The Global Debate Over Mass Deworming

The morning bell rings. One hundred children line up behind a desk.

It’s National Deworming Day.

One at a time, each child steps up and holds a hand out over the desk. A teacher drops a tablet into the child’s extended palm. It’s pink, round and familiar. Without hesitation, she plops the large tablet into her mouth and swallows it with a gulp of water. As she scurries from the table, the teacher behind the desk places a checkmark next to her name.

This checkmark indicates that one of the estimated one and a half billion humans1 affected by soil-transmitted nematodes (STN) has just been “dewormed.” From a Western perspective, this may seem like a strange concept: medicine being handed out as easily as candy. Yet, for children in many parts of the developing world, this isn’t unusual at all—it happens once, sometimes twice, a year.

In February 2015, The Indian Ministry of Health and Family Welfare launched the country’s first “National Deworming Day,” the world’s largest public health campaign aimed at treating millions of children infected with parasitic worms. More commonly known to populations of Sub-Saharan Africa, “Deworming Day” campaigns distribute single doses of deworming drugs through community or school-based platforms for the treatment of STN infections in developing countries.

The intestinal parasites Trichuris (whipworm), Ascaris (roundworm) and Necator americanus (hookworm) are neglected tropical diseases (NTDs) transmitted via contact with feces-contaminated soil. This is especially prevalent in areas with high rates of open defecation and poor sanitation. Once an individual becomes infected, these worms can reside in the gastrointestinal tract for several years, feeding on the host’s nutrients, blood, and tissues. Chronic infection with STNs can lead to anemia, poor immune function and delayed growth, especially in children.2

In 2013, an estimated 325 million tablets of benzimidazole deworming drugs were distributed to school-aged children for the treatment of STN infections.3 For the past decade, the World Health Organization (WHO) has recommended that children receive deworming drugs twice a year where over 50% of the population is infected, and once a year where 20-50% of the population is infected. The benzimidazole class of drugs is relatively safe and thus commonly distributed through school systems. The WHO recommends against screening for diagnosis prior to administering these drugs on the basis of cost-efficiency.4

A host of global health organizations have advocated strongly for deworming programs, emphasizing improvements in childhood nutritional status and school attendance. Additionally, advocates claim that school-based deworming programs efficiently target the most heavily infected parts of the population to reduce community transmission rates. Recently, however, closer scrutiny of these studies has led to substantive disagreements among public health experts, economists, and researchers, prompting the question: is mass deworming truly the most cost-effective and impactful long-term strategy for large-scale control of parasites?

Evidence Action, supported by Yale economist Dean Karlan, is the non-profit partner organization in India’s recent deworming campaign. Evidence Action previously led large-scale deworming initiatives in other parts of the world, and commonly cites studies published by Harvard economists Miguel and Kremer as evidence for the benefits of mass deworming. Miguel and Kremer claim that school-based deworming programs improve childhood school attendance and school performance by up to 24% and 6%, respectively.5 A multitude of global health organizations have cited these studies to support deworming programs due to the precise study design and conclusive results.

In 2012, however, the Cochrane Review published a comprehensive evaluation of randomized control trials gauging the direct and indirect effects of deworming programs on morbidity indicators. The authors of this review concluded that reliance on deworming programs as recommended by the WHO did not have any significant impact on childhood nutrition, anemia, school attendance and school performance. 6

From an epidemiological standpoint, researchers have posited that mass deworming every year is unlikely to reduce transmission rates across communities.7 Since infected individuals do not develop antibody-mediated protection following exposure, it is possible that contact with fecal-contaminated environments soon after treatment may leave treated individuals right where they started. This confounding issue points to greater public health issues in sanitation education and infrastructure.

Researchers have also raised concerns about drug resistance. Yale researchers Michael Cappello, MD, and Debbie Humphries, PhD, recently published an article advocating for improved monitoring systems in deworming programs, to reduce the risk of benzimidazole drug resistance.8

Despite the debate over evidence in mass drug administration, public health initiatives focusing on deworming remain popular charitable endeavors. Reputable organizations such as GiveWell, a non-profit evaluator, have supported deworming initiatives despite acknowledging the tenuous evidence base. Large pharmaceutical companies such as GlaxoSmithKline stand by their billion-dollar philanthropic efforts to donate benzimidazole drugs worldwide. However, the charity industry and global health community must critically evaluate this debate in order to support large-scale deworming initiatives in the developing world. A closer analysis of the data suggests that it might be time to rethink the WHO recommendations for mass deworming and consider other cost-effective, long-term strategies.

–

Sonya Prasad

Timothy Dwight ’15