Trichuris trichiura infection and cognition in children: results of a randomized clinical trial

Mass deworming for improving health and cognition of children in endemic helminth areas: A systematic review and individual participant data network meta-analysis

Background

Soil transmitted (or intestinal) helminths and schistosomes affect millions of children worldwide.

Objectives

To use individual participant data network meta-analysis (NMA) to explore the effects of different types and frequency of deworming drugs on anaemia, cognition and growth across potential effect modifiers.

Search Methods

We developed a search strategy with an information scientist to search MEDLINE, CINAHL, LILACS, Embase, the Cochrane Library, Econlit, Internet Documents in Economics Access Service (IDEAS), Public Affairs Information Service (PAIS), Social Services Abstracts, Global Health CABI and CAB Abstracts up to March 27, 2018. We also searched grey literature, websites, contacted authors and screened references of relevant systematic reviews.

Selection Criteria

We included randomised and quasirandomised deworming trials in children for deworming compared to placebo or other interventions with data on baseline infection.

Data Collection and Analysis

We conducted NMA with individual participant data (IPD), using a frequentist approach for random-effects NMA. The covariates were: age, sex, weight, height, haemoglobin and infection intensity. The effect estimate chosen was the mean difference for the continuous outcome of interest.

Results

We received data from 19 randomized controlled trials with 31,945 participants. Overall risk of bias was low. There were no statistically significant subgroup effects across any of the potential effect modifiers. However, analyses showed that there may be greater effects on weight for moderate to heavily infected children (very low certainty evidence).

Authors' Conclusions

This analysis reinforces the case against mass deworming at a population-level, finding little effect on nutritional status or cognition. However, children with heavier intensity infections may benefit more. We urge the global community to adopt calls to make data available in open repositories to facilitate IPD analyses such as this, which aim to assess effects for the most vulnerable individuals.

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.

Soil-transmitted helminth infection, loss of education and cognitive impairment in school-aged children: A systematic review and meta-analysis

BACKGROUND

Evidence of an adverse influence of soil transmitted helminth (STH) infections on cognitive function and educational loss is equivocal. Prior meta-analyses have focused on randomized controlled trials only and have not sufficiently explored the potential for disparate influence of STH infection by cognitive domain. We re-examine the hypothesis that STH infection is associated with cognitive deficit and educational loss using data from all primary epidemiologic studies published between 1992 and 2016.

METHODS

Medline, Biosis and Web of Science were searched for original studies published in the English language. Cognitive function was defined in four domains (learning, memory, reaction time and innate intelligence) and educational loss in two domains (attendance and scholastic achievement). Pooled effect across studies were calculated as standardized mean differences (SMD) to compare cognitive and educational measures for STH infected/non-dewormed children versus STH uninfected /dewormed children using Review Manager 5.3. Sub-group analyses were implemented by study design, risk of bias (ROB) and co-prevalence of Schistosoma species infection. Influential studies were excluded in sensitivity analysis to examine stability of pooled estimates.

FINDINGS

We included 36 studies of 12,920 children. STH infected/non-dewormed children had small to moderate deficits in three domains-learning, memory and intelligence (SMD: -0.44 to -0.27, P<0.01-0.03) compared to STH-uninfected/dewormed children. There were no differences by infection/treatment status for reaction time, school attendance and scholastic achievement (SMD: -0.26 to -0.16, P = 0.06-0.19). Heterogeneity of the pooled effects in all six domains was high (P<0.01; I2 = 66-99%). Application of outlier treatment reduced heterogeneity in learning domain (P = 0.12; I2 = 33%) and strengthened STH-related associations in all domains but intelligence (SMD: -0.20, P = 0.09). Results varied by study design and ROB. Among experimental intervention studies, there was no association between STH treatment and educational loss/performance in tests of memory, reaction time and innate intelligence (SMD: -0.27 to 0.17, P = 0.18-0.69). Infection-related deficits in learning persisted within design/ROB levels (SMD: -0.37 to -52, P<0.01) except for pre-vs post intervention design (n = 3 studies, SMD = -0.43, P = 0.47). Deficits in memory, reaction time and innate intelligence persisted within observational studies (SMD: -0.23 to -0.38, all P<0.01) and high ROB strata (SMD:-0.37 to -0.83, P = 0.07 to <0.01). Further, in Schistosoma infection co-prevalent settings, associations were generally stronger and statistically robust for STH-related deficits in learning, memory and reaction time tests(SMD:-0.36 to -0.55, P = 0.003-0.02). STH-related deficits in school attendance and scholastic achievement was noted in low (SMD:-0.57, P = 0.05) and high ROB strata respectively.

INTERPRETATION

We provide evidence of superior performance in five of six educational and cognitive domains assessed for STH uninfected/dewormed versus STH infected/not-dewormed school-aged children from helminth endemic regions. Cautious interpretation is warranted due to high ROB in some of the primary literature and high between study variability in most domains. Notwithstanding, this synthesis provides empirical support for a cognitive and educational benefit of deworming. The benefit of deworming will be enhanced by strategically employing, integrated interventions. Thus, multi-pronged inter-sectoral strategies that holistically address the environmental and structural roots of child cognitive impairment and educational loss in the developing world may be needed to fully realize the benefit of mass deworming programs.

Global Disability: Empowering Children of all Abilities

Worldwide, children are often not meeting their developmental potential owing to malnutrition, infection, lack of stimulation, and toxic stress. Children with disabilities are more likely to experience poverty, neglect, and abuse, and are less likely to have adequate access to education and medical care. Early childhood developmental stimulation can improve language, learning, and future participation in communities. Therapeutic supports and endeavors to reduce stigma for people of all abilities strengthen communities and allow for human thriving.

