authors independently reviewed titles and abstracts and full-text records for eligibility, performed data extraction, and assessed risk of bias using the Cochrane risk of bias assessment tool for RCTs and the EPOC tool for non-RCTs. We used a random-effects meta-analysis to pool study estimates. We used Moran's I² statistic to assess heterogeneity and conducted subgroup analyses to explore sources of heterogeneity. We assessed the certainty of the evidence using the GRADE approach.

MAIN RESULTS

We included 32 studies (16 RCTs and 16 non-RCTs) involving a total of 52,944 participants in the review. Twenty-two studies (14 RCTs (16 estimates) and eight non-RCTs (11 estimates)) reported on our primary outcome, prevalence of infection with at least one STH species. Twenty-one studies reported on the prevalence of A lumbricoides (12 RCTs and 9 non-RCTs); 17 on the prevalence of T trichiura (9 RCTs and 8 non-RCTs); 18 on the prevalence of hookworm (10 RCTs and 8 non-RCTs); and one on the prevalence of S stercoralis (1 non-RCT). Sixteen studies measured the intensity of infection for an individual STH type. Ten RCTs and five non-RCTs reported on the intensity of infection of A lumbricoides; eight RCTs and five non-RCTs measured the intensity of infection of T trichiura; and eight RCTs and five non-RCTs measured the intensity of hookworm infection. No studies reported on the intensity of infection of S stercoralis. The overall pooled effect estimates showed that the WASH interventions under study may result in a slight reduction of any STH infection, with an odds ratio (OR) of 0.86 amongst RCTs (95% confidence interval (CI) 0.74 to 1.01; moderate-certainty evidence) and an OR of 0.71 amongst non-RCTs (95% CI 0.54 to 0.94; low-certainty evidence). All six of the meta-analyses assessing individual worm infection amongst both RCTs and non-RCTs had pooled estimates in the preventive direction, although all CIs encapsulated the null, leaving the possibility of the null or even harmful effects; the certainty of the evidence ranged from very low to moderate. Individual studies assessing intensity of infection showed mixed evidence supporting WASH. Subgroup analyses focusing on narrow specific subsets of water, sanitation, and hygiene interventions did very little to elucidate which interventions might be better than others. Data on intensity of infection (e.g. faecal egg count) were reported in a variety of ways across studies, precluding the pooling of results for this outcome. We did not find any studies reporting adverse events resulting from the WASH interventions under study or from mass drug administration (MDA).

AUTHORS' CONCLUSIONS

Whilst the available evidence suggests that the WASH interventions under study may slightly protect against STH infection, WASH also serves as a broad preventive measure for many other diseases that have a faecal oral transmission route of transmission. As many of the studies were done in addition to MDA/deworming (i.e. MDA was ongoing in both the intervention and control arm), our data support WHO recommendations for implementation of improvements to basic sanitation and adequate access to safe water alongside MDA. The biological plausibility for improved access to WASH to interrupt transmission of STHs is clear, but WASH interventions as currently delivered have shown impacts that were lower than expected. There is a need for more rigorous and targeted implementation research and process evaluations in order that future WASH interventions can better provide benefit to users. Inconsistent reporting of the intensity of infection underscores the need to define the minimal, standard data that should be collected globally on STHs to enable pooled analyses and comparisons.

Parental Self-Perception, Parental Investment, and Early Childhood Developmental Outcomes: Evidence From Rural China

Using a three-wave longitudinal survey conducted in 815 households in rural Western China, this study aims to examine the association between parental self-perception and early childhood development and the mediation effect of parental investment on the association between parental self-perception and child development when the sample children are at different ages in the early childhood (18-30, 22-36, and 49-65 months). The results demonstrate that parental self-perception are positively and significantly associated with child social-emotional development in all three ages of childhood (from 18 to 65 months). Positive and significant association between parental self-perception and child cognitive development is found in the ages from 22 to 65 months. In addition, findings of this study show that parental investment plays a mediating role in the association between parental self-perception and child cognitive development. The study calls on policymakers to help to strengthen parental self-perception and parental investment related to early childhood development, which should result in better child development in rural China.

