title: Epidemiology and control of frontier malaria in Brazil: lessons from community-based studies in rural Amazonia.
abstract: We describe the epidemiology of malaria in a frontier agricultural settlement in Brazilian Amazonia. We analysed the incidence of slide-confirmed symptomatic infections diagnosed between 2001 and 2006 in a cohort of 531 individuals (2281.53 person-years of follow-up) and parasite prevalence data derived from four cross-sectional surveys. Overall, the incidence rates of Plasmodium vivax and P. falciparum were 20.6/100 and 6.8/100 person-years at risk, respectively, with a marked decline in the incidence of both species (81.4 and 56.8%, respectively) observed between 2001 and 2006. PCR revealed 5.4-fold more infections than conventional microscopy in population-wide cross-sectional surveys carried out between 2004 and 2006 (average prevalence, 11.3 vs. 2.0%). Only 27.2% of PCR-positive (but 73.3% of slide-positive) individuals had symptoms when enrolled, indicating that asymptomatic carriage of low-grade parasitaemias is a common phenomenon in frontier settlements. A circular cluster comprising 22.3% of the households, all situated in the area of most recent occupation, comprised 69.1% of all malaria infections diagnosed during the follow-up, with malaria incidence decreasing exponentially with distance from the cluster centre. By targeting one-quarter of the households, with selective indoor spraying or other house-protection measures, malaria incidence could be reduced by more than two-thirds in this community.
authors.affiliation: Departamento de Parasitologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, Av. Prof. Lineu Prestes 1374, Cidade Universitária, 05508-900 São Paulo, SP, Brazil.
authors.forename: Natal S
authors.initials: NS
authors.lastname: da Silva
authors.forename: M
authors.initials: M
authors.lastname: da Silva-Nunes
authors.forename: Rosely S
authors.initials: RS
authors.lastname: Malafronte
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Menezes
authors.forename: Rosane R
authors.initials: RR
authors.lastname: D'Arcadia
authors.forename: Natália T
authors.initials: NT
authors.lastname: Komatsu
authors.forename: Kézia K G
authors.initials: KK
authors.lastname: Scopel
authors.forename: Erika M
authors.initials: EM
authors.lastname: Braga
authors.forename: Carlos E
authors.initials: CE
authors.lastname: Cavasini
authors.forename: José A
authors.initials: JA
authors.lastname: Cordeiro
authors.forename: Marcelo U
authors.initials: MU
authors.lastname: Ferreira
mesh_terms: D000293:Adolescent; D000328:Adult; D000368:Aged; D000369:Aged, 80 and over; D001938:Brazil / Q000453:epidemiology; D002648:Child; D002675:Child, Preschool; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D016778:Malaria, Falciparum / Q000453:epidemