Species and population density of malaria vector Anopheles in Sichuan Province from 2011 to 2021

Abstract

To investigate the distribution of malaria vector Anopheles in Sichuan Province from 2011 to 2021, so as to provide the scientific evidence for improving the surveillance of malaria vector Anopheles and preventing re-establishment of imported malaria in Sichuan Province. The density and species of Anopheles mosquitoes were investigated using human-bait trapping and light trapping techniques in malaria vector surveillance sites of Sichuan Province from 2011 to 2021. The number, population and density of captured Anopheles mosquitoes were collected and descriptively analyzed, and the geographical distribution map of malaria vectors was plotted using the software ArcGIS 10.7 in Sichuan Province. A total of 152 243 Anopheles mosquitoes were captured in malaria vector surveillance sites of Sichuan Province from 2011 to 2021, including 150 987 An. sinensis (99.18%) and 1 256 An. anthropophagus (0.82%), and no other Anopheles species were captured. The annual densities of An. sinensis and An. anthropophagus were 0.64 to 1.27 mosquitoes/(person-hour) and 0 to 0.07 mosquitoes/(person-hour) by the human-bait trapping technique, and 6.46 to 26.50 mosquitoes/(light-night) and 0 to 0.82 mosquitoes/(light-night) by the light trapping technique in malaria vector surveillance sites of Sichuan Province from 2011 to 2021. A relatively higher density of An. anthropophagus was seen in Renshou County, Jianyang City, Weiyuan County and Mabian Yi Autonomous County [> 0.40 mosquitoes/(person-hour)] by the human-bait trapping technique, and in Cuiping District and Gaoxian County in Yibin City [> 1.00 mosquito/(light-night)] by the light trapping technique in Sichuan Province from 2011 to 2018, with no An. anthropophagus captured from 2019 to 2021, and a relatively higher density of An. sinensis was detected in Emeishan City, Lushan County, Luojiang District, Tongchuan District and Zhaohua District [> 4.00 mosquitoes/(person-hour)] by the human-bait trapping technique, and in Huili County, Yuexi County, Dechang County, Langzhong City, Pingchang County and Xuanhan County [> 40.00 mosquitoes/(light-night)] by the light trapping technique in Sichuan Province from 2011 to 2021. Malaria vectors were still widespread in Sichuan Province from 2011 to 2021, and An. sinensis was the dominant species of malaria vectors. There is still a risk of local re-establishment of imported malaria in Sichuan Province, and it is needed to continue to improve the surveillance of imported malaria cases and malaria vectors.