Measuring the Effect of Soil-Transmitted Helminth Infections on Cognitive Function in Children: Systematic Review and Critical Appraisal of Evidence

Recently the role of soil-transmitted helminth (STH) infections in children's cognitive developmental impairment has been under scrutiny. We conducted a systematic review of the evidence for associations between STH infections and cognitive function of children using the Preferred Reporting Items for Systematic Reviews and Meta-Analyses protocol. We aimed to identify the domains of cognitive function in three age strata (<24months, 24-59months and ≥60months) and critically appraise the general design protocol of the studies, with a focus on the cognitive function measurement tools used. A total of 42 papers fulfilled the inclusion criteria, including 10 studies from a recent Cochrane review. Our findings demonstrate variation in tested domains, lack of consistency in the use of measurement tools and analysis of results. Cognitive function measures in children aged under 59months have been mainly limited to domains of gross motor, fine motor and language skills, whereas in children aged 60months and above most studies tested domains such as memory and processing speed. Even within the same age group the results on the association between STH infections and measures of cognitive development were often conflicting. The current study highlights the need for methodological consensus in the use of measurement tools and data analysis protocols if the effect of STH infections on cognitive function domains in children is to be correctly established. This will be an imperative next step to generate conclusive evidence of the role of STH infections in cognitive development in children.

Effects of Health and Nutrition on Cognitive and Behavioural Development in Children in the First Three Years of Life: Part 2: Infections and Micronutrient Deficiencies: Iodine, Iron, and Zinc

The following paper and its accompanying paper (Grantham-McGregor SM, et al. Effects of health and nutrition on cognitive and behavioural development in children in the first three years of life. Part 1: Low birthweight, breastfeeding, and protein-energy malnutrition. Food Nutr Bull 1999;20:53–75) review the literature on the conditions that are prevalent and considered to be likely to affect child development and are therefore of public health importance. the reviews are selective, and we have generally focused on recent work, particularly in areas that remain controversial. the reviews are restricted to nutritional and health insults that are important in the first three years of life. Where possible, we have discussed the better studies. This paper considers the effects of infections and the major micronutrient deficiencies: iodine, iron, and zinc.

Deworming drugs for soil-transmitted intestinal worms in children: effects on nutritional indicators, haemoglobin, and school performance

BACKGROUND

The World Health Organization (WHO) recommends treating all school children at regular intervals with deworming drugs in areas where helminth infection is common. As the intervention is often claimed to have important health, nutrition, and societal effects beyond the removal of worms, we critically evaluated the evidence on benefits.

OBJECTIVES

To summarize the effects of giving deworming drugs to children to treat soil-transmitted helminths on weight, haemoglobin, and cognition; and the evidence of impact on physical well-being, school attendance, school performance, and mortality.

SEARCH METHODS

We searched the Cochrane Infectious Diseases Group Specialized Register (14 April 2015); Cochrane Central Register of Controlled Trials (CENTRAL), published in the Cochrane Library (2015, Issue 4); MEDLINE (2000 to 14 April 2015); EMBASE (2000 to 14 April 2015); LILACS (2000 to 14 April 2015); the metaRegister of Controlled Trials (mRCT); and reference lists, and registers of ongoing and completed trials up to 14 April 2015.

SELECTION CRITERIA

We included randomized controlled trials (RCTs) and quasi-RCTs comparing deworming drugs for soil-transmitted helminths with placebo or no treatment in children aged 16 years or less, reporting on weight, haemoglobin, and formal tests of intellectual development. We also sought data on school attendance, school performance, and mortality. We included trials that combined health education with deworming programmes.

DATA COLLECTION AND ANALYSIS

At least two review authors independently assessed the trials, evaluated 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 used outcomes at time of longest follow-up. The evidence quality was assessed using GRADE. This edition of the Cochrane Review adds the DEVTA trial from India, and draws on an independent analytical replication of a trial from Kenya.

MAIN RESULTS

We identified 45 trials, including nine cluster-RCTs, that met the inclusion criteria. One trial evaluating mortality included over one million children, and the remaining 44 trials included a total of 67,672 participants. Eight trials were in children known to be infected, and 37 trials were carried out in endemic areas, including areas of high (15 trials), moderate (12 trials), and low prevalence (10 trials). Treating children known to be infectedTreating children known to be infected with a single dose of deworming drugs (selected by screening, or living in areas where all children are infected) may increase weight gain over the next one to six months (627 participants, five trials, low quality evidence). The effect size varied across trials from an additional 0.2 kg gain to 1.3 kg. There is currently insufficient evidence to know whether treatment has additional effects on haemoglobin (247 participants, two trials, very low quality evidence); school attendance (0 trials); cognitive functioning (103 participants, two trials, very low quality evidence), or physical well-being (280 participants, three trials, very low quality evidence). Community deworming programmesTreating all children living in endemic areas with a dose of deworming drugs probably has little or no effect on average weight gain (MD 0.04 kg less, 95% CI 0.11 kg less to 0.04 kg more; trials 2719 participants, seven trials, moderate quality evidence), even in settings with high prevalence of infection (290 participants, two trials). A single dose also probably has no effect on average haemoglobin (MD 0.06 g/dL, 95% CI -0.05 lower to 0.17 higher; 1005 participants, three trials, moderate quality evidence), or average cognition (1361 participants, two trials, low quality evidence).Similiarly, regularly treating all children in endemic areas with deworming drugs, given every three to six months, may have little or no effect on average weight gain (MD 0.08 kg, 95% CI 0.11 kg less to 0.27 kg more; 38,392 participants, 10 trials, low quality evidence). The effects were variable across trials; one trial from a low prevalence setting carried out in 1995 found an increase in weight, but nine trials carried out since then found no effect, including five from moderate and high prevalence areas.There is also reasonable evidence that regular treatment probably has no effect on average height (MD 0.02 cm higher, 95% CI 0.14 lower to 0.17 cm higher; 7057 participants, seven trials, moderate quality evidence); average haemoglobin (MD 0.02 g/dL lower; 95% CI 0.08 g/dL lower to 0.04 g/dL higher; 3595 participants, seven trials, low quality evidence); formal tests of cognition (32,486 participants, five trials, moderate quality evidence); exam performance (32,659 participants, two trials, moderate quality evidence); or mortality (1,005,135 participants, three trials, low quality evidence). There is very limited evidence assessing an effect on school attendance and the findings are inconsistent, and at risk of bias (mean attendance 2% higher, 95% CI 4% lower to 8% higher; 20,243 participants, two trials, very low quality evidence).In a sensitivity analysis that only included trials with adequate allocation concealment, there was no evidence of any effect for the main outcomes.

