DYNAMICS OF MALARIA PARASITEMIA ASSOCIATED WITH FEBRILE ILLNESS IN CHILDREN FROM A RURAL AREA OF MADANG, PAPUA-NEW-GUINEA

Active community and self-reporting surveillance techniques have been used to describe the dynamics of febrile illness and associated malari a infection in children aged 2 to 15 years from a rural area of Madang Province, Papua New Guinea (PNG). Both history of fever and fever in association with parasitaemia appeared to be reliable indicators of ma laria morbidity in this endemic area. Parasite density was observed to be a major determinant of mild malarial disease at both the populatio n level and within an individual. Age-specific prevalence of febrile i llness correlated with age-specific patterns of parasite density but n ot of parasite prevalence. Seasonal changes in fever incidence correla ted with parasite density. The transition from afebrile to febrile sta te within an individual was generally associated with an increase in p arasite density. Surveillance and self-reported febrile cases (which d iffer in severity on the basis of the perceived need for treatment) co uld be distinguished on the basis of parasite density. Thus surveillan ce techniques divide clinical malaria in rural PNG into 'mild' and 've ry mild' forms. The age-specific pattern of decline of prevalence of m alaria associated febrile illness and parasite density is best explain ed by induction of strain-specific anti-disease immunity upon infectio n with a given strain of Plasmodium falciparum. The fever threshold in self-reporting febrile cases was seen to decrease with age and can be explained by an age-specific decline in anti-toxic immunity.