[Longitudinal surveillance of schistosomiasis in hilly regions of Sichuan Province from 2015 to 2019].

Objective: To investigate the changes in the endemic situation of schistosomiasis in national surveillance sites of Sichuan Province, so as to provide the scientific evidence for formulating the schistosomiasis elimination strategy.
Methods: From 2015 to 2019, 63 national schistosomiasis surveillance sites were assigned in Sichuan Province, in which Schistosoma japonicum infections were monitored in humans, livestock, wild feces and snails. The monitoring data were descriptively analyzed.
Results: A total of 94 119 person-time local residents were serologically screened for S. japonicum infections in 63 national surveillance sites of Sichuan Province from 2015 to 2019, with sero-prevalence rates ranging from 1.28% to 3.11%, and the sero-positives were predominantly detected in local residents at ages of over 50 years and in farmers. A total of 94 119 person-time mobile populations were serologically screened for S. japonicum infections in the national surveillance sites during the 5-year period, with sero-prevalence of 1.10% to 1.59%. There were no egg-positives identified in either local residents or mobile populations. Among the 6 126 herd-time livestock detected, no egg-positives were identified, and no S. japonicum infection was detected in the 205 wild feces. Snail survey was performed covering an area of 8 484.08 hm ² , and 724.80 hm ² snail habitats were identified, including 2.43 hm ² emerging snail habitats and 63.00 hm ² re-emerging snail habitats. The mean occurrence of frames with snails was 6.87% to 19.63%, and the mean density of living snails was 0.18 to 0.62 snails/0.1 m ² in the national surveillance sites of Sichuan Province from 2015 to 2019; however, no S. japonicum infection was detected in snails.
Conclusions: The endemic situation of schistosomiasis has reduced to the lowest level in Sichuan Province; however, there is a rise in snail habitats, and there is still a risk of schistosomiasis resurgence. Further improvements of the surveillance system for schistosomiasis are required to achieve the goal of schistosomiasis elimination in Sichuan Province as soon as possible.