AUTHORS' CONCLUSIONS

Treating children known to have worm infection may have some nutritional benefits for the individual. However, in mass treatment of all children in endemic areas, there is now substantial evidence that this does not improve average nutritional status, haemoglobin, cognition, school performance, or survival.

Effects of geohelminth infections on neurological development

Published reviews vary on the question of whether geohelminth infections affect cognitive development: some claim that the scarcity of evidence means that it is unlikely that they do; others present modest evidence for an effect; and others raise the possibility that the damage is considerable but largely unresearched. This chapter reviews the characteristics of the geohelminths themselves and the pathways by which they could affect the development of children in endemic areas. It describes the progress made in the last decade in conceptualizing children's brains as complex adaptive systems, with the suggestion that infections at different stages in brain development might have different neurobehavioral consequences. An examination of research reports and review articles highlights the difficulties inherent in assessing the effects of geohelminth infections: other serious obstacles to healthy development in the same population may mask the effects of the geohelminths, and consequently the intensity and pathogenicity of the infection is probably an important issue. Selecting cognitive measures suitable for assessing development in very young children is no simple matter, and careful statistical analysis is required to tease out the primary and secondary factors at work. The insights gained from a broad range of relevant research reports have placed us in a better position to conduct more telling research into the effects of these widespread, but neglected, tropical diseases.

Deworming drugs for soil-transmitted intestinal worms in children: effects on nutritional indicators, haemoglobin and school performance

BACKGROUND

The World Health Organization (WHO) recommends treating all school children at regular intervals with deworming drugs in areas where helminth infection is common. The WHO state this will improve nutritional status, haemoglobin, and cognition and thus will improve health, intellect, and school attendance. Consequently, it is claimed that school performance will improve, child mortality will decline, and economic productivity will increase. Given the important health and societal benefits attributed to this intervention, we sought to determine whether they are based on reliable evidence.

OBJECTIVES

To summarize the effects of giving deworming drugs to children to treat soil-transmitted intestinal worms (nematode geohelminths) on weight, haemoglobin, and cognition; and the evidence of impact on physical well being, school attendance, school performance, and mortality.

SEARCH METHODS

In February 2012, we searched the Cochrane Infectious Diseases Group Specialized Register, MEDLINE, EMBASE, LILACS, mRCT, and reference lists, and registers of ongoing and completed trials.

SELECTION CRITERIA

We selected randomized controlled trials (RCTs) and quasi-RCTs comparing deworming drugs for geohelminth worms with placebo or no treatment in children aged 16 years or less, reporting on weight, haemoglobin, and formal test of intellectual development. In cluster-RCTs treating communities or schools, we also sought data on school attendance, school performance, and mortality. We included trials that included health education with deworming.

DATA COLLECTION AND ANALYSIS

At least two authors independently assessed the trials, evaluated risk of bias, and extracted data. Continuous data were analysed using the mean difference (MD) with 95% confidence intervals (CI). Where data were missing, we contacted trial authors. We used GRADE to assess evidence quality, and this is reflected in the wording we used: high quality ("deworming improves...."); moderate quality ("deworming probably improves..."); low quality ("deworming may improve...."); and very low quality ("we don't know if deworming improves....").

MAIN RESULTS

We identified 42 trials, including eight cluster trials, that met the inclusion criteria. Excluding one trial where data are awaited, the 41 trials include 65,168 participants.Screening then treatingFor children known to be infected with worms (by screening), a single dose of deworming drugs may increase weight (0.58 kg, 95% CI 0.40 to 0.76, three trials, 139 participants; low quality evidence) and may increase haemoglobin (0.37 g/dL, 95% CI 0.1 to 0.64, two trials, 108 participants; low quality evidence), but we do not know if there is an effect on cognitive functioning (two trials, very low quality evidence).Single dose deworming for all childrenIn trials treating all children, a single dose of deworming drugs gave mixed effects on weight, with no effects evident in seven trials, but large effects in two (nine trials, 3058 participants, very low quality evidence). The two trials with a positive effect were from the same very high prevalence setting and may not be easily generalised elsewhere. Single dose deworming probably made little or no effect on haemoglobin (mean difference (MD) 0.06 g/dL, 95% CI -0.06 to 0.17, three trials, 1005 participants; moderate evidence), and may have little or no effect on cognition (two trials, low quality evidence).Mulitple dose deworming for all childrenOver the first year of follow up, multiple doses of deworming drugs given to all children may have little or no effect on weight (MD 0.06 kg, 95% CI -0.17 to 0.30; seven trials, 2460 participants; low quality evidence); haemoglobin, (mean 0.01 g/dL lower; 95% CI 0.14 lower to 0.13 higher; four trials, 807 participants; low quality evidence); cognition (three trials, 30,571 participants, low quality evidence); or school attendance (4% higher attendance; 95% CI -6 to 14; two trials, 30,243 participants; low quality evidence);For time periods beyond a year, there were five trials with weight measures. One cluster-RCT of 3712 children in a low prevalence area showed a large effect (average gain of 0.98 kg), whilst the other four trials did not show an effect, including a cluster-RCT of 27,995 children in a moderate prevalence area (five trials, 37,306 participants; low quality evidence). For height, we are uncertain whether there is an effect of deworming (-0.26 cm; 95% CI -0.84 to 0.31, three trials, 6652 participants; very low quality evidence). Deworming may have little or no effect on haemoglobin (0.00 g/dL, 95%CI -0.08 to 0.08, two trials, 1365 participants, low quality evidence); cognition (two trials, 3720 participants; moderate quality evidence). For school attendance, we are uncertain if there is an effect (mean attendance 5% higher, 95% CI -0.5 to 10.5, approximately 20,000 participants, very low quality evidence).Stratified analysis to seek subgroup effects into low, medium and high helminth endemicity areas did not demonstrate any pattern of effect. In a sensitivity analysis that only included trials with adequate allocation concealment, we detected no significant effects for any primary outcomes.One million children were randomized in a deworming trial from India with mortality as the primary outcome. This was completed in 2005 but the authors have not published the results.

AUTHORS' CONCLUSIONS

Screening children for intestinal helminths and then treating infected children appears promising, but the evidence base is small. Routine deworming drugs given to school children has been more extensively investigated, and has not shown benefit on weight in most studies, except for substantial weight changes in three trials conducted 15 years ago or more. Two of these trials were carried out in the same high prevalence setting. For haemoglobin and cognition, community deworming seems to have little or no effect, and the evidence in relation to school attendance, and school performance is generally poor, with no obvious or consistent effect. Our interpretation of this data is that it is probably misleading to justify contemporary deworming programmes based on evidence of consistent benefit on nutrition, haemoglobin, school attendance or school performance as there is simply insufficient reliable information to know whether this is so.

School food, politics and child health

OBJECTIVE

An analysis undertaken jointly in 2009 by the UN World Food Programme, The Partnership for Child Development and the World Bank was published as Rethinking School Feeding to provide guidance on how to develop and implement effective school feeding programmes as a productive safety net and as part of the efforts to achieve Education for All. The present paper reflects on how understanding of school feeding has changed since that analysis.

DESIGN

Data on school feeding programme outcomes were collected through a literature review. Regression models were used to analyse relationships between school feeding costs (from data that were collected), the per capita costs of primary education and Gross Domestic Product per capita. Data on the transition to national ownership, supply chains and country examples were collected through country case studies.

RESULTS

School feeding programmes increase school attendance, cognition and educational achievement, as well as provide a transfer of resources to households with possible benefits to local agricultural production and local market development. Low-income countries exhibit large variations in school feeding costs, with concomitant opportunities for cost containment. Countries are increasingly looking to transition from externally supported projects to national programmes.

CONCLUSIONS

School feeding is now clearly evident as a major social programme in most countries with a global turnover in excess of $US 100 billion. This argues for a continuing focus on the evidence base with a view to helping countries ensure that their programmes are as cost-effective as possible. Clear policy advice has never been more important.

Deworming drugs for soil-transmitted intestinal worms in children: effects on nutritional indicators, haemoglobin and school performance

BACKGROUND

The World Health Organization (WHO) recommends treating all school children at regular intervals with deworming drugs in areas where helminth infection is common. The WHO state this will improve nutritional status, haemoglobin, and cognition and thus will improve health, intellect, and school attendance. Consequently, it is claimed that school performance will improve, child mortality will decline, and economic productivity will increase. Given the important health and societal benefits attributed to this intervention, we sought to determine whether they are based on reliable evidence.

OBJECTIVES

To summarize the effects of giving deworming drugs to children to treat soil-transmitted intestinal worms (nematode geohelminths) on weight, haemoglobin, and cognition; and the evidence of impact on physical well being, school attendance, school performance, and mortality.

SEARCH METHODS

In February 2012, we searched the Cochrane Infectious Diseases Group Specialized Register, MEDLINE, EMBASE, LILACS, mRCT, and reference lists, and registers of ongoing and completed trials.

SELECTION CRITERIA

We selected randomized controlled trials (RCTs) and quasi-RCTs comparing deworming drugs for geohelminth worms with placebo or no treatment in children aged 16 years or less, reporting on weight, haemoglobin, and formal test of intellectual development. In cluster-RCTs treating communities or schools, we also sought data on school attendance, school performance, and mortality. We included trials that included health education with deworming.

DATA COLLECTION AND ANALYSIS

At least two authors independently assessed the trials, evaluated risk of bias, and extracted data. Continuous data were analysed using the mean difference (MD) with 95% confidence intervals (CI). Where data were missing, we contacted trial authors. We used GRADE to assess evidence quality, and this is reflected in the wording we used: high quality ("deworming improves...."); moderate quality ("deworming probably improves..."); low quality ("deworming may improve...."); and very low quality ("we don't know if deworming improves....").

