Mass deworming

Mass deworming, is one of the preventive chemotherapy tools, used to treat large numbers of people, particularly children, for worm infections notably soil-transmitted helminthiasis, and schistosomiasis in areas with a high prevalence of these conditions. It involves treating everyone – often all children who attend schools, using existing infrastructure to save money – rather than testing first and then only treating selectively. Serious side effects have not been reported when administering the medication to those without worms, and testing for the infection is many times more expensive than treating it. Therefore, for the same amount of money, mass deworming can treat more people more cost-effectively than selective deworming. Mass deworming is one example of mass drug administration.
Mass deworming of children can be carried out by administering mebendazole and albendazole which are two types of anthelmintic drug. The cost of providing one tablet every six to twelve months per child is relatively low.
Soil-transmitted helminthiasis is the most prevalent neglected tropical disease. Over 870 million children are at risk of parasitic worm infection. Worm infections interfere with nutrient uptake, can lead to anemia, malnourishment and impaired mental and physical development, and pose a serious threat to children's health, education, and productivity. Infected children are often too sick or tired to concentrate at school, or to attend at all. In 2001, the World Health Assembly set a target for the World Health Organization to treat 75% of school-aged children by 2010.
Some non-governmental organizations support mass deworming, such as the Deworm the World Initiative, the END Fund, the Schistosomiasis Control Initiative, and Sightsavers. Because of the low cost of deworming children, large-scale implementation may provide wider benefits to society.

Background

Intestinal parasitic worms affect approximately 1.5 billion people, according to WHO estimates, with 218 million needing preventive treatment for schistosoma-type worms in 2015.
The World Health Organization recommends mass deworming of children who live in endemic areas, in order to reduce morbidity by reducing the overall worm burden. The WHO advises that worm infections adversely affect nutritional status, impair cognitive processes, and can cause conditions such as intestinal obstruction or lesions in the urinary tract and liver. Periodic drug treatment is expected to bring about health benefits such as reduced micronutrient loss, reduced environmental contamination, improved nutritional status and cognitive function, and better school performance in certain circumstances.
In 2001, the World Health Assembly set a target for the WHO to treat 75 percent of school-aged children by 2010. In 2014, over 396 million preschool and school-aged children were treated, corresponding to 47 percent of children at risk.

Methods

Pills

Deworming programmes for children usually administer an anthelmintic drug such as albendazole or mebendazole. The treatment is given as a single dose in a pill formulation. Other drugs used, though not approved by the WHO, include pyrantel pamoate, piperazine, piperazine citrate, tetrachloroethylene, and levamisole. In mass deworming programs, all children are given the medication, whether they are infected or not. In endemic areas, the deworming needs to be repeated regularly. The frequency of the treatment depends on the prevalence and severity of infection which is determined by periodic surveys but is usually required annually.

Accompanying measures

To increase the benefits of mass deworming and to lower the rate of reinfection, accompanying measures of mass deworming programmes should include water, sanitation and hygiene interventions. A good example for such a combined intervention is the Essential Health Care Program implemented by the Department of Education in the Philippines: This national programme combines twice annual deworming of school children with group handwashing with soap at set times of the day at the school premises. This so-called "Fit for School" approach has also been implemented in Indonesia in 2014.

Health aspects

Evidence

In 2015, a review in a World Bank journal concluded that evidence supports a benefit with respect to school attendance and long term income.
A Cochrane review updated in 2019 found that high-quality medical evidence on mass deworming of children did not support beneficial effect on school performance, body weight, cognition, and rates of anemia. However, it excluded a number of studies which showed positive long-term results as they did not meet the inclusion criteria of a pure control. Supporters of mass deworming argue that these studies make a case for long-term benefits.
A review in 2016 examining the effects of deworming on child weight included studies omitted from Cochrane. It also extracted additional data from included studies. This 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.
In 2017, a systematic review and meta-analysis re-examined available studies and concluded that mass deworming for soil-transmitted helminths had little effect. However, for schistosomiasis, mass deworming might have been effective for weight but probably was ineffective for height, cognition, and school attendance.
A 2019 meta-analysis from the Campbell Collaboration found that mass deworming of pregnant women reduced maternal anemia by 23%, but there was no evidence of other effects.
Reinfection and resistance

Reinfection with worms may begin shortly after the pill has killed the intestinal worm population. Regular re-treatment together with an increased focus on other aspects of water, sanitation and hygiene reduces the rates of infection in areas where parasitic worms are endemic.
Resistance of worms to anthelmintic drugs over time is a possibility.

Costs

Mass deworming has been determined to be cheap when calculated on a 'per child/per year' or $/DALY basis. Screening test to detect if a child is actually infected would be up to 12 times more expensive.
The cost of treating a child for infection of soil transmitted helminths and schistosomes costs different amounts in different countries when administered as part of mass school-based deworming, but Evidence Action states that their recent programmes cost $0.56 or less per child per dose. This programme is recommended by Giving What We Can and the Copenhagen Consensus Centre as one of the most efficient and cost-effective solutions. Modelling studies also suggest that deworming programmes are highly cost effective.

National deworming programmes

National deworming programmes target children of school age, which the WHO defines as being between 5 and 14 years of age. By 2015, the total global number estimated to be in deworming programmes was 495 million and national deworming programs had been started in a number of countries. The world's largest deworming programme was started in 2015 in India, with an aim to target 240 million children at risk for parasitic worms.
National deworming programmes listed by country in alphabetical order:

Burundi: around 2 million children received two doses of medication in 2014.
Cameroon: began a deworming programme in 2006, it expanded to target 4 million children.
Côte d'Ivoire: more than 1.4 million children treated in 2014
Central African Republic: began a deworming programme in 2015 aiming to target 250,000 children.
Democratic Republic of Congo: began a deworming campaign in 2009 aiming to target 12.5 million children.
Ethiopia: announced it would begin a national deworming programme in 2015. following an estimated 6.8 million children treated in 2014.
Gambia: began a deworming programme in 2010, by 2013 it was targeting 1.6 million children.
Kenya: began a deworming programme in 2009 of all children in 45 districts of high density STH infections. By 2014, the programme had expanded to target 6 million children.
India: announced a deworming programme in 2015 which aimed to treat 240 million children.
Liberia: more than 600,000 children treated in 2014, but delayed due to ebola
Madagascar: began a deworming programme in 2012 aiming to target all of the children in the country, more than 5 million in total.
Malawi: around 2 million children targeted in a deworming programme in 2011.
Mozambique: began a deworming programme in 2007 when nearly 500,000 children were treated, by 2014 around 5 million were targeted.
Niger: began a deworming programme in 2004, in 2014 more than 1.3 million children.
Senegal: more than 500,000 children treated in 2013.
Sierra Leone: 1.1 million school children received two doses of medication in 2011
Tanzania: more than 960,000 children treated in 2014.
Uganda: more than 500,000 received a biannual treatment in 2014.
Yemen: more than 2.5 million children treated in 2014, but programme on hold in 2015 due to political unrest.
Zambia: more than 90,000 children treated in 2014.
Zanzibar: almost 1.7 million children treated in 2014.
Acceptance

Deworming programmes are widely accepted, although there have been some reports of parents refusing to allow their children to receive medication due to fears of illness, such as those reported in the media in the Philippines.
One survey in the Philippines reported that some parents will not allow their children to receive deworming tablets, while the majority would. Another in rural China found that skepticism and local rumors about the deworming programme could affect the uptake of medication.