National surveillance of schistosomiasis morbidity in China, 2015-2019

Abstract

To understand the morbidity due to Schistosoma japonicum in national schistosomiasis surveillance sites of China from 2015 to 2019, so as to provide insights into schistosomiasis control and elimination and provide the scientific evidence for formulating the new scheme for schistosomiasis surveillance in China. According to the requirements of National Scheme for Schistosomiasis Surveillance in China (2014 Edition), national schistosomiasis surveillance sites were assigned in all schistosomiasis-endemic counties (cities, districts) and the potential endemic counties (cities, districts) in the Three Gorges Reservoir areas, and S. japonicum infections were monitored in local residents, mobile populations and livestock according to different epidemic types. The sero-prevalence of S. japonicum infections, adjusted prevalence of human S. japonicum infections, characteristics of egg-positive individuals and prevalence of S. japonicum infections livestock were analyzed. S. japonicum infections were monitored in 453 schistosomiasis-endemic counties (cities, districts) from 13 provinces (municipalities, autonomous regions) and 4 potential endemic counties (cities, districts) from the Three Gorges Reservoir areas in China from 2015 to 2019. During the 5-year period from 2015 to 2019, the sero-prevalence of S. japonicum infections reduced from 3.35% to 1.63% among local residents and from 1.15% to 0.75% among mobile populations, while the adjusted prevalence of infections reduced from 0.05% to 0 among local residents and from 0.20% to 0.001 03% among mobile populations. There were significant differences in the sero-prevalence of S. japonicum infections among local residents and mobile populations in terms of province, occupation and age (all P values < 0.05). A total of 132 egg-positives were identified during the 5-year period, including 97 local residents (inter-quartile range for ages, 47 to 61 years), and 35 mobile populations (inter-quartile range for ages, 26 to 48 years), and there was a significant difference in the age distribution between local residents and mobile populations (P < 0.05). There were totally 6 bovines (5 in 2015 and 1 in 2016) identified with S. japonicum infections in national schistosomiasis surveillance sites of China, with no S. japonicum infections detected in bovines from 2017 to 2019. The prevalence of schistosomiasis is very low in China. Further surveillance including more mobile surveillance sites seems justified to identify the risk of schistosomiasis as soon as possible and interrupt the transmission route, so as to facilitate the elimination of schistosomiasis in China.