Trajectories of child cognitive development during ages 0-3 in rural Western China: prevalence, risk factors and links to preschool-age cognition

BACKGROUND

Cognitive development after age three tends to be stable and can therefore predict cognitive skills in later childhood. However, there is evidence that cognitive development is less stable before age three. In rural China, research has found large shares of children under age three are developmentally delayed, yet little is known about the trajectories of cognitive development between 0 and 3 years of age or how developmental trajectories predict later cognitive skills. This study seeks to describe the trajectories of child cognitive development between the ages of 0-3 years and examine how different trajectories predict cognitive development at preschool age.

METHODS

We collected three waves of longitudinal panel data from 1245 children in rural Western China. Child cognitive development was measured by the Bayley Scales of Infant Development when the child was 6-12 months and 22-30 months, and by the Wechsler Preschool and Primary Scale of Intelligence-Fourth Edition when the child was 49-65 months. We used the two measures of cognitive development before age three to determine the trajectories of child cognitive development.

RESULTS

Of the children, 39% were never cognitively delayed; 13% were persistently delayed; 7% experienced improving cognitive development; and 41% experienced deteriorating development before age 3. Compared to children who had never experienced cognitive delay, children with persistent cognitive delay and those with deteriorating development before age 3 had significantly lower cognitive scores at preschool age. Children with improving development before age 3 showed similar levels of cognition at preschool age as children who had never experienced cognitive delay.

CONCLUSIONS

Large shares of children under age 3 in rural Western China show deteriorating cognitive development from infancy to toddlerhood, which predict lower levels of cognition at preschool age. Policymakers should invest in improving cognitive development before age 3 to prevent long-term poor cognition among China's rural children.

Prevalence, intensity and associated risk factors of soil-transmitted helminth and schistosome infections in Kenya: Impact assessment after five rounds of mass drug administration in Kenya

Background

In Kenya, over five million school age children (SAC) are estimated to be at risk of parasitic worms causing soil-transmitted helminthiasis (STH) and schistosomiasis. As such, the Government of Kenya launched a National School Based Deworming (NSBD) program in 2012 targeting the at-risk SAC living in endemic regions, with the aim of reducing infections prevalence to a level where they no longer constitute a public health problem. The impact of the program has been consistently monitored from 2012 to 2017 through a robust and extensive monitoring and evaluation (M&E) program. The aim of the current study was to evaluate the parasitological outcomes and additionally investigate water, sanitation and hygiene (WASH) related factors associated with infection prevalence after five rounds of mass drug administration (MDA), to inform the program’s next steps.

Materials and methods

We utilized a cross-sectional design in a representative, stratified, two-stage sample of school children across six regions in Kenya. A sample size of 100 schools with approximately 108 children per school was purposively selected based on the Year 5 STH infection endemicity prior to the survey. Stool samples were examined for the presence of STH and Schistosoma mansoni eggs using double-slide Kato-Katz technique, urine samples were processed using urine filtration technique for the presence of S. haematobium eggs. Survey questionnaires were administered to all the participating children to collect information on their demographic and individual, household and school level WASH characteristics.

Principal findings

Overall, STH prevalence was 12.9% (95%CI: 10.4–16.1) with species prevalence of 9.7% (95%CI: 7.5–12.6) for Ascaris lumbricoides, 3.6% (95%CI: 2.2–5.8) for Trichuris trichiura and 1.0% (95%CI: 0.6–1.5) for hookworm. S. mansoni prevalence was 2.2% (95%CI: 1.2–4.3) and S. haematobium prevalence was 0.3% (95%CI: 0.1–1.0). All the infections showed significant prevalence reductions when compared with the baseline prevalence, except S. mansoni. From multivariable analysis, increased odds of any STH infections were associated with not wearing shoes, adjusted odds ratio (aOR) = 1.36 (95%CI: 1.09–1.69); p = 0.007; high number of household members, aOR = 1.21 (95%CI: 1.04–1.41); p = 0.015; and school absenteeism of more than two days, aOR = 1.33 (95%CI: 1.01–1.80); p = 0.045. Further, children below five years had up to four times higher odds of getting STH infections, aOR = 4.68 (95%CI: 1.49–14.73); p = 0.008. However, no significant factors were identified for schistosomiasis, probably due to low prevalence levels affecting performance of statistical analysis.

