*2.3. Disease Diagnosis*

During the study period, after the transmission season (October–November), residents aged 5 to 65 years (743 in Sanlian, 1479 in Guifan in 1981) were tested by Kato-Katz (KK) fecal test and/or indirect hemagglutination assay (IHA) [9]. After 1981, the number of examined people was about 600 to 1200 in Sanlian and Guifan, respectively. From 1981 to 1994, all subjects in the two villages were tested by the two Kato-Katz thick smears test. During the period of 1995–2004, subjects were screened by indirect hemagglutination assay method. From 2005 to 2014, all subjects were tested by three Kato-Katz thick smears test. All the subjects were screened by indirect hemagglutination assay and the seropositive were confirmed by Kato-Katz three smears test from 2015 to 2017.
