HUMAN AND MALARIA PARASITE DIVERSITIES IN RELATION TO THE THERAPEUTIC EFFICACY OF ANTIMALARIALS ON ISLANDS IN THE ASIA AND PACIFIC

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We do the studies of malaria in isolated areas on Island Melanesia in comparison with Sub-Saharan Africa to investigate the interactions among diversities of humans, parasites, mosquitoes and environment to understand relations among transmission, immunity and disease.1.Our studies on merozoite surface protein-1 alleles of P.falciparum in Vanuatu suggested generally limited and stable genetic diversity on islands and a high degree of isolation between the islands, implying that malaria vaccines will be more effective where there is a limited gene pool, as in isolated populations.2.The East Sepik populations of PNG showed a moderate prevalence of CYP2C19-related poor metabolizer (PM), between Island Southeast Asia and Vanuatu, suggesting genetic drift is a main factor of the high prevalence of PM in the Pacific islands.3.In Malawi the switching from chloroquine (CHL) to sulfadoxine/pyrimethamine (SP) in 1993 resulted in a high prevalence rate (78%) of parasites with double dhps and triple dhfr (quintuple) mutations and a reduction in the prevalence of pfcrt K76T (2%) with the recovery of CHL efficacy in 2000. A haplotype analysis revealed that an expansion of wild pfcrt allele is the primary genetic mechanism for the recent recovery of the CHL sensitivity.4.In the highland fringe of Western Kenya our survey showed that anemia was most common in children 【less than or equal】5 years of age (34%) followed by women of childbearing age (16%) in the lowland villages. In children 【less than or equal】5 years, both anemia (ranged from 57% at 1440m to 11% at 2040m) and P.falciparum (from 31% to 0%) prevalence significantly correlated with altitude, suggesting malaria is also the main cause of anemia in the highland fringe areas. Measures that reduce the prevalence of malaria will consequently reduce anemia and the need for blood transfusions associated with the risk of HIV transmission.