Conclusions

After five rounds of MDA, the program shows low prevalence of STH and schistosomiasis, however, not to a level where the infections are not a public health problem. With considerable inter-county infection prevalence heterogeneity, the program should adopt future MDA frequencies based on the county’s infection prevalence status. Further, the program should encourage interventions aimed at improving coverage among preschool age children and improving WASH practices as long-term infection control strategies.

This paper presents the findings of an evaluation survey conducted in Year 6 of the Kenya National School-Based Deworming (NSBD) Program, following five years (2012–2017) of prior baseline and subsequent impact monitoring. The survey was conducted in 20 counties, covering six regions in Kenya. The survey showed continued and considerable reductions in prevalence over time, with most marked decline for hookworm, followed by Ascaris lumbricoides. Overall, the mass drug administration (MDA) program has driven both STH and schistosomiasis prevalence to relatively low levels, however not to a point where they no longer constitute a public health problem in Kenya. For these neglected tropical diseases (NTDs), and STH in particular, there are relatively few published examples of programmatic impact assessments enabling refined decisions regarding helminth control strategies. Kenya’s experiences in implementing, monitoring, and evaluating a high-coverage NSBD program are a continuing and increasingly important success story for the country, which provides learnings of importance for the international community.

"At three years of age, we can see the future": Cognitive skills and the life cycle of rural Chinese children

Background

While the Chinese education system has seen massive improvements over the past few decades, there still exists large academic achievement gaps between rural and urban areas, which threaten China's long-term development. Additionally, recent literature has underscored the importance of early childhood development (ECD) in later-life human capital development.

Objectives

We analyze the lifecycle of cognitive development and learning outcomes in rural Chinese children by first examining if ECD outcomes affect cognition levels, then seeing if cognitive delays persist as children grow, and finally exploring connections between cognition and education outcomes.

Methods

We combine data from four recent studies examining different age groups (0-3, 4-5, 10-11, 13-14) to track cognitive outcomes.

Results

First, we find that ECD outcomes for children in rural China are poor, with almost one-in-two children being cognitively delayed. Second, we find that these cognitive delays seem to persist into middle school, with almost 37% of rural junior high school students being cognitively delayed. Finally, we show that cognition has a close relationship to academic achievement.

Conclusion

Our results suggest that urban/rural gaps in academic achievement originate at least in part from differences in ECD outcomes.

Contributions

While many papers have analyzed ECD, human capital, and inequality separately, this is the first paper to explicitly connect and combine these topics to analyze the lifecycle of cognitive development in the context of rural China.

Interventions to improve disposal of child faeces for preventing diarrhoea and soil-transmitted helminth infection

BACKGROUND

Diarrhoea and soil-transmitted helminth (STH) infections represent a large disease burden worldwide, particularly in low-income countries. As the aetiological agents associated with diarrhoea and STHs are transmitted through faeces, the safe containment and management of human excreta has the potential to reduce exposure and disease. Child faeces may be an important source of exposure even among households with improved sanitation.

OBJECTIVES

To assess the effectiveness of interventions to improve the disposal of child faeces for preventing diarrhoea and STH infections.

SEARCH METHODS

We searched the Cochrane Infectious Diseases Group Specialized Register, CENTRAL, MEDLINE, Embase, and 10 other databases. We also searched relevant conference proceedings, contacted researchers, searched websites for organizations, and checked references from identified studies. The date of last search was 27 September 2018.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) and non-randomized controlled studies (NRS) that compared interventions aiming to improve the disposal of faeces of children aged below five years in order to decrease direct or indirect human contact with such faeces with no intervention or a different intervention in children and adults.

