5. These observations are summarized in Hotez, 2002.
6. These observations are reported in Fenghua et al., 1998.
7. From de Silva et al., 2003.
8. Factors underlying the relationship between STH infection and poverty are described in Raso et al., 2005; Holland et al., 1988; and Hotez, 2008.
9. The exact mechanisms by which STHs impair growth and development are still poorly understood. An excellent review of the literature is found in Crompton and Nesheim, 2002.
11. The link between STHs and impaired cognition and memory has been studied extensively by D. A. P. Bundy and his colleagues. Two important papers include Nokes et al., 1992; and Sakti et al., 1999. However, the mechanisms by which worms impair cognition and memory are not well understood.
12. Bleakley, 2007.
13. The GBD 2010 study is found in Murray et al., 2012, and Vos et al., 2012.
14. Original maps of the distribution of all three STH infections can be found in de Silva et al., 2003.
15. An excellent historical account of hookworm in the United States is found in Ettling, 1981. A more global perspective can be found in Farley, 2004. Whether or not hookworm or other STH infections are still endemic in the United States is not known, given that no major studies have been conducted in more than 30 years; see Starr and Montgomery, 2011.
16. Humphreys, 2001, p. 110–111.
17. A summary of the impact of sanitation and health education on STH infections is found in Asaolu and Ofoezie, 2003; and Ziegelbauer et al., 2012. A study showing the absence of a relationship between wearing shoes and avoiding hookworm infection is found in Bethony et al., 2002.
18. Descriptions of the hookworm life cycle and the clinical manifestations of hookworm are found in Hotez et al., 2005; and Hotez et al., 2004.
19. Studies showing a high hookworm prevalence and intensity in coastal regions (regions with sandy soils) are in Mabaso et al., 2003; and Mabaso et al., 2004.
20. The biochemical mechanism by which hookworms digest blood is described in Williamson et al., 2004.
21. Some of these calculations can be found in Stoltzfus et al., 1997a; and Stoltzfus et al., 1997b. They are summarized in Crompton, 2000; and Crompton and Nesheim, 2002. The link between moderate and heavy hookworm infections and intestinal blood loss leading to iron deficiency anemia was recently confirmed in a systematic review; see Smith and Brooker, 2010.
22. The global importance of hookworm in pregnancy is highlighted in Bundy et al., 1995; and Christian et al., 2004. A recent systematic review confirmed the link between hookworm and anemia in pregnancy and provided the estimate of the number of hookworm-infected pregnant women in sub-Saharan Africa; see Brooker et al., 2008.
23. Data are summarized in Hotez et al., 2006b. New information about years lost from disability can be found in Vos et al., 2012.
24. Information on the control of STH infections through deworming is summarized in Albonico et al., 2006; Brooker et al., 2004; and Crompton and Nesheim, 2002. The educational and economic benefits of deworming are discussed in Miguel and Kremer, 2004; Baird et al., 2012; and Bleakley, 2007. Some of these studies operate under the auspices of the innovative Abdul Latif Jameel Poverty Action Lab, based at Massachusetts Institute of Technology (www.povertyactionlab.org), and the Partnership for Child Development in London (www.child-development.org). Some investigators consider the improvements in child cognition that result from deworming to be marginal or controversial; see Taylor-Robinson et al., 2012. This paper stimulated a lively debate (in which I participated) published as a blog in the PLOS Medicine Speaking of Medicine community blog (PLOS Medicine, 2012).
25. Hotez et al., 2006a; World Bank, 2003.
26. Savioli et al., 1992.
27. Estimates of the scope of global deworming and other NTD interventions are in World Health Organization, 2012.
28. The information about resistance is summarized in Brooker et al., 2004. The systematic review of the efficacy of drugs for STH infections is found in