Efficacy of permethrin-impregnated bed nets on malaria control in a hyperendemic area in Irian Jaya, Indonesia: differentiation between two age groups.

A malaria intervention trial was conducted for two years to evaluate the efficacy of permethrin-impregnated bed nets in reducing malaria infection and splenomegaly in two different age groups, ie below and over age of ten, in a hyperendemic area in Irian Jaya, Indonesia. Permethrin-impregnated or placebo-treated bed nets were provided to a treated and a control village, respectively. Immediately after periods with moderate rainfall in the first year, treated bed nets decreased P. falciparum and P. vivax density in the blood of children <10 years (group 1) but did not reduce the percentage of infection with either species. Children >10 and adults (group 2) showed significant reduction only in P. falciparum infection rates and density, whereas P. vivax was not influenced. After an excessive rainfall season in the second year, the risk for P. falciparum infections in both age groups using treated nets was less than half of that in the control village. P. vivax infection rates were significantly lower in the treated village at the beginning of and after these heavy rainfalls. In the treated village, spleen enlargement was markedly reduced in the younger age group during the second year.

Mosquitoes of Bali Island, Indonesia: common species in the village environment.

Routine sampling of mosquito populations in rural villages was carried out during 13 months at 4 locations in southern Bali Island, Indonesia. Sampling was by light trapping and early night resting collections around animal stables. Specimens collected were preserved for assay of arthropod-borne viruses; 104,608 specimens representing 20 species were prepared in 2681 pools for viral assay. Anopheles barbirostris and An. subpictus have been shown to be important vectors of Brugia malayi and B. timori and of malaria and Wuchereria bancrofti in other parts of Indonesia but have not been incriminated in transmission of disease agents in Bali. Anopheles vagus may be involved in filarial transmission in other regions but is not regarded as important in Bali. Culex fuscocephala, Cx. gelidus and Cx. tritaeniorhynchus have been incriminated in the transmission of Japanese encephalitis virus in Indonesia and Cx. vishnui has been similarly implicated in other countries. The populations of these mosquitoes are compared and plotted against rainfall. The potential of the more common species as vector of some human pathogens is discussed.