How much evidence do we have that mass deworming of children really has much of an impact?

  • joeturner
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Re: How much evidence do we have that mass deworming of children really has much of an impact?

Another interesting paper out today on this subject in the open-access journal PLOS ONE:

The Effect of Deworming on Growth in One-Year-Old Children Living in a Soil-Transmitted Helminth-Endemic Area of Peru: A Randomized Controlled Trial


by Serene A. Joseph, Martín Casapía, Antonio Montresor and others

journals.plos.org/plosntds/article?id=10...journal.pntd.0004020

This was a fully randomised study in Peru where they were studying the effects of a single dose of mebendazole on very young (1 year old) children.

The summary of conclusions reads:

Overall, with one year of follow-up, no effect of deworming on growth could be detected in this population of preschool-age children. Low baseline STH prevalence and intensity and/or access to deworming drugs outside of the trial may have diluted the potential effect of the intervention.


So it seems that the basic results suggest no effect of the deworming medication on this population of infants, but the researchers are suggesting possible reasons why not, including other access to deworming medication outside of the trial.

Also, perhaps, school-aged children are more susceptible or the infants for some reason do not respond to the medication.
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Re: How much evidence do we have that mass deworming of children really has much of an impact?

This paper tried to examine why the mass deworming programme in Kenya was more effective in some places than others:

Understanding Heterogeneity in the Impact of National Neglected Tropical Disease Control Programmes: Evidence from School-Based Deworming in Kenya

by Birgit Nikolay, Charles S. Mwandawiro, Jimmy H. Kihara and others

journals.plos.org/plosntds/article?id=10...journal.pntd.0004108

The headline seems to be that

Greater reductions in hookworm prevalence were associated with high community level access to improved sanitation, as well as county economy and health service delivery indicator scores.


Perhaps unsurprisingly given reinfection rates, deworming was more effective in schools which had better WASH, socioeconomic and other benefits.

Which, in my opinion, underlines the point that deworming programmes cannot be effective without also considering sanitation provision.
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  • muench
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Re: How much evidence do we have that mass deworming of children really has much of an impact?

(for novice users please note this discussion thread already spans over three pages; access the other pages at the bottom of this thread).

Following on from that Cochrane review earlier in this thread, another review analysis was published recently. Joe Turner brought it to my attention on twitter and I am impressed that it's already been added to the Wikipedia article on mass deworming with this summary sentence:

A 2017 review reanalyzed available studies and concluded that mass deworming for soil-transmitted helminths with or without deworming for schistosomiasis had little effect but for schistosomiasis, mass deworming might be effective for weight but is probably ineffective for height, cognition, and attendance.[23]


See here:
en.wikipedia.org/wiki/Mass_deworming#Evidence

The paper itself (open access) is here:
www.thelancet.com/journals/langlo/articl...(16)30242-X/abstract

Title:
Mass deworming to improve developmental health and wellbeing of children in low-income and middle-income countries: a systematic review and network meta-analysis

Abstract:

Background
Soil-transmitted helminthiasis and schistosomiasis, considered among the neglected tropical diseases by WHO, affect more than a third of the world's population, with varying intensity of infection. We aimed to evaluate the effects of mass deworming for soil-transmitted helminths (with or without deworming for schistosomiasis or co-interventions) on growth, educational achievement, cognition, school attendance, quality of life, and adverse effects in children in endemic helminth areas.

Methods
We searched 11 databases up to Jan 14, 2016, websites and trial registers, contacted authors, and reviewed reference lists. We included studies published in any language of children aged 6 months to 16 years, with mass deworming for soil-transmitted helminths or schistosomiasis (alone or in combination with other interventions) for 4 months or longer, that reported the primary outcomes of interest. We included randomised and quasi-randomised trials, controlled before–after studies, interrupted time series, and quasi-experimental studies. We screened in duplicate, then extracted data and appraised risk of bias in duplicate with a pre-tested form. We conducted random-effects meta-analysis and Bayesian network meta-analysis.

