Soil-Transmitted Helminth (STH) infections are endemic in Nan province and efforts are underway to decrease the transmission. The study aim to assess the effectiveness of participatory learning school-based intervention toward knowledge, attitude, preventive behaviors and incidence of helminthes infections among primary school students. Total 132 students (67 in experimental and 65 in control group) from grades 4-6, primary school students at Bo Kluea district were selected from three ethnic minority groups in November 2013 -...