title: Serologically defined variations in malaria endemicity in Pará state, Brazil.
abstract: 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 Pará state, Brazilian Amazon region.
  
  
  RESULTS
  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 Anajás, Belém, Goianésia do Pará, Jacareacanga, Itaituba, Trairão, all in the Pará state, and Sucuriju, a free-malaria site in the neighboring state Amapá. 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 (Goianésia do Pará), and are strongly correlated to the corresponding Annual Parasite Index (API). We detected two sites with distinct characteristics: Goianésia do Pará where 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 (Belém) to 0.018 (Goianésia do Pará). We also detected a putative decrease in disease transmission occurred ∼29 years ago in Anajás, Goianésia do Pará, Itaituba, Jacareacanga, and Trairão.
  
  
  CONCLUSIONS
  We observed heterogeneity of serological indices across study sites with different endemicity levels and temporal changes in the force of infection in some of the sites. Our study provides further evidence that serology can be used to measure and monitor transmission of both major species of malaria parasite.
authors.affiliation: Instituto de Ciências Biológicas, Universidade Federal do Pará, Belém, Pará, Brazil; Department of Immunology and Infection, London School of Hygiene & Tropical Medicine, London, United Kingdom.
authors.forename: Maristela G
authors.initials: MG
authors.lastname: Cunha
authors.affiliation: Instituto de Ciências Biológicas, Universidade Federal do Pará, Belém, Pará, Brazil.
authors.forename: Eliane S
authors.initials: ES
authors.lastname: Silva
authors.affiliation: Department of Immunology and Infection, London School of Hygiene & Tropical Medicine, London, United Kingdom; Center of Statistics and Applications, University of Lisbon, Lisbon, Portugal.
authors.forename: Nuno
authors.initials: N
authors.lastname: Sepúlveda
authors.affiliation: Instituto de Ciências Biológicas, Universidade Federal do Pará, Belém, Pará, Brazil.
authors.forename: Sheyla P T
authors.initials: SP
authors.lastname: Costa
authors.affiliation: Instituto de Ciências Biológicas, Universidade Federal do Pará, Belém, Pará, Brazil.
authors.forename: Tiago C
authors.initials: TC
authors.lastname: Saboia
authors.affiliation: Instituto de Ciências Biológicas, Universidade Federal do Pará, Belém, Pará, Brazil.
authors.forename: João F
authors.initials: JF
authors.lastname: Guerreiro
authors.affiliation: Instituto Evandro Chagas, Ananindeua, Pará, Brazil.
authors.forename: Marinete M
authors.initials: MM
authors.lastname: Póvoa
authors.affiliation: Department of Immunology and Infection, London School of Hygiene & Tropical Medicine, London, United Kingdom.
authors.forename: Patrick H
authors.initials: PH
authors.lastname: Corran
authors.affiliation: Department of Immunology and Infection, London School of Hygiene & Tropical Medicine, London, United Kingdom.
authors.forename: Eleanor
authors.initials: E
authors.lastname: Riley
authors.affiliation: Department of Immunology and Infection, London School of Hygiene & Tropical Medicine, London, United Kingdom.
authors.forename: Chris J
authors.initials: CJ
authors.lastname: Drakeley
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D000913:Antibodies, Protozoan / Q000097:blood / Q000276:immunology; D001938:Brazil / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D003430:Cross-Sectional Studies; D019353:Endemic Diseases; D005260:Female; D005843:Geography; D006801:Humans; D007074:Immunoglobulin G / Q000097:blood / Q000276:immunology; D007223:Infant; D007231:Infant, Newborn; D008288:Malaria / Q000453:epidemiology / Q000276:immunology* / Q000469:parasitology; D008297:Male; D020066:Merozoite Surface Protein 1 / Q000276:immunology; D008875:Middle Aged; D010963:Plasmodium falciparum / Q000276:immunology* / Q000502:physiology; D010966:Plasmodium vivax / Q000276:immunology* / Q000502:physiology; D015995:Prevalence; D016036:Seroepidemiologic Studies; D055815:Young Adult
chemical_list: D000913:Antibodies, Protozoan; D007074:Immunoglobulin G; D020066:Merozoite Surface Protein 1