Findings
We included 52 studies of duration 5 years or less with 1 108 541 children, and four long-term studies 8–10 years after mass deworming programmes with more than 160 000 children. Overall risk of bias was moderate. Mass deworming for soil-transmitted helminths compared with controls led to little to no improvement in weight over a period of about 12 months (0·99 kg, 95% credible interval [CrI] −0·09 to 0·28; moderate certainty evidence) or height (0·07 cm, 95% CrI −0·10 to 0·24; moderate certainty evidence), little to no difference in proportion stunted (eight fewer per 1000 children, 95% CrI −48 to 32; high certainty evidence), cognition measured by short-term attention (−0·23 points on a 100 point scale, 95% CI −0·56 to 0·14; high certainty evidence), school attendance (1% higher, 95% CI −1 to 3; high certainty evidence), or mortality (one fewer per 1000 children, 95% CI −3 to 1; high certainty evidence). We found no data on quality of life and little evidence of adverse effects. Mass deworming for schistosomiasis might slightly increase weight (0·41 kg, 95% CrI −0·20 to 0·91) and has little to no effect on height (low certainty evidence) and cognition (moderate certainty evidence). Our analyses do not suggest indirect benefits for untreated children from being exposed to treated children in the community. We are uncertain about effects on long-term economic productivity (hours worked), cognition, literacy, and school enrolment owing to very low certainty evidence. Results were consistent across sensitivity and subgroup analyses by age, worm prevalence, baseline nutritional status, infection status, impact on worms, infection intensity, types of worms (ascaris, hookworm, or trichuris), risk of bias, cluster versus individual trials, compliance, and attrition.

Interpretation
Mass deworming for soil-transmitted helminths with or without deworming for schistosomiasis had little effect. For schistosomiasis, mass deworming might be effective for weight but is probably ineffective for height, cognition, and attendance. Future research should assess which subset of children do benefit from mass deworming, if any, using individual participant data meta-analysis.

Funding
Canadian Institutes of Health Research and WHO.


The paper mentions sanitation 5 times, and I like e.g. this sentence where sanitation is mentioned:

These policy options include the need for investment in interventions to address basic determinants of worm infestations such as poverty, living conditions, sanitation, and inequities. Decisions on public health approaches in such settings need to be taken on the basis of human rights, ethics, and evidence-based, sustainable cost-effective approaches.


If you follow Joe Turner on twitter ( twitter.com/bucksci ) you would have seen a twitter discussion that followed his post.
First between him and I:

Joe Turner ‏@bucksci 11. Dez.
@EvMuench I think it just shows deworming without sanitation is ineffective.

Elisabeth von Muench ‏@EvMuench 11. Dez.
@bucksci Sounds good but does the review prove beyond doubt that #deworming WITH #sanitation IS effective?

Joe Turner ‏@bucksci 11. Dez.
@EvMuench sadly the only other option is believing that deworming doesn't work AT ALL.

Elisabeth von Muench ‏@EvMuench 11. Dez.
@bucksci which would be counter-intuitive... After all, why else would we deworm e.g. pets. Perhaps diff. is mass deworming vs. individual

Joe Turner ‏@bucksci 11. Dez.
@EvMuench right. Mass deworming progs - widely believed to be cheapest and most effective of almost any interv - don't work. Mindblowing.

Later he had another quite heated discussion with another twitter user ( twitter.com/callmekaeti ) who disagreed with the Cochrane reviews and said:

Kaeti
‏@callmekaeti
@bucksci @EvMuench Notable quote: The conclusion may contain the reviewer’s biases & may cast a shadow on credibility of the whole review


‏@callmekaeti
@bucksci @EvMuench or: The hypothesis of common zero effect of multiple-dose MDA deworming on child weight at longest follow-up is rejected

so this other twitter user (whom I don't know) also mentioned another study which comes to an opposing result. This is now summarised in the Wikipedia article like this:

A 2016 review focused on the effects of deworming on child weight included studies omitted from Cochrane, and extracted additional data from included studies. The review concluded that in environments with greater than 20% prevalence, where the WHO recommends mass treatment, the estimated average weight gain per dollar expenditure from deworming MDA is more than 35 times that estimated from school feeding programs.[22]


Paper [22] (not yet peer reviewed) is this:
www.nber.org/papers/w22382


Overall it seems to be really difficult to do really good solid studies on this matter, and then even harder when reviews of those (weak?) studies come to certain conclusions.