DATA COLLECTION AND ANALYSIS

Two review authors selected eligible studies, extracted data, and assessed the risk of bias. We used meta-analyses to estimate pooled measures of effect where appropriate, or described the study results narratively. We assessed the certainty of the evidence using the GRADE approach.

MAIN RESULTS

Sixty-three studies covering more than 222,800 participants met the inclusion criteria. Twenty-two studies were cluster RCTs, four were controlled before-and-after studies (CBA), and 37 were NRS (27 case-control studies (one that included seven study sites), three controlled cohort studies, and seven controlled cross-sectional studies). Most study sites (56/69) were in low- or lower middle-income settings. Among studies using experimental study designs, most interventions included child faeces disposal messages along with other health education messages or other water, sanitation, and hygiene (WASH) hardware and software components. Among observational studies, the main risk factors relevant to this review were safe disposal of faeces in the latrine or defecation of children under five years of age in a latrine.Education and hygiene promotion interventions, including child faeces disposal messages (no hardware provision)Four RCTs found that diarrhoea incidence was lower, reducing the risk by an estimated 30% in children under six years old (rate ratio 0.71, 95% confidence interval (CI) 0.59 to 0.86; 2 trials, low-certainty evidence). Diarrhoea prevalence measured in two other RCTs in children under five years of age was lower, but evidence was low-certainty (risk ratio (RR) 0.93, 95% CI 0.84 to 1.04; low-certainty evidence).Two controlled cohort studies that evaluated such an intervention in Bangladesh did not detect a difference on diarrhoea prevalence (RR 0.91, 95% CI 0.64 to 1.28; very low-certainty evidence). Two controlled cross-sectional studies that evaluated the Health Extension Package in Ethiopia were associated with a lower two-week diarrhoea prevalence in 'model' households than in 'non-model households' (odds ratio (OR) 0.26, 95% CI 0.16 to 0.42; very low-certainty evidence).Programmes to end open defecation by all (termed community-led total sanitation (CLTS) interventions plus adaptations)Four RCTs measured diarrhoea prevalence and did not detect an effect in children under five years of age (RR 0.92, 95% CI 0.79 to 1.07; moderate-certainty evidence). The analysis of two trials did not demonstrate an effect of the interventions on STH infection prevalence in children (pooled RR 1.03, 95% CI 0.64 to 1.65; low-certainty evidence).One controlled cross-sectional study compared the prevalence of STH infection in open defecation-free (ODF) villages that had received a CLTS intervention with control villages and reported a higher level of STH infection in the intervention villages (RR 2.51, 95% CI 1.74 to 3.62; very low-certainty evidence).Sanitation hardware and behaviour change interventions, that included child faeces disposal hardware and messagingTwo RCTs had mixed results, with no overall effect on diarrhoea prevalence demonstrated in the pooled analysis (RR 0.79, 95% CI 0.49 to 1.26; very low-certainty evidence).WASH hardware and education/behaviour change interventionsOne RCT did not demonstrate an effect on diarrhoea prevalence (RR 1.15, 95% CI 0.93 to 1.41; very low-certainty evidence).Two CBAs reported that the intervention reduced diarrhoea incidence by about a quarter in children under five years of age, but evidence was very low-certainty (rate ratio 0.77, 95% CI 0.71 to 0.84). Another CBA reported that the intervention reduced the prevalence of STH in an intervention village compared to a control village, again with GRADE assessed at very low-certainty (OR 0.17, 95% CI 0.02 to 0.73).Case-control studiesPooled results from case-control studies that presented data for child faeces disposal indicated that disposal of faeces in the latrine was associated with lower odds of diarrhoea among all ages (OR 0.73, 95% CI: 0.62 to 0.85; 23 comparisons; very low-certainty evidence). Pooled results from case-control studies that presented data for children defecating in the latrine indicated that children using the latrine was associated with lower odds of diarrhoea in all ages (OR 0.54, 95% CI 0.33 to 0.90; 7 studies; very low-certainty evidence).

