Soil transmitted helminth infections (STH) are caused by species, including Ascaris lumbricoides, hookworm (Ancylostoma duodenale and Necator americanus) and Trichuris trichiura.  STH infections may be asymptomatic, heavy infections are associated with considerable morbidity, including abdominal pain, diarrhea and anemia, as well as impaired cognitive and physical development in children. STH infections focus on morbidity control through the use of mass drug administration (MDA) of anthelmintic drugs targeting preschool- and school-aged children as well as other at-risk groups.