In 1962, Norman Stoll, the distinguished Rockefeller Institute scientist who helped to establish human parasitology research in North America, described the unique health impact of hookworm as follows [1]:

As it was when I first saw it, so it is now, one of the most evil of infections. Not with dramatic pathology as are filariasis, or schistosomiasis, but with damage silent and insidious. Now that malaria is being pushed back hookworm remains the great infection of mankind. In my view it outranks all other worm infections of man combined…in its production, frequently unrealized, of human misery, debility, and inefficiency in the tropics.

Human hookworm infection is caused by blood-feeding nematode parasites of the genus Ancylostoma and the species Necator americanus. Worldwide, N. americanus is the predominant etiology of human hookworm infection, whereas A. duodenale occurs in more scattered focal environments [3]. These two hookworms, together with the roundworm, Ascaris lumbricoides, and the whipworm, Trichuris trichiura, are often referred to collectively as soil-transmitted helminths (STHs).

Hookworm infection is acquired by invasion of the infective larval stages through the skin (A. duodenale larvae are also orally infective). Following host entry, the larvae undergo a journey through the vasculature, then the lungs and other tissues, before they enter the gastrointestinal tract and molt twice to become one-centimeter-long adult male and female worms [3]. The worms mate and the female hookworms produce up to 30,000 eggs per day, which exit the host's body in the feces (Figure 3).

Because of its high transmission potential, hookworm has proven to be extremely difficult to eliminate or eradicate in areas of poverty and poor sanitation [19]. Indeed, in the absence of comprehensive economic development, the impact of sanitation, footwear, and health education has been minimal [19]. Control efforts have therefore shifted to reducing morbidity through mass treatment (also known as “deworming”) of affected populations with anthelminthic drugs [19].

Deworming satisfies a number of United Nations Millennium Development Goals including those related to poverty reduction, child health, and education. However, there are also several reasons to believe that the school-based deworming programs could have less of an impact on the control of morbidity from hookworm than from other STH and schistosome infections [3]. As noted above, heavy-intensity hookworm infections are common among both adults and children, so school-based programs would not be expected to have an impact on hookworm transmission in the community [24]. School-based programs are also not likely to affect either preschool children or pregnant women, despite evidence for the health benefits from BZAs in both populations [16,25]. Finally, a single dose of mebendazole (one of the two major BZAs) has variable efficacy against hookworm [26], and following treatment, hookworm reinfection to pre-treatment levels can occur within 4–12 months [27]. This, and the observation that the efficacy of mebendazole against hookworm can diminish with frequent and repeated use, has prompted concerns about the possible emergence of BZA resistance [28].