MALARIA EPIDEMIOLOGY, GLUCOSE-6-PHOSPHATE-DEHYDROGENASE DEFICIENCY AND HUMAN SETTLEMENT IN THE VANUATU ARCHIPELAGO

Vanuatu is located at the southeast margin of the malarious band exten ding from southeast Asia to eastern Melanesia. We analysed the malaria situation on different islands of Vanuatu, using passive case detecti on and malariometric survey data from 1985 to 1992, i.e. after the DDT residual programme ceased and before the impregnated bed-nets program me started on a larger scale. Malaria was mainly hypo-mesoendemic but with hyperendemic spots in certain years and on some islands. The tran smission was generally more intense in the northern islands than in th e south. In the late 1980s, annual parasite incidence per one thounsan d population (API) was around 180. The overall parasite rate was 11.9% with Plasmodium falciparum, P. vivax and P. malariae rate of 5.2, 6.7 . and 0.1%, respectively. There was a seasonal fluctuation of P. Jalci parum incidence, whereas the P. vivax incidence was rather stable. Viv ax malaria was confined to children less than 10 years old, while the intense in the northern islands than in the south. In the late 1980s, annual parasite incidence per one thousand population (API) was around 180. The overall parasite rate was 11.9% with Plasmodium falciparum, P. vivax and P. malariae rate of 5.2, 6.7, and 0.1%, respectively. The re was a seasonal fluctuation of P, falciparum incidence, whereas the P. vivax incidenceprevalence of P. falciparum only changed moderately with age. The mean rate of glucose 6-phosphate dehydrogenase (G6PD) de ficiency among male subjects was in 7.4% but with a wide variation of 0-14.3% on different islands. A positive rank-order correlation was fo und between malaria incidence and G6PD deficiency rate on the differen t islands, A reasonable hypothesis is that malaria was introduced to t he islands with the first human settlement 4000 years ago, with a geog raphical malaria distribution similar to the present situation. Differ ent malaria endemicities possibly then selected different prevalences of G6PD deficiency over many generations. (C) 1998 Elsevier Science B. V. All rights reserved.