Mass deworming, is one of the preventive chemotherapy tools,[1][2] 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.

[8] 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.

[14] 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.

[25] Regular re-treatment together with an increased focus on other aspects of water, sanitation and hygiene (WASH) reduces the rates of infection in areas where parasitic worms are endemic.

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.

[47] Biotechnology companies in the developing world have targeted neglected tropical diseases – which many helminth infections are classified as – and mass drug administration due to a need to improve global health.

[50] The national deworming programme was established as a partnership between the Pan American Health Organization – which serves as the Regional Office of the WHO, the Global Network for Neglected Tropical Diseases, the Inter-American Development Bank, Nicaraguan Government ministries, International NGOs and the main donor Children Without Worms.

[51] In 2007, Burundi undertook a parasitological survey across its population which demonstrated that intestinal schistosomiasis was highly focalised in areas close to water and soil-transmitted helminthiases, including hook worm, was more widely distributed amongst its people.

[52] The Schistosomiasis Control Initiative had developed an approach which would cost 50 US cents per person per year, and was piloted in Burundi and Rwanda in 2007 with a $9 million investment from the Legatum Foundation, along with support from various other government donors, philanthropists and pharmaceutical companies, over a four-year period.

[54] However, in 2013 the Director of the National Institute of Health in the Philippines questioned the effectiveness of the programme because it only covered only 20% of affected children with an infection rate of 44%.

[58] Other national press reports in July 2015 stated that a small number of children had been admitted to hospital due to an "adverse effect" of the deworming medication.

[59][61] This campaign was enthusiastically received by educators throughout the region; as one Virginian school observed: "children who were listless and dull are now active and alert; children who could not study a year ago are not only studying now, but are finding joy in learning... for the first time in their lives their cheeks show the glow of health.

"[61] From Louisiana, a grateful school board added: "As a result of your treatment ... their lessons are not so hard for them, they pay better attention in class and they have more energy ...

"[61] Military personnel returning from the Second World War were found to be bringing intestinal worms back to the United States, so in 1947 the American Society of Parasitologists called for increased attention on deworming.