About two billion people are affected by either schistosomiasis or helminth infections transmitted through soil (such as roundworms, whipworms, and hookworms). And about 300 million people have severe and permanent ill health as a result, especially poor and marginalised groups. Children aged 2 to 5 years are most at risk of severe morbidity. Treatment is cheap and safe and need be given only two or three times a year. The benefits of such treatment, even for preschool children, are becoming clearer. A randomised controlled trial by Alderman and colleagues reported in this week's BMJ finds that adding deworming drugs to a …