Robust estimates of Plasmodium falciparum transmission intensity are imperative for planning, implementation and evaluation of malaria control interventions. Seroconversion rates (SCR) to asexual blood-stage antigens can provide estimates of transmission intensity that correlate with entomological inoculation rates. We study past transmission trends in a rural village and evaluate new models to improve SCR based methods by analysis of antibody levels from multiple cross-sectional serological surveys. The study was conducted in Nyamisati, Rufiji, Tanzania, where parasite prevalence decreased from 65 to 18% from 1999 and 2010. A single intervention with ITNs was performed in 1999. IgG levels to recombinant P. falciparum antigens (MSP-119, MSP-2, MSP-3, AMA-1) and An. gambiae salivary protein gSG6 were measured in children (1-16y) sampled in cross-sectional surveys in 1999 and 2010. SCR and rates of antibody decay were estimated by fitting mathematical models to data from the two cross-sections, assuming three profiles of exposure: (i) stable; (ii) stepwise decrease; or (iii) continuous decrease. Results suggest an average 66% decrease in malaria transmission intensity and an 89% reduction in Anopheles exposure. Transmission trends were best described by a stepwise decrease model with a reduction predicted to occur shortly after distribution of ITNs. The new models provide estimates of the duration of antibody responses under this transmission decline. MSP-119 seropositive individuals were estimated to convert to seronegative with a half-life of 12 (95% CI 7-20) years due to antibody decline with a half-life of 3 (95% CI 2-6) years. The reduction in transmission may in part be attributed to reduced anopheles exposure following the introduction of ITNs, but is not likely to be explained by ITNs alone. Despite reduced parasite prevalence many children remained seropositive to blood-stage antigens. The new sensitive models using antibody levels enabled detection of reduced exposure among seropositive children and provided estimates of both antibody and transmission dynamics
