Deworming the world.

Worms or helminths have historically infected more than half the world's population, but were largely neglected by medical science and public health interventions because they were considered non-fatal and of minimal clinical significance. During the 1980s, several oral drugs that were originally developed for veterinary use were discovered to cure, in a single dose, most human helminth infections. This allowed the first systematic population-based studies of the morbid sequelae of chronic worm infection and their potential reversibility after treatment. Based on these studies, we now know that almost all infected children and many adults, particularly pregnant and lactating women, suffer adverse effects from worms, including growth stunting, anemia, decreased cognitive development, and poor birth outcomes as well as poor school and work performance. Worm-infected people also respond less well to vaccinations and are more susceptible to several co-conditions such as HIV and cirrhosis. Based on these findings, several vertically organized national control programs were initiated in developing countries against schistosomiasis and the soil-transmitted helminths (hookworm, ascariasis, and whipworm). In 2005, the impact of helminth infections was redefined in terms of disability-adjusted life years (DALYs). All worm infections amenable to population-based mass chemotherapy are thought today to cause 30 million DALYs worldwide or very close to the worldwide impact of tuberculosis (TB) or malaria. In addition, almost all worm-induced DALYs are potentially reversible or preventable with periodic treatment. In 2001, the World Health Assembly advocated for mass deworming to reach 75% of the at-risk school-aged children of the world, but by 2011 only 13% had been reached. The recent large donations of anti-helminth drugs by major pharmaceutical companies linked to the inclusion of the "neglected tropical diseases" into current priorities for AIDS/TB and malaria now represent the best hope for closing this gap.