MAIN RESULTS

We identified 42 trials, including eight cluster trials, that met the inclusion criteria. Excluding one trial where data are awaited, the 41 trials include 65,168 participants.For programmes that treat only children detected as infected (by screening), a single dose of deworming drugs probably increased weight (0.58 kg, 95% CI 0.40 to 0.76, three trials, 139 participants; moderate quality evidence) and may have increased haemoglobin (0.37 g/dL, 95% CI 0.1 to 0.64, two trials, 108 participants; low quality evidence), but we do not know if there is an effect on cognitive functioning (two trials, very low quality evidence).For a single dose of deworming drugs given to all children in endemic areas, there were mixed effects on weight, with no effects evident in seven trials, but large effects in two. Overall our analysis indicated that we are uncertain whether there was an effect on weight (nine trials, 3058 participants; very low quality evidence). For haemoglobin, deworming made little or no difference (0.02 g/dL, 95% CI -0.05 to 0.09, four trials, 1992 participants; low quality evidence), and we don't know if it improves cognition (one trial, very low quality evidence).For multiple doses of deworming drugs with follow up for up to one year given to all children in endemic areas, we are uncertain if there is an effect on weight (0.06 kg, 95% CI -0.17 to 0.30; seven trials, 2460 participants; very low quality evidence); cognition (three trials, very low quality evidence); or school attendance (4% higher attendance; 95% CI -6 to 14; two trials, 75 clusters and 143 individually randomized participants, very low quality evidence). For haemoglobin, the intervention may have little or no effect (mean 0.01 g/dL lower; 95% CI 0.14 lower to 0.13 higher; four trials, 807 participants; low quality evidence).For multiple doses of deworming drugs with follow up beyond one year given to all children in endemic areas there were five trials with weight measures. One cluster-RCT of 3712 children in a low prevalence area showed a large effect (average gain of 0.98kg), whilst the other four trials did not show an effect, including a cluster-RCT of 27,995 children in a moderate prevalence area. Overall, we are uncertain if there is an effect for weight (five trials, 302 clusters and 1045 individually randomized participants; very low quality evidence). For other outcomes, we are uncertain whether deworming affects height (-0.26 cm; 95%CI -0.84 to 0.31, three trials, 1219 participants); haemoglobin (0.02 g/dL, 95%CI 0.3 to 0.27, two trials, 1365 participants); cognition (two trials), or school attendance (mean attendance 5% higher, 95% CI -0.5 to 10.5, one trial, 50 clusters).Stratified analysis to seek subgroup effects into low, medium and high helminth endemicity areas did not demonstrate any pattern of effect. We did not detect any significant effects for any primary outcomes in a sensitivity analysis only including trials with adequate allocation concealment.One million children were randomized in a deworming trial from India with mortality as the primary outcome. This was completed in 2005 but the authors have not published the results.

AUTHORS' CONCLUSIONS

Screening children for intestinal helminths and then treating infected children appears promising, but the evidence base is small. Routine deworming drugs given to school children has been more extensively investigated, and has not shown benefit on weight in most studies, except for substantial weight changes in three trials conducted 15 years ago or more. Two of these trials were carried out in the same high prevalence setting. For haemoglobin, community deworming seems to have little or no effect, and the evidence in relation to cognition, school attendance, and school performance is generally poor, with no obvious or consistent effect. Our interpretation of this data is that it is probably misleading to justify contemporary deworming programmes based on evidence of consistent benefit on nutrition, haemoglobin, school attendance or school performance as there is simply insufficient reliable information to know whether this is so.

Developmental age, physical fitness andToxocaraseroprevalence amongst lower-secondary students living in rural areas contaminated withToxocaraeggs

Scarce and inconclusive information on general biological impact ofToxocarainvasion on paratenic hosts, and people in particular, has led us to undertake a comprehensive study of the problem. The study has been conducted in a rural environment, which is considered a toxocarosis risk factor. In total 200 soil samples have been screened forToxocaraeggs by flotation, of which 14·5% were positive. Backyards close to households were most heavily contaminated with infectious eggs – 21·7% of positive samples. ELISA serological tests performed on 242 lower-secondary students found 14·5% of the studied population to be definitely positive – 16·5% of boys and 12·8% of girls, respectively. The odds of being infected withToxocarawere 2 times (CI: 1·15–3·85) more likely for individuals who owned a cat than those who did not own a cat. Strong significant correlation between seropositivity and the presence of a dog in a household was found with boys. The level of developmental age was significantly higher in seropositive than in seronegative students. No significant correlation has been observed between the motor abilities and seropositivity of students. Seropositive boys had significantly lower end-of-year grades than their seronegative counterparts.

Semantic fluency: a sensitive marker for cognitive impairment in children with heavy diarrhea burdens?

One of the most affected cognitive impairments in children who experienced heavy burdens of diarrhea is semantic fluency, the same impairment that is most affected in Alzheimer's dementia. These findings are leading us into provocative genetic studies that may elucidate the evolution of such genetic polymorphisms as the APOE alleles. Alternatively, diarrhea could launch the cognitive deficits that might later progress in neurodegenerative diseases. In addition, they suggest that semantic fluency could provide a simple mean to assess cognitive impairment in impoverished settings so as to determine preventive measures.

Deworming drugs for treating soil-transmitted intestinal worms in children: effects on growth and school performance

BACKGROUND

In areas where intestinal worm infections occur, the World Health Organization recommends treating all school children at regular intervals with deworming drugs to improve growth and school performance. The evidence base for this policy needs to be established for countries to commit resources to implement these programmes.

