Figure 2.9 Severe hookworm disease. The child is both pale and edematous, thus reflecting severe loss of both iron and protein. (Image from Public Health Image Library, CDC [http://phil.cdc.gov].)
Hookworm is also an important health threat during pregnancy, and an estimated 44 million pregnant women worldwide suffer from hookworm infection. Additional estimates indicate that almost 7 million pregnant women in sub-Saharan Africa (almost one-third of all pregnant women) are infected with hookworm.22 Pregnant women typically have low iron reserves and are often iron deficient to begin with because of the iron demands of a growing fetus. There is a strong link between the added iron losses and anemia that result from hookworm and adverse maternal-fetal outcomes such as neonatal prematurity, low birth weight, and increased maternal mortality.21,22 Among agricultural laborers, chronic hookworm iron deficiency results in impaired worker productivity and productive capacity. In the early part of the 20th century, the Brazilian writer Monteiro Lobato created the now famous character of Jeca Tatu, a laborer who is always lazy and lacking in energy until he is cured of his hookworm infection and then goes on to champion social causes (Fig. 2.10). The chronic disabilities associated with impaired child development, poor pregnancy outcome, and reduced worker productivity account for the observation that hookworm costs more healthy life years lost through disability annually than any other parasitic worm infection.23
Given that shoes do not protect against hookworm infection, what might be our options for controlling or preventing hookworm in developing countries? The sanitary disposal of human feces by increased use of latrines could under some circumstances dramatically reduce the prevalence of hookworm and other STH infections. However, the best evidence to date is that unless it is accompanied by substantial poverty reduction measures and urbanization, the isolated use of latrines has minimal impact on the transmission of hookworm or other STH infections.17 Currently, the most effective approach to the control of STH infections is through deworming of large populations through mass drug administration of a specific anthelmintic with the ability to expel all three major parasite species. This approach is the first example that we will describe in which mass drug administration (frequently abbreviated as MDA) is used for the large-scale control or elimination of an NTD.
Figure 2.10 (Left) A Brazilian worker with amarelao, chronic hookworm infection (from Klintowitz, 1989; TAM Airlines Magazine). (Right) Jeca Tatu.
For the STHs, anthelmintic drugs belonging to the benzimidazole class (sometimes referred to as benzimidazole anthelmintics or BZAs) are primarily used in a single dose for purposes of mass deworming. The two major available BZAs are albendazole and mebendazole. Both drugs are available as low-cost generic products, and in some cases BZA donations are being organized through two programs housed at the Task Force for Global Health in Atlanta, including a Johnson & Johnson program for mebendazole donations and a GlaxoSmithKline program for albendazole. Because school-age children are particularly at risk for heavy STH infections with large numbers of worms, this group is the major one targeted for global deworming efforts. Frequent and periodic deworming of school-age children with BZAs has been shown to result in a number of pediatric health and nutritional benefits, including improvements in appetite, physical fitness, and physical growth, as well as improved iron status and reductions in anemia.11,24 Deworming also produces neuropsychiatric progress, including positive intellectual and cognitive effects, such as improvements to short-term and long-term memory, problem solving, language, and cognition.11,24 Michael Kremer and Ted Miguel, economists at Harvard University and the University of California, Berkeley, respectively, have recently confirmed the benefits of deworming in promoting educational advancement, while additional economic analyses conducted by Kremer and Miguel together with Sarah Baird and Joan Hicks, as well as Hoyt Bleakley of University of Chicago, suggest that these effects may also translate into economic benefits for the community.10,11,24
Every May, the world’s ministers of health meet at the annual World Health Assembly, held at WHO headquarters in Geneva, Switzerland. At the 54th World Health Assembly in 2001, a resolution was adopted (Resolution 54.19) that urged member nations to attain a minimum target of regular deworming of at least 75% and up to 100% of all at-risk school-age children (www.who.int/wormcontrol). Since then, there has been heightened advocacy by the WHO and other international agencies for the administration of BZAs, typically a single dose of either albendazole or mebendazole, on a large scale. Increasingly, annual deworming is being practiced in schools because of the cost-effectiveness and efficiencies of having teachers rather than health care practitioners administer anthelmintic drugs.25 This approach includes using schoolteachers who are specially trained to deliver the deworming tablets alongside health education messaging.24 In many African and Asian countries, deworming is linked with school feeding programs sponsored by the World Food Programme (www.wfp.org) and through the FRESH Partnership (Focusing Resources on Effective School Health), an interagency initiative of the World Bank, UNICEF, UNESCO, and WHO (www.freshschools.org), as well as nongovernmental organizations such as the Partnership for Child Development (www.child-development.org) and Deworm the World (www.dewormtheworld.org).24 Such interventions can be achieved for extremely low costs. For example, in Ghana and Tanzania, hundreds of thousands of children have been treated for as little as US$0.03 and $0.04 per capita.24,25 In addition to the fact that the BZAs are often donated for free, another reason that the costs of school-based deworming are so low is that the excellent safety profile of a single dose of a BZA allows children to be treated regardless of whether they are infected with STHs. Instead, once it is established that the overall community prevalence of STH infections exceeds 50%, it no longer is necessary to conduct fecal examinations on each child. Authorities can then blanket the school with a single dose of either mebendazole or albendazole. This practice eliminates the high cost of bringing trained microscopists and laboratory equipment to the school. I believe that the advocacy efforts of two individuals, namely, Lorenzo Savioli at WHO and Don Bundy, now at the World Bank, were especially instrumental in promoting global deworming and advancing the agenda leading to Resolution 54.19.26