AUTHORS' CONCLUSIONS

Evidence suggests that the safe disposal of child faeces may be effective in preventing diarrhoea. However, the evidence is limited and of low certainty. The limited research on STH infections provides only low and very-low certainty evidence around effects, which means there is currently no reliable evidence that interventions to improve safe disposal of child faeces are effective in preventing such STH infections.While child faeces may represent a source of exposure to young children, interventions generally only address it as part of a broader sanitation initiative. There is a need for RCTs and other rigorous studies to assess the effectiveness and sustainability of different hardware and software interventions to improve the safe disposal of faeces of children of different age groups.

Public health deworming programmes for soil-transmitted helminths in children living in endemic areas

BACKGROUND

The World Health Organization (WHO) recommends treating all school children at regular intervals with deworming drugs in areas where helminth infection is common. Global advocacy organizations claim routine deworming has substantive health and societal effects beyond the removal of worms. In this update of the 2015 edition we included six new trials, additional data from included trials, and addressed comments and criticisms.

OBJECTIVES

To summarize the effects of public health programmes to regularly treat all children with deworming drugs on child growth, haemoglobin, cognition, school attendance, school performance, physical fitness, and mortality.

SEARCH METHODS

We searched the Cochrane Infectious Diseases Group Specialized Register; Cochrane Central Register of Controlled Trials (CENTRAL); MEDLINE; Embase; LILACS; the metaRegister of Controlled Trials (mRCT); reference lists; and registers of ongoing and completed trials up to 19 September 2018.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) and quasi-RCTs that compared deworming drugs for soil-transmitted helminths (STHs) with placebo or no treatment in children aged 16 years or less, reporting on weight, height, haemoglobin, and formal tests of cognition. We also sought data on other measures of growth, school attendance, school performance, physical fitness, and mortality.

DATA COLLECTION AND ANALYSIS

At least two review authors independently assessed the trials for inclusion, risk of bias, and extracted data. We analysed continuous data using the mean difference (MD) with 95% confidence intervals (CIs). Where data were missing, we contacted trial authors. We stratified the analysis based on the background burden of STH infection. We used outcomes at time of longest follow-up. We assessed the certainty of the evidence using the GRADE approach.

MAIN RESULTS

We identified 51 trials, including 10 cluster-RCTs, that met the inclusion criteria. One trial evaluating mortality included over one million children, and the remaining 50 trials included a total of 84,336 participants. Twenty-four trials were in populations categorized as high burden, including nine trials in children selected because they were helminth-stool positive; 18 with intermediate burden; and nine as low burden.First or single dose of deworming drugsFourteen trials reported on weight after a single dose of deworming drugs (4970 participants, 14 RCTs). The effects were variable. There was little or no effect in studies conducted in low and intermediate worm burden groups. In the high-burden group, there was little or no effect in most studies, except for a large effect detected from one study area in Kenya reported in two trials carried out over 30 years ago. These trials result in qualitative heterogeneity and uncertainty in the meta-analysis across all studies (I² statistic = 90%), with GRADE assessment assessed as very low-certainty, which means we do not know if a first dose or single dose of deworming impacts on weight.For height, most studies showed little or no effect after a single dose, with one of the two trials in Kenya from 30 years ago showing a large average difference (2621 participants, 10 trials, low-certainty evidence). Single dose probably had no effect on average haemoglobin (MD 0.10 g/dL, 95% CI 0.03 lower to 0.22 higher; 1252 participants, five trials, moderate-certainty evidence), or on average cognition (1596 participants, five trials, low-certainty evidence). The data are insufficient to know if there is an effect on school attendance and performance (304 participants, one trial, low-certainty evidence), or on physical fitness (280 participants, three trials, very low-certainty evidence). No trials reported on mortality.Multiple doses of deworming drugsThe effect of regularly treating children with deworming drugs given every three to six months on weight was reported in 18 trials, with follow-up times of between six months and three years; there was little or no effect on average weight in all but two trials, irrespective of worm prevalence-intensity. The two trials with large average weight gain included one in the high burden area in Kenya carried out over 30 years ago, and one study from India in a low prevalence area where subsequent studies in the same area did not show an effect. This heterogeneity causes uncertainty in any meta-analysis (I² = 78%). Post-hoc analysis excluding trials published prior to 2000 gave an estimate of average difference in weight gain of 0.02 kg (95%CI from 0.04 kg loss to 0.08 gain, I² = 0%). Thus we conclude that we do not know if repeated doses of deworming drugs impact on average weight, with a fewer older studies showing large gains, and studies since 2000 showing little or no average gain.Regular treatment probably had little or no effect on the following parameters: average height (MD 0.02 cm higher, 95% CI 0.09 lower to 0.13 cm higher; 13,700 participants, 13 trials, moderate-certainty evidence); average haemoglobin (MD 0.01 g/dL lower; 95% CI 0.05 g/dL lower to 0.07 g/dL higher; 5498 participants, nine trials, moderate-certainty evidence); formal tests of cognition (35,394 participants, 8 trials, moderate-certainty evidence); school performance (34,967 participants, four trials, moderate-certainty evidence). The evidence assessing an effect on school attendance is inconsistent, and at risk of bias (mean attendance 2% higher, 95% CI 5% lower to 8% higher; 20,650 participants, three trials, very low-certainty evidence). No trials reported on physical fitness. No effect was shown on mortality (1,005,135 participants, three trials, low-certainty evidence).