OBJECTIVES

To summarize the effects of deworming drugs used to treat soil-transmitted intestinal worms (nematode geohelminths) on growth and school performance in children.

SEARCH STRATEGY

In May 2007, we searched the Cochrane Infectious Diseases Group Specialized Register, CENTRAL (The Cochrane Library 2007, Issue 2), MEDLINE, EMBASE, LILACS, mRCT, and reference lists.

SELECTION CRITERIA

Randomized and quasi-randomized controlled trials (RCTs) comparing deworming drugs for geohelminth worms with placebo or no treatment in children aged 16 years or less, reporting on growth, nutritional status, school performance, or cognition tests.

DATA COLLECTION AND ANALYSIS

Two authors independently assessed the trials and evaluated methodological quality; one author extracted data, and another checked a sample. Continuous data were analysed using the weighted mean difference (WMD) with 95% confidence intervals (CI). The random-effects model (RE model) was used in the presence of statistically significant heterogeneity.

MAIN RESULTS

Thirty-four RCTs, including six cluster-RCTs, met the inclusion criteria. Four trials had adequate allocation concealment, and three cluster-RCTs failed to take design effects into account in their analysis. Weight increased after one dose of a deworming drug (WMD 0.34 kg, 95% CI 0.05 to 0.64, RE model; 2448 children, 9 trials); however, there was considerable heterogeneity between trials that was not explained by background intestinal worm infection or intensity. A meta-analysis of multiple dose trials reporting on outcomes within a year of starting treatment showed no significant difference in weight gain (1714 children, 6 trials); however, one cluster-RCT did show effects on weight at one year in a subgroup analysis. In the seven multiple dose trials with follow up beyond 12 months, only one showed a significant increase in weight. Six of seven trials reported clear data on cognitive tests and school performance: five reported no significant effects, and one showed some improvements in three out of 10 cognitive tests.

AUTHORS' CONCLUSIONS

Deworming drugs used in targeted community programmes may be effective in relation to weight gain in some circumstances but not in others. No effect on cognition or school performance has been demonstrated.

WITHDRAWN: Anthelmintic drugs for treating worms in children: effects on growth and cognitive performance

BACKGROUND

In communities where helminth (worm) infections are common, they may contribute to poor nutritional status, anaemia, and impaired growth and learning in children. The World Health Organization, the World Bank and others recommend that children are routinely given deworming drugs in developing countries. This requires resources to deliver.

OBJECTIVES

To summarise the effects of anthelmintic drug treatment in children in relation to their growth and cognitive performance.

SEARCH STRATEGY

We searched the Cochrane Infectious Diseases Group Specialized Register (August 2004), CENTRAL) The Cochrane Library Issue 3, 2004), MEDLINE (1966 to August 2004), EMBASE (1980 to August 2004), and LILACS (August 2004). We contacted experts in the field.

SELECTION CRITERIA

Randomised and quasi-randomised trials of drug treatment compared with placebo or no drug treatment for intestinal helminths in children.

DATA COLLECTION AND ANALYSIS

Trial quality was assessed and data were extracted independently by two reviewers. Study authors were contacted for additional information.

MAIN RESULTS

Thirty trials involving more than 1500 children were included. There was potential for bias from inadequate concealment of allocation. Studies varied in relation to target groups, drugs administered and treatment regimens. Compared to placebo or no drug treatment, drug treatment for helminths was associated with some positive effects on change in weight, height and skinfold thickness. However there was significant heterogeneity between the results of the trials. There were some positive effects on mean weight change in the trials reporting this outcome; after a single dose (any anthelminth) the pooled estimate was 0.17 kg, (95% CI 0.10 to 0.25; fixed effects model assumed); and 0.38 kg (95% CI 0.00 to 0.77; random effects model assumed). Results from trials giving multiple doses showed mean weight change under one year of follow up of 0.10 kg (95% CI 0.04 to 0.17; fixed effects assumed); or 0.15 (95% CI 0.00 to 0.30; random effects assumed). At more than one year of follow up, mean weight change was 0.12 kg (95% CI -0.02 to 0.26; fixed effects assumed) and 0.43 (95% CI -0.61 to 1.47; random effects model assumed). Results from studies of cognitive performance were mixed and inconclusive.

AUTHORS' CONCLUSIONS

There is some limited evidence that routine treatment of children in areas where helminths are common has small effects on weight gain, but this is not consistent between trials. There is insufficient evidence to know whether this intervention improves cognitive performance. Our interpretation of these results is that the current public health programme investments in this intervention, based on the expectation that there will be an improvement in growth and learning, are not based on consistent or reliable evidence.

Impact of mass chemotherapy on the morbidity due to soil-transmitted nematodes

This review summarises current knowledge of the ill-effects of soil-transmitted helminthiasis and takes a detailed look at studies that have been published over the past decade describing the effect of mass anthelminthic use on the health of endemic communities. Mass chemotherapy appears to give maximal returns in terms of improved health in areas where hookworm is a major problem and albendazole is used regularly, along with iron supplements; in children it improves physical growth and iron stores, and in pregnant women it reduces the prevalence of iron-deficiency anaemia. In areas where ascariasis is common, the directly attributable benefits of chemotherapy may be minimal, but it can facilitate the entry of other health care programmes in children, because deworming for ascariasis is often much desired and appreciated by the community. In areas with Vitamin A deficiency and endemic ascariasis, Vitamin A supplementation can be combined with deworming: anthelminthics do not impair Vitamin A absorption but the worms may interfere with Vitamin A uptake by reducing fat absorption. Where trichuriasis is a major problem, single dose chemotherapy may take some time to reduce prevalence, but reduction of heavy infections will reduce the incidence of Trichuris Dysentery Syndrome, probably benefit the learning abilities of affected schoolchildren, and may reduce anaemia and stunting. In general, children should be treated as early as possible, and in areas of very high prevalence, thrice-yearly mass chemotherapy probably improves health better than twice-yearly treatment.

