Field evaluation of bednets impregnated with deltamethrin for malaria control

Trials were undertaken in a hypoendemic area of malaria in an area bordering Vietnam, in Napo County of Guangxi Zhuang Autonomous Region, China. The aim was to compare the relative cost effectiveness of DDT residual spraying and of bednets impregnated with deltamethrin in the malaria control program. The trials were divided into three subgroups: (1) two farming areas and one coal mining area with a total population > 20,000, where the trial consisted of mass bednets impregnated with deltamethrin 15 mg/m2 net surface once a year, (2) one farming area with a population of approximately 3,600 where DDT residual spraying at 2g/m2 was carried out twice a year in May and August; (3) one farming area and one coal mining village with a population of > 4,000 were used as a control. The malaria vector population consisted mainly of Anopheles minimus and An. anthropophagus with a small contribution from An. sinensis. After bednets were impregnated with deltamethrin the mosquitos resting on the surface of the bednets decreased significantly, although there was less effect on the total vector population. The results showed that malaria incidence decreased significantly both in areas where impregnated bednets were used and in areas where residual spraying was undertaken. The positive IFAT rates of residents who slept under impregnated bednets decreased significantly in farming areas, especially in that area where bednet impregnation as a vector control measure had been undertaken for two years, but there was no change in the IFAT rate in DDT sprayed or control areas.(ABSTRACT TRUNCATED AT 250 WORDS)