AUTHORS' CONCLUSIONS

Public health programmes to regularly treat all children with deworming drugs do not appear to improve height, haemoglobin, cognition, school performance, or mortality. We do not know if there is an effect on school attendance, since the evidence is inconsistent and at risk of bias, and there is insufficient data on physical fitness. Studies conducted in two settings over 20 years ago showed large effects on weight gain, but this is not a finding in more recent, larger studies. We would caution against selecting only the evidence from these older studies as a rationale for contemporary mass treatment programmes as this ignores the recent studies that have not shown benefit.The conclusions of the 2015 edition have not changed in this update.

The long run impact of early childhood deworming on numeracy and literacy: Evidence from Uganda

BACKGROUND

Up to 1.45 billion people currently suffer from soil transmitted helminth infection, with the largest burden occurring in Africa and Asia. Safe and cost effective deworming treatment exists, but there is a debate about mass distribution of this treatment in high prevalence settings. While the World Health Organization recommends mass administration of anthelmintic drugs for preschool and school-aged children in high (>20%) prevalence settings, and several long run follow up studies of an influential trial have suggested large benefits that persist over time, recent systematic reviews have called this recommendation into question.

METHODS AND FINDINGS

This paper analyzes the long-term impact of a cluster-randomized trial in eastern Uganda that provided mass deworming treatment to preschool aged children from 2000 to 2003 on the numeracy and literacy skills of children and young adults living in those villages in 2010-2015. This study uses numeracy and literacy data collected seven to twelve years after the end of the deworming trial in a randomly selected subset of communities from the original trial, by an education-focused survey that had no relationship to the deworming study. Building on an earlier working paper which used data from 2010 and 2011 survey rounds, this paper uses an additional four years of numeracy and literacy data (2012, 2013, 2014, and 2015). Aggregating data from all survey rounds, the difference between numeracy scores in treatment versus control communities is 0.07 standard deviations (SD) (95% CI -0.10, 0.24, p = 0.40), the difference in literacy scores is 0.05 SD (95% CI -0.16, 0.27, p = 0.62), and the difference in total scores is 0.07 SD (95% CI -0.11, 0.25, p = 0.44). There are significant differences in program impact by gender, with numeracy and literacy differentially positively affected for girls, and by age, with treatment effects larger for the primary school aged subsample. There are also significant treatment interactions for those living in households with more treatment-eligible children. There is no evidence of differential treatment effects on age at program eligibility or number of years of program eligibility.

CONCLUSIONS

Mass deworming of preschool aged children in high prevalence communities in Uganda resulted in no statistically significant gains in numeracy or literacy 7-12 years after program completion. Point estimates were positive but imprecise; the study lacked sufficient power to rule out substantial positive effects or more modest negative effects. However, there is suggestive evidence that deworming was relatively more beneficial for girls, primary school aged children, and children living in households with other treated children.

