INFANT PARASITE RATES AND IMMUNOGLOBULIN IN SEROPREVALENCE AS A MEASURE OF EXPOSURE TO PLASMODIUM-FALCIPARUM DURING A RANDOMIZED CONTROLLEDTRIAL OF INSECTICIDE-TREATED BED NETS ON THE KENYAN COAST

Repeated cross-sectional surveys among infants sleeping under insectic ide-treated bed nets (ITBN) and contemporary control infants were used to estimate changes in Plasmodium falciparum exposure due to ITBN use on the Kenyan coast. Presence of P. falciparum parasites or total P. falciparum Immunoglobulin M (IgM) seropositivity were used independent ly and in combination in a constant risk catalytic conversion model to estimate the force of infection in ITBN and control communities. Such studies during infancy avoid problems of early saturation of prevalen ce due to high forces of infection and persistence of infection, minim ize problems of self-treatment, and can be conducted among large popul ations covering a wide geographic area, These contrast previous parasi tologic studies of ITBN among older children and the traditional entom ologic studies of transmission that are logistically demanding. Our in vestigations demonstrated that parasite prevalence, IgM seropositivity , and the force of transmission were all significantly reduced by 50%. In addition, more infants under ITBN entered their second year of lif e without previous exposure to P. falciparum than control infants. The se effects upon delayed acquisition of effective immunity require care ful monitoring during future vector control programs using ITBN.