PLASMODIUM-FALCIPARUM MALARIA IN THE FIRST YEAR OF LIFE IN AN AREA OFINTENSE AND PERENNIAL TRANSMISSION

A longitudinal study of Plasmodium falciparum malaria in infants in Id ete village, south-eastern Tanzania, was conducted over a period of 14 months in order to determine the incidence of P. falciparum infection and clinical malaria in the first year of life. Of 1356 blood slides from cross-sectional surveys, 52.1% were positive for asexual stages o f P. falciparum. There were marked increases in P. falciparum prevalen ce, parasite densities, overall fever incidence and the incidence of m alaria fevers with age for the first 6 months of life. The average att ack rate, estimated from a reversible catalytic model, was 0.029 per d ay with a slight increase with age but there was no initial period of protection against infection in neonates. Estimated average duration o f infections was 64 days, with infections in older infants lasting muc h longer than those contracted during the first 2 months of life. Thes e results support the hypotheses that the main effect of passively tra nsferred maternal immunity to malaria is in the control of asexual sta ge parasites, and that the level of clinical immunity depends upon the extent of recent exposure to parasites. Infants as young as 4 months of age are at high risk of clinical attacks. Intervention programmes a gainst malaria in areas of the highest transmission should therefore b e designed to include this group.