RESEARCH APPROVAL

As this analysis was conducted on secondary data which is publicly available, no research approval was sought or received. All individual records were anonymized by the data provider prior to public release.

Deworming in non-pregnant adolescent girls and adult women: a systematic review and meta-analysis

BACKGROUND

The impact of deworming on parasite load, nutritional status and other health outcomes of non-pregnant adolescent girls and adult women is uncertain.

METHODS

MEDLINE, EMBASE, CINAHL, the Cochrane Central Register of Controlled Trials, the WHO International Clinical Trials Registry Platform, the Cochrane Database of Systematic Reviews and Food and Technology Abstracts databases were searched until 24 September 2018. Studies were included if they were randomised controlled trials (RCTs), controlled before and after studies or interrupted time studies comparing deworming with no intervention or placebo in non-pregnant adolescent girls and women 10 to 49 years old. Outcomes of interest included parasite load, reinfection, anaemia, severe anaemia, iron deficiency, diarrhoea or all-cause morbidity. Risk of bias was assessed using the Cochrane risk of bias tool.

RESULTS

We included four RCTs of mass deworming involving 1086 participants, in the analyses. Mass deworming probably reduces the prevalence of roundworm infection (RR 0.29; 95% CI 0.14 to 0.62; 2 trials; 1498 participants, moderate certainty evidence), prevalence of hookworm infection (RR 0.32; 95% CI 0.18 to 0.59; 2 trials; 1498 participants, moderate certainty evidence), prevalence of whipworm infection (RR 0.77; 95% CI 0.65 to 0.91; 2 trials; 1498 participants, moderate certainty evidence) compared to the control group. Deworming may make little or no difference in prevalence of anaemia (RR 0.82; 95% CI 0.60 to 1.11, 3 studies, 683 participants, low certainty evidence) and prevalence of iron-deficiency (RR 0.89; 95% CI 0.64 to 1.23, 1 study, 186 participants, low certainty evidence) compared to control. We are uncertain whether deworming reduces the prevalence of severe anaemia compared to control as the certainty of evidence was very low. None of the included studies assessed screen and treat deworming or reported reinfection, diarrhoea or adverse events.

CONCLUSIONS

Mass deworming probably reduces the prevalence of soil-transmitted helminth infections but may have little or no effect on anaemia and iron-deficiency in adolescent girls and non-pregnant women in comparison to no intervention or placebo. We are uncertain about the effect on severe anaemia. These results are limited by sparse data and the moderate to very low quality of evidence available.

SYSTEMATIC REVIEW REGISTRATION

The protocol was registered in PROSPERO (registration number: CRD42016039557 ).  Primary source of funding: Evidence and Programme Guidance unit, Department of Nutrition for Health and Development, World Health Organization (WHO).

Prospects for elimination of soil-transmitted helminths

Purpose of review

Soil-transmitted helminths (STH) are endemic in 120 countries and are associated with substantial morbidity and loss of economic productivity. Although current WHO guidelines focus on morbidity control through mass drug administration (MDA), there is global interest in whether a strategy targeting disease elimination might be feasible in some settings. This review summarizes the prospects for switching from control to an elimination strategy.

Recent findings

STH control efforts have reduced the intensity of infections in targeted populations with associated reductions in morbidity. However, adults are not frequently targeted and remain important reservoirs for reinfection of treated children. Recent modeling suggests that transmission interruption may be possible through expanded community-wide delivery of MDA, the feasibility of which has been demonstrated by other programs. However, these models suggest that high levels of coverage and compliance must be achieved. Potential challenges include the risk of prematurely dismantling STH programs and the potential increased risk of antihelminthic resistance.

Summary

Elimination of STH may offer an opportunity to eliminate substantial STH-related morbidity while reducing resource needs of neglected tropical disease programs. Evidence from large community trials is needed to determine the feasibility of interrupting the transmission of STH in some geographic settings.