Endemic coastal malaria in the Thousand Islands District, near Jakarta, Indonesia.

OBJECTIVES To conduct malaria surveillance near Jakarta where only imported malaria has been described over the past two decades and to characterize endemicity and risk to heavily populated peri-urban locations. METHODS Standard cross-sectional malariometric surveys and mosquito collections at the Thousand Islands District and developing peri-urban areas of Jakarta. RESULTS During October 2000 outbreak investigations in the Tidung Island group, the slide positive rate was 47% (38%Plasmodium falciparum, 7%P. vivax, and 2% mixed infections) among 733 persons screened. Very few parasitemic inhabitants were symptomatic (< 1%), and native residents were more commonly infected than immigrants (odds ratio 1.72), consistent with endemic autochthonous transmission. Adult and larval mosquito collections detected Anopheles sundaicus. In June 2001, prevalence of parasitemia at Pari Island, where sampling was adequate for comparison, remained high, 32%vs. 43% previously. Among 1377 individuals screened at nearby Tangerang District, a heavily populated mainland suburb dominated by fishponds through which many islanders travel to Jakarta, only 19 malaria infections were identified, all imported from Pari Island. Entomological surveillance in Tangerang identified An. subpictus, An. vagus, and An. barbirostris, all considered minor malaria vectors on Java. CONCLUSIONS Malaria is endemic in the Tidung Island group. Imported malaria occurs in the heavily populated Tangerang District where coastal development is increasing and vector breeding sites and demographic patterns lend increasingly to malaria importation and risk of emergent malaria. Careful attention to the impact of coastal development activities on vector populations and efforts to prevent introduction of An. sundaicus are warranted.