No abstract

Nusa Tengara Barat (NTB) province consists of two main islands, Lombok and Sumbawa, to the east of Bali Island, Indonesia. Most of the area is known to be moderately malaria endemic, but the exact malaria epidemiology has not been elucidated. At least 30 deaths per year are thought to be caused by falciparum malaria in Lombok alone, judging from the hospital data. According to the Gebrak Malaria Team in West Lombok, the annual incidence in the district of West Lombok from 1996 to 1999 was consistently over 40. In the present report, we describe the small malaria endemic foci in the West Lombok and Sumbawa districts. Falciparum malaria is predominant over vivax malaria and other types of malaria. There are 11 species of Anopheles vector, but three of these species, An. subpictus, An. maculates and An. barbirostris, are of primary importance in malaria transmission and An. sundaicus and An. aconitus are of secondary importance. Our data from Sekotong, West Lombok, and Sumbawa supported the importance of An. subpictus in coastal areas but suggested the existence of different transmission peaks according to environmental conditions. The usual transmission peak comes in the dry season but is affected by climatic and geographical conditions. Although there were many malaria endemic foci along the coast, the width and grade of the foci varied widely. The presence of malaria endemic foci inland, although likely, has not been definitively reported to date.

Malaria epidemiological surveys were carried out in two subdistricts; Meninting of Lombok island and Utan of Sumbawa island, Indonesia in 2002 through 2003. In Meninting, distribution of hypo-to meso-endemicity was observed mainly in hilly forested areas and partially in coastal areas with no distribution in the more densely populated flat areas surrounded by rice fields. In contrast, in Utan the distribution was limited to the coastal areas. In Utan, treatment follow-up studies revealed the prevalence of chloroquine resistant Plasmodium falciparum (P. f.). Although the degree of malaria endemicity in the two areas was regarded as hypo-to meso-endemic, the majority of affected individuals were under the age of ten, and the number of positive cases declined with increasing age. Interestingly, age dependence to species-specific infection was observed, younger children being more prone to P. vivax infections than to P. f.