The epidemiology of malaria in the Wosera area, East Sepik Province, Papua New Guinea, in preparation for vaccine trials. I. Malariometric indices and immunity

The epidemiological features of malaria were studied through seven community-based surveys in a population of 4000 in the Wosera area, East Sepik Province, Papua New Guinea. Prevalence of parasitaemia (all species, all ages) was 60%. Plasmodium falciparum was the predominant species in all surveys (55%), followed by P. vivax (25%) and P. malariae (20%). The highest prevalence for asexual forms of P. falciparum occurred in the 5-9-year age group, whereas P. falciparum gametocytaemia and P. vivax parasitaemia were observed most frequently in the 1-4-year age group and P. malariae in the 10-15-year age group. Mean densities of all species decreased with age except for that of P. malariae, which was lower in children aged 90% of individuals older than 5 years being positive. Malariological indices showed irregular changes over time but there was no clear-cut seasonal pattern. The geographical distribution of these indices and immune responses was not uniform within the study area. Bednet use and drug consumption were negatively correlated with malariometric indices. Identification of significant temporal and local variations in malaria endemicity is important for the design and evaluation of intervention studies, including field trials of an antimalarial vaccine.