THE EPIDEMIOLOGY OF MALARIA IN THE WOSERA AREA, EAST SEPIK PROVINCE, PAPUA-NEW-GUINEA, IN PREPARATION FOR VACCINE TRIALS .2. MORTALITY AND MORBIDITY

Malaria mortality and morbidity were studied in a rural population of 4000 in the Wosera area, East Sepik Province, Papua New Guinea, Malari a accounted for 4.9% of the 162 deaths investigated by verbal autopsy and for 12.2% of the 49 deaths assessed through medical records. Malar ia was the first cause of death in children aged 0.5-4 years. Of the 7 795 subjects interviewed and bled during six cross-sectional community -based surveys, children of 1-4 years had the highest malaria-related morbidity. In this age group, point prevalences of fever, fever associ ated with parasitaemia, and fever plus Plasmodium falciparum (Pf) (Pf) parasitaemia greater than or equal to 10000 parasites/mu l blood were 5%, 4.1% and 1.5%, respectively. The corresponding figures for adults were 2%, 0.9% and 0.1%, respectively. The calculation of attributable fraction (AF) using a multiple logistic regression model showed that malaria accounted for 0.44 of all fevers in children of 1-4 years and 0.08 of the fevers in adults. Prevalence data derived from the AF esti mate were compared with those calculated using different accepted dens ity thresholds. The prevalences which best approximated the results fr om the logistic regression model were obtained using parasitaemia cut- offs of greater than or equal to 1000 Pf parasites/mu l in children ag ed 1-4 years and adults older than 19 years and of greater than or equ al to 10000 parasites/mu l in those aged 5-19 years. Prevalence of fev er associated with parasitaemia was highly seasonal, with a peak at th e beginning of the wet season. The geographical distribution of malari a morbidity was not uniform. The measurement of malaria-related morbid ity, the identification of significant seasonal and local variation as well as the assessment of different methods of defining a clinical ep isode of PE malaria are crucial for the design and evaluation of inter vention studies, including field trials of antimalarial vaccines.