Serologically Defined Variations in Malaria Endemicity in Pará State, Brazil

Background: Measurement of malaria endemicity is typically based on vector or parasite measures. A complementary approach is the detection of parasite specific IgG antibodies. We determined the antibody levels and seroconversion rates to both P. vivax and P. falciparum merozoite antigens in individuals living in areas of varying P. vivax endemicity in Parastate, Brazilian Amazon region. Methodology/Principal Findings: The prevalence of antibodies to recombinant antigens from P. vivax and P. falciparum was determined in 1,330 individuals. Cross sectional surveys were conducted in the north of Brazil in Anajas, Belem, Goianesia do Para ´ , Jacareacanga, Itaituba, Trairao, all in the Parastate, and Sucuriju, a free- malaria site in the neighboring state Amapa ´ . Seroprevalence to any P. vivax antigens (MSP1 or AMA-1) was 52.5%, whereas 24.7% of the individuals were seropositive to any P. falciparum antigens (MSP1 or AMA-1). For P. vivax antigens, the seroconversion rates (SCR) ranged from 0.005 (Sucuriju) to 0.201 (Goianesia do Para ´ ), and are strongly correlated to the corresponding Annual Parasite Index (API). We detected two sites with distinct characteristics: Goianesia do Parawhere seroprevalence curve does not change with age, and Sucuriju where seroprevalence curve is better described by a model with two SCRs compatible with a decrease in force of infection occurred 14 years ago (from 0.069 to 0.005). For P. falciparum antigens, current SCR estimates varied from 0.002 (Belem ) to 0.018 (Goianesia do Para ´ ). We also detected a putative decrease in disease transmission occurred ,29 years ago in Anajas, Goianesia do Para ´ , Itaituba, Jacareacanga, and Trairao . Conclusions: We observed heterogeneity of serological indices across study sites with different endemicity levels and temporal changes in the force of infection in