It seems to be a topic hotly debated amongst proponents and opponents of mass deworming.

I am only a layperson on this topic myself. My gut feeling has been if mass deworming is so cheap and if it has no detrimental side then just do it, even if the evidence is not 100% clear yet (after all, would you want YOUR child to walk around with worms in its intestines??). However, I have also always thought shouldn't we focus more on preventing infection in the first place, i.e. toilets and hygiene? Perhaps the "easy way out" of just distributing pills to all children has been less effective than we have thought? After all, looking at children in developed countries, they don't have to take deworming tablets, so that should be what we're striving for, shouildn't it?

Does anyone know about programs where mass deworming has been combined with "mass toilet use", behavior change and hygiene programs? That would be the ideal case (but far more expensive than mass deworming alone!).

Looking forward to hearing more about this topic.

Regards,
Elisabeth

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  • sayboom
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Re: How much evidence do we have that mass deworming of children really has much of an impact?

Regarding the deworming study in Kenya, it is important to note that it concluded that it improved school participation, and that is it. In other words, attendance increased, but the article makes no claim (nor did the authors measure) that there were any other educational outcomes we might find important (such as kids actually learning more, performing better in tests, or whatever indicator of school performance you'd want to use, apart from school attendance).

Senior Program Officer on the Water, Sanitation and Hygiene team
Bill & Melinda Gates Foundation, Seattle, WA, USA
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Re: How much evidence do we have that mass deworming of children really has much of an impact?

Dear Jan Willem,*

Welcome to the Forum! Deworming is such an important (and hot) topic, therefore I am glad you posted about it.

I would like to take the opportunity to ask you if you could say a bit about grants of the Bill & Melinda Gates Foundation that include deworming interventions? How do the grants on deworming programs link with the Water, Sanitation, Hygiene programs (if they do)? I assume the deworming programs sit with your global health division whereas you are in the global development division, so it might be difficult to work across programs?

By the way, regarding measuring factors that influence school participation, we also had an in-depth discussion about it in this thread where we pondered whether providing improved menstrual hygiene and school toilets are proven interventions to "keep girls in school longer". The conclusion was that it is not so easy to prove or disprove this theory as there are so many factors which determine if a girl child can stay in school or drops out (or has many absentee days). See here (2 pages): forum.susana.org/component/kunena/24-men...rwise-on-absenteeism

Regards,
Elisabeth

+++++++++++

Some more background information on grants by the Gates Foundation:
There is quite a good Wikipedia page about the Gates Foundation:
en.wikipedia.org/wiki/Bill_%26_Melinda_Gates_Foundation
There is a section in there where another Wikipedian added a table showing funding streams to different categories which is quite interesting:
en.wikipedia.org/wiki/Bill_%26_Melinda_G...developing_countries (with a short discussion on the talk page here: en.wikipedia.org/wiki/Talk:Bill_%26_Meli...out_funds_for_grants )

I guess deworming programs would fall under Infectious disease control which is the biggest chunk of funding for the period 2009-2015.


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  • Tore
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Re: How much evidence do we have that mass deworming of children really has much of an impact?

De-worming will have minimal long term affect if proper sanitation is not implemented at the same time. The worms in the individuals discharge thousands of eggs daily that will survive from days to years depending on the environmental conditions. if you de-worm and don't put the feces in proper sanitation facilities where the eggs cannot infect the individuals then the the eggs will infect the de-wormed individuals and infections will continue. If proper sanitation is provided at the same time as the de-worming then you will still need to have additional de-worming until all eggs and worms that can come in contact with the individuals are eliminated by using proper sanitation.

Sanitation & water consultant in developing countries
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