In 1985–1987, a field trial of malaria control using deltamethrin impregnated mosquito nets was carried out with 4,450 people in the Buji district, Bao'an County, Guangdong Province, China. The vectors were exophilic Anopheles sinensis (80%) and the endophilic and anthropophilic An. anthropophagus (20%). The first impregnation of the nets was in June 1985 and the second in April 1986. About 87% of the population slept under treated nets.
The indoor vector density decreased by 93% and remained at the same level during the second year. During the second year the average monthly malaria incidence was 1.3‰ for January–June, a decrease of 74.6% as compared with pretreatment data, and 0.85‰ from July to December, a decrease of 92.7%.
In April 1986 and April 1987, the treatment was extended to the whole Buji District, which has a total population of ∼40,000. The average monthly malaria incidence (April–December 1986 and 1987) was 0.54‰ and 0.17‰, a decrease of 64.7% and 89% respectively as compared with the same period for the previous year.