Figure 2.

Soil-transmitted helminths trend during 1987–2017 in the Bolivian Chaco. A Hymenolepis nana trend was also shown as an example of the feco–oral-transmitted parasite. The study population constituted a general population in 1987 (n = 381) [5] and 2013 (n = 223) [9], pre-school- and school-aged children (SAC) in 1990 (n = 179) [10] and 2011 (n = 268) [7], and only SAC in 2016 (n = 426) and 2017 (n = 520) [10]. In 1987 and 2011, the surveyed areas included both rural and urban areas, while other surveys were limited to rural areas.