[The state of vector-borne diseases in Indonesia]

From epidemiological point of view, Indonesia is an extremely interesting area owing its insular structure and ecological, anthropological, cultural and economical diversity. As everywhere, vector-borne diseases are the result of complex and variable epidemiological systems, subject both to biogeographical rules and human activity. Two main arboviroses are present in Indonesia: dengue and Japanese encephalitis. Dengue appears as an endemoepidemic disease and is mostly circumscribed to urban areas. Haemorrhagic cases were first observed in 1968; since then, the incidence has been constantly increasing and the disease is now one of the principal causes of child lethality. Japanese encephalitis is a rural endemic disease transmitted by rice-field mosquitoes; its incidence remains relatively low since pigs, which are usual link-hosts for the virus, are uncommon in this mainly Muslem country. Human clinical cases are recorded from non-Muslem islands such as Bali or Irian Jaya which raises the question of immunisation for travellers. Recently, Japanese encephalitis was observed on east of the Wallace line which had been considered as the eastern cut-off line. Malaria is common throughout the country, Plasmodium vivax being the most frequent species. Some of the Anopheline vectors are related to brackish water as are coastal species; others have been favoured by rice growing. Several species bite and rest outdoors, rendering control measures complex. Moreover, chloroquine resistance is increasing in both P. falciparum and P. vivax. All three filaria species responsible for human lymphatic filariasis exist in Indonesia. Bancroft filariasis is present in rather limited foci on most of the islands; malayan filariasis is very prevalent on many islands, mostly in coastal areas, and Timor filariasis exist only on a few small islands. These parasitic diseases are cumulative and do not practically endanger the health of travellers. In the past, plague was common on Java island, but today, human cases are very rare. Scrub typhus is prevalent everywhere, as is murine typhus, being very frequent in harbour cities and one of the main causes of hospitalisation for febrile syndromes.. On the whole, the situation of several of these diseases has been worsening in Indonesia for about thirty years. Although epidemiological situations constantly evolve, two recent occurrences should be paid particular attention: -transmigration which is now a national priority and greatly facilitates the spread of many pathogens, arboviroses or chloroquine-resistant plasmodia, but also of rats, mosquitoes, etc. -deforestation due either to land-farming by Javanese transmigrants or to sudden climatic changes such as El Niño in 1997. Such deep ecological transformations may have considerable and unforeseeable consequences on the epidemiology of vector-borne diseases in Indonesia.