Effectiveness evaluation of the"Three-Line Defense System"for mosquito control in African project camps

ZHANG Jianguo; SHI Buqing; ZHOU Jie; AN Hao; MA Jinhu; XIA Benli; ZHAO Randi; YU Weijie

doi:10.19821/j.1671-2781.2025.06.012

Abstract：Objective To evaluate the effectiveness of the"Three-Line Defense System"for mosquito vector control in the construction camps of African engineering projects in reducing mosquito density and malaria incidence,and to optimize this system.Methods In four camps in Chad where the system had been fully implemented,the densities of adult mosquitoes and larvae around residential areas were monitored over three consecutive malaria epidemic seasons following implementation.The annual malaria incidence among Chinese staff was also recorded.The correlation between changes in mosquito vector density and malaria incidence was analyzed,and the"Three-Line Defense System"was refined accordingly,incorporating supporting management measures.Results The implementation of the"Three-Line Defense System"and supporting management measures significantly reduced the densities of adult mosquitoes and larvae in the camps(both P≤0.01),with reduction rates of 88.79%and 96.49%,respectively.This low-density state remained stable throughout the three-year monitoring period(P≥0.05).The malaria incidence among staff showed a significant positive correlation with adult mosquito density(r=0.838,P≤0.01)and larvae density(r=0.851,P≤0.01).After system implementation,malaria incidence decreased by80.38%.Conclusion The integrated"Three-Line Defense System"for mosquito vector control,combined with supporting management measures,the density of adult mosquitoes and larvae in African engineering project camps can be effectively,significantly and continuously reduced,thereby significantly lowering the malaria incidence among Chinese staff.This system demonstrates stable effectiveness and holds significant public health value,making it suitable for broader application in similar overseas engineering projects.