Genetic component to susceptibility to Trichuris trichiura: evidence from two Asian populations

Trichuris trichiura is an helminthic infection with potentially severe health consequences. The hypothesis that host genetic factors can account for the distribution of Trichuris was tested using familial data on egg counts available for two populations, the Jirels of Nepal and the population of Jishan Island in Jiangxi Province of the People's Republic of China. Whipworm is highly prevalent in the Jishan Island population (86%), but occurs at a low rate in the Jirel population (14%). A quantitative genetic analysis was performed on each data set, using a variance component approach. Approximately 28% of the variation in Trichuris trichiura loads was attributable to genetic factors in both populations. Common household effects accounted for only 4% of the variation in the Jirels and none of the variation in the Jishan Island population. These concordant results from two separate populations provide strong evidence of the important role of genetics in determining differential susceptibility to whipworm infection.

Heavy schistosomiasis associated with poor short-term memory and slower reaction times in Tanzanian schoolchildren

Cross-sectional studies of the relationship between helminth infection and cognitive function can be informative in ways that treatment studies cannot. However, interpretation of results of many previous studies has been complicated by the failure to control for many potentially confounding variables. We gave Tanzanian schoolchildren aged 9-14 a battery of 11 cognitive and three educational tests and assessed their level of helminth infection. We also took measurements of an extensive range of potentially confounding or mediating factors such as socioeconomic and educational factors, anthropometric and other biomedical measures. A total of 272 children were moderately or heavily infected with Schistosoma haematobium, hookworm or both helminth species and 117 were uninfected with either species. Multiple regression analyses, controlling for all confounding and mediating variables, revealed that children with a heavy S. haematobium infection had significantly lower scores than uninfected children on two tests of verbal short-term memory and two reaction time tasks. In one of these tests the effect was greatest for children with poor nutritional status. There was no association between infection and educational achievement, nor between moderate infection with either species of helminth and performance on the cognitive tests. We conclude that children with heavy worm burdens and poor nutritional status are most likely to suffer cognitive impairment, and the domains of verbal short-term memory and speed of information processing are those most likely to be affected.

Effects of iron supplementation and anthelmintic treatment on motor and language development of preschool children in Zanzibar: double blind, placebo controlled study

OBJECTIVE

To measure the effects of iron supplementation and anthelmintic treatment on iron status, anaemia, growth, morbidity, and development of children aged 6-59 months.

DESIGN

Double blind, placebo controlled randomised factorial trial of iron supplementation and anthelmintic treatment.

SETTING

Community in Pemba Island, Zanzibar.

PARTICIPANTS

614 preschool children aged 6-59 months.

MAIN OUTCOME MEASURES

Development of language and motor skills assessed by parental interview before and after treatment in age appropriate subgroups.

RESULTS

Before intervention, anaemia was prevalent and severe, and geohelminth infections were prevalent and light-Plasmodium falciparum infection was nearly universal. Iron supplementation significantly improved iron status, but not haemoglobin status. Iron supplementation improved language development by 0.8 (95% confidence interval 0.2 to 1.4) points on the 20 point scale. Iron supplementation also improved motor development, but this effect was modified by baseline haemoglobin concentrations (P=0.015 for interaction term) and was apparent only in children with baseline haemoglobin concentrations <90 g/l. In children with a baseline haemoglobin concentration of 68 g/l (one standard deviation below the mean value), iron treatment increased scores by 1.1 (0.1 to 2.1) points on the 18 point motor scale. Mebendazole significantly reduced the number and severity of infections caused by Ascaris lumbricoides and Trichuris trichiura, but not by hookworms. Mebendazole increased development scores by 0.4 (-0.3 to 1.1) points on the motor scale and 0.3 (-0.3 to 0.9) points on the language scale.

CONCLUSIONS

Iron supplementation improved motor and language development of preschool children in rural Africa. The effects of iron on motor development were limited to children with more severe anaemia (baseline haemoglobin concentration <90 g/l). Mebendazole had a positive effect on motor and language development, but this was not statistically significant.

Multiple helminth infections in children: impact and control

Parasitic worm infections are amongst the most widespread of all chronic human infections. It is estimated that there are more than 3 billion infections in the world today. In many low income countries it is often more common to be infected than not to be. Indeed, a child growing up in an endemic community can expect be infected soon after weaning, and to be infected and constantly reinfected for the rest of her or his life. Infection is most common amongst the poorest and most disadvantaged communities, and is typically most intense in children of school going age. As the risk of morbidity is directly related to intensity of infection, it follows that children are the most at risk from the morbid effects of disease. Multiparasite infections are also common in such communities and there is evidence that individuals harbouring such infections may suffer exacerbated morbidity, making children even more vulnerable. Thus, these infections pose a serious threat to the health and development of children in low income countries. For many years, the need to control these infections has lain uncontested, and with the advent of broad-spectrum anthelminthic drugs that are cheap, safe and simple to deliver, control has at last become a viable option for many communities. Furthermore, there is now increased emphasis being placed on a multispecies approach as a cost-effective mechanism to control the morbidity of virtually all the major helminthic infections of humans.

