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

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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.
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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.


* If you are a forum reader and wonder how one forum member can know what the name and affiliation of another forum member, then here is the answer: you just need to click on the person's login name above their photo. If you are logged in, you can then see their name and full profile. And if you click on the little globe icon below their photo, you can see the website that they linked to.
Dr. Elisabeth von Muench
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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?

(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
Dr. Elisabeth von Muench
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  • joeturner
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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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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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  • Elisabeth
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Re: How much evidence do we have that mass deworming of children really has much of an impact?

Dear Marijn,

You wrote:

As I have mentioned a few times before, I also wonder how many of these helminth infections are caused by a lack of animal manure management.


I think animal manure is only part of the life cycle of a few of the helminths but not of Ascaris for example whose eggs are in the human feces (not the animal feces, I think).
The number of all the different helminth types and their complicated life cycles is mind boggling...

With some helminths, humans get infected by eating raw or undercooked pork or beef if the animal was infected. For example Taeniasis is spread like this:
en.wikipedia.org/wiki/Taeniasis

Taeniasis is contracted after eating undercooked or raw pork and beef that contain the larvae. Cysticercosis occurs after ingestion of contaminated food, water, or soil that contain T. solium eggs.[14][15]


My general impression from reading about helminths is that as far as feces go, human feces are more dangerous for re-infection with helminths than animal faeces.
But I might be wrong.

More information here:
en.wikipedia.org/wiki/Helminths
and here:
en.wikipedia.org/wiki/Helminthiasis


By the way, with regards to that dispute about randomized controlled trials proving or not proving the evidence for health benefits of mass deworming, if anyone is interested in that, please read the discussion of Joe, James and others here:
en.wikipedia.org/wiki/Talk:Mass_deworming

Right now, this has come to a temporary halt. Nicole Siegmund told me that we are waiting for a WHO statement that should come out in 'PLoS Neglected Tropical Diseases' soon which would proably explain the shortcomings of RCT for this kind of public health issue. Once that's out, we can cite that in the Wikipedia article on mass deworming:
en.wikipedia.org/wiki/Mass_deworming#Evidence

Regards,
Elisabeth
Dr. Elisabeth von Muench
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  • Marijn Zandee
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Re: How much evidence do we have that mass deworming of children really has much of an impact?

Dear Elisabeth,

Thank you for this link to CWW's news letter. They seem to have revamped their website, so maybe that is why it was hard to find things. The link between CWW and J&J and GS is still on the site under "partnerships and Advocacy"

Forging strong and productive partnerships and advocating for STH control are vital parts of the work of Children Without Worms (CWW). We started in 2006 as a partnership between Johnson & Johnson and The Task Force for Global Health. Since then, we have forged partnerships with others in the STH control community, including GSK, the Children’s Investment Fund Foundation, and more, through our work managing the STH Coalition and the STH Advisory Committee.


I get the impression that CWW is one of the driving forces behind the soil Transmitted Helminths (STH) coalition, which now also includes a number of WASH organizations.

The actual content of the CWW newsletter is a bit underwhelming, to say the least. I think one of the better worked out responses as to why deworming makes sense is given here:
blog.givewell.org/2015/07/24/new-dewormi...and-cochrane-review/

As far as I can make out, the people from Givewell agree with the Cochrane review that the evidence for short term health impact is weak. They also agree that there is currently no good explanation as to why people who were dewormed in these studies do better later in life, and that this lack of obvious cause-effect is problematic. However, they claim that the evidence that the people who were dewormed as children do better later in life is strong. This, combined with the relative cheapness of the programs is reason for Givewell.org to keep supporting deworming programs. ( I hope I summarized that correct :P)

Further, I also think that combining WASH interventions with deworming makes sense. As I have mentioned a few times before, I also wonder how many of these helminth infections are caused by a lack of animal manure management.

Regards

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

Dear Marijn,
It took me a little while but here is now the link to the newsletter of "Children Without Worms":
us9.campaign-archive2.com/?u=69cf8aa7d0d...4aa944b&e=2de8f51cd1

Dear Joe,
Thanks for pointing out this potential conflict of interest... On their website, they don't really state that link clearly, do they? I checked on About Us and only found:

Children Without Worms was Created as a Partnership

Partnership and collaboration have been key tenets for Children Without Worms (CWW) since our inception in 2006. Those tenets are best personified by our team of compassionate, committed staff members.


Good old Wikipedia however tells me that:

Childred Without Worms (CWW) is a global collaborative health programme among two pharmaceutical giants, Johnson & Johnson and GlaxoSmithKline, and a nonprofit organisation, the Task Force for Global Health.


Dear Arjen and Joe,

I like the idea of combining mass deworming treatment with CLTS. I think you (Arjen) are right that if people have worms before then they will still have them after the latrines are built and used because once infected the worms stay in your body, don't they? Therefore, to start with a clean bill of health after triggering and after latrine use has started, by deworming all the children (and adults, too?) once or twice, would surely make some sense?

I am actually frustrated because it seems to me that the "deworming community" and the "sanitation community" are not yet talking to each other sufficiently. We both think we are doing good things for health but perhaps the real, measurable impacts only occur when we combine forces? Toilets AND deworming and not toilets without deworming, or deworming without toilets... (and toilets AND nutrition, too...)

Arjen, would you like to fill in your forum profile a bit more so that we know more about you and your work? Thanks.

Regards,
Elisabeth
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  • Arjen
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Re: How much evidence do we have that mass deworming of children really has much of an impact?

More as a natural follow-up of ODF. It seems a bit silly that we expect better health outcomes from ODF declarations - if people had worms before, they will have them after, unless we treat it / the whole community.

Let's see what others think of it! :-)
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Re: How much evidence do we have that mass deworming of children really has much of an impact?

Ah I see what you mean. Deworming as a reward for OD. I'm not sure what to think about that!

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

Sorry, for not explaining my thoughts further. First of all, doing deworming campaigns without attaining ODF and better hygiene behaviour is in a way set to fail - and ineffective.

Therefore, I am trying to link it to the many, large scale programmes for ODF that are present world wide - but very few have a clear strategy what should happen once a community/region is Open Defecation Free. The post-ODF discussion talks about cleaner environment and solid waste - but I have yet to hear that it has been linked to a deworming campaign. The "free" was indicative as many deworming campaigns are provided for free to the people. I take your point and appreciate the remark that it obviously still has a cost.

Many programmes are looking how to "reward"/"incentivise communities to become ODF. Providing deworming may be one of the ways (though deworming itself needs good messaging!)
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