Geographic distribution and prevalence of human echinococcosis at the township level in the Tibet Autonomous Region

Abstract Background Echinococcosis is a zoonotic parasitic disease caused by larval stages of cestodes belonging to the genus Echinococcus. Echinococcosis is prevalent in 10 provinces/autonomous regions in western and northern China. A 2016 epidemiological survey of Tibet Autonomous Region (TAR) showed that the prevalence of human echinococcosis was 1.66% which is much higher than the average prevalence in China (0.24%). Therefore, understanding the prevalence and spatial distribution characteristics of human echinococcosis at the township level in TAR is critical. Methods Data from echinococcosis cases were obtained from 692 TAR townships in 2018. Cases were identified using the B-ultrasonography diagnostic method. The epidemic status of echinococcosis was classified in all townships in TAR according to the relevant standards of population prevalence indexes as defined in the national technical plan for echinococcosis control. Spatial scan statistics were used to highlight the geographical townships most at risk of echinococcosis. SPSS 21.0 was used to calculate the prevalence for cystic echinococcosis (CE) and alveolar echinococcosis (AE). For spatial clustering analyses and mapping, data were processed using ArcGIS 10.1. Spatial scan analyses were performed using SaTScan V9.5. Results In 2018, 16,009 echinococcosis cases were recorded in 74 endemic counties in TAR. The total prevalence rate was 0.53%. All the 692 townships were classified according to the order of the epidemic degree from high to low. 127 townships had prevalence rates higher than or equal to 1%. The spatial clustering scanning analysis of echinococcosis cases and exposed population showed that CE displayed one primary cluster, two secondary clusters and six minor secondary clusters. The primary cluster and other clusters were defined by Log-likelihood ratio (LLR) statistically significant values. The primary cluster covered 88 townships in 12 epidemic counties. AE displayed one primary cluster and two secondary clusters. The primary cluster covered 38 townships in 6 epidemic counties.