Effects of treatment for intestinal helminth infection on growth and cognitive performance in children: systematic review of randomised trials

OBJECTIVE

To summarise the effects of anthelmintic drug treatment on growth and cognitive performance in children.

DATA SOURCES

Electronic databases: Cochrane Infectious Diseases Group controlled trial register, Cochrane controlled trials register, Embase, and Medline. Citations of all identified trials. Contact with the World Health Organization and field researchers.

REVIEW METHODS

Systematic review of randomised controlled trials in children aged 1-16 that compared anthelmintic treatment with placebo or no treatment. Assessment of validity and data abstraction conducted independently by two reviewers.

MAIN OUTCOME MEASURES

Growth and cognitive performance.

RESULTS

Thirty randomised controlled trials in more than 15 000 children were identified. Effects on mean weight were unremarkable, and heterogeneity was evident in the results. There were some positive effects on mean weight change in the trials reporting this outcome: after a single dose (any anthelmintic) the pooled estimates were 0.24 kg (95% confidence interval 0.15 kg to 0. 32 kg; fixed effects model assumed) and 0.38 kg (0.01 kg to 0.77 kg; random effects model assumed). Results from trials of multiple doses showed mean weight change in up to one year of follow up of 0.10 kg (0.04 kg to 0.17 kg; fixed effects) or 0.15 kg (0.00 to 0.30; random effects). At more than one year of follow up, mean weight change was 0.12 kg (-0.02 kg to 0.26 kg; fixed effects) and 0.43 (-0.61 to 1. 47; random effects). Results from studies of cognitive performance were inconclusive.

CONCLUSIONS

There is some limited evidence that routine treatment of children in areas where helminths are common has effects on weight gain, but this is not consistent between trials. There is insufficient evidence as to whether this intervention improves cognitive performance.

Evidence for an association between hookworm infection and cognitive function in Indonesian school children

The association between helminth infection and cognitive and motor function was investigated in school-age children in Java, Indonesia. 432 children from 42 primary schools participated in the study. Children were stratified by age and sex into two age groups, 8-9 years and 11-13 years. Children infected with hookworm performed significantly worse than children without hookworm infection in 6 of the 14 cognitive or motor tests. After controlling for school (as a random effect) plus age, socio-economic status and parental education, sex, stunting (height-for-age < - 2sd), body mass index, haemoglobin concentration and the presence of A. lumbricoides and T. trichiura infections, infection with hookworm explained significantly lower scores on tests of Fluency (P < 0.01), Digit-Span Forwards (P < 0.01), Number Choice (P < 0.01), Picture Search (P < 0.03), Stroop Colour Word (P < 0.02) and Mazes (P < 0.001). In 4 of the 6-tests (Fluency, Number Choice, Picture Search and Mazes), there was a significant interaction between hookworm infection and age (P < 0.03), indicating that the association between hookworm and lower test scores increased with age. No associations were observed between hookworm infection and scores in tests of Digit-Span Backwards, Corsi-Block, Stroop Colour, Stroop Interference, Free Recall, Verbal Analogies, Bead Threading or the Pegboard (P > 0.05). Tests associated with helminths represented various functions of working memory. No significant associations between helminth infection and motor function were observed that could not be explained by chance. The results suggest that hookworm infection can have a significant adverse effect on children's working memory which may have consequences for a child's reasoning ability and reading comprehension. Although the results are only associational, the fact that differences in cognition were observed at baseline imply that preventing infection with helminths in school-age children could be of benefit.

A healthy body and a healthy mind?: the relationship between ill-health and cognitive function in school-age children

Health of school age children and the Partnership for Child Development

Until recently, health programmes in developing countries have focused on infant survival and on the health of adolescents and, consequently, the health concerns of children of school age, falling between the ages of infancy and adolescence, have been neglected. The World Bank Development Report of 1993, stated a need to move beyond the focus on survival and to capture the concept that community health depends on the quality of life and opportunities for development. In response, the Partnership for Child Development was set up in 1992 to address the problem of ill-health among school-age children in the developing world.

Enterobius, trichuris, capillaria, and hookworm including ancylostoma caninum

Infections by the nematodes Enterobius, Trichuris, Capillaria, and hookworm are some of the most widespread gastrointestinal infections worldwide. This article is designed not only to provide an overview of the different parasites in terms of epidemiology, clinical manifestation, and disease but also to highlight particular areas of intensive research activity that are providing new insights into both the biology of the host-parasite relationship and possible new approaches to infection management for the future.

Trichuris trichiura infection and cognitive function in Jamaican school children

Trichuris trichiura is extremely prevalent worldwide and there is concern that this geohelminth may affect the cognitive function of children in developing countries. A random-controlled, double-blind, treatment trial was conducted in Jamaican children with light to moderate infections. This was part of a research programme involving several studies in Jamaica. Ninety-seven subjects, each with a minimum of 1200 T. trichiura eggs/g faeces, were randomly assigned to placebo (N = 48) or treatment (N = 49) groups. Each pair of infected children was matched with an uninfected classmate (N = 48). All children were given seven cognitive function tests: French-learning; digit spans (forwards and backwards), Corsi block span; fluency; picture search; and silly sentences. Albendazole was given to the treatment group and the other groups received a placebo. Three months later, these treatments were repeated, and the cognitive function battery was given again. On pre-test, the infected groups performed significantly poorer only in the silly-sentence test (analysis of variance F-value = 8.17; two degrees of freedom; P < 0.001). There was no significant improvement with treatment in any of the tests. Taking into account these findings and those of the other Jamaican studies, it is therefore probable that light to moderate Trichuris infections have little effect on cognitive functioning in school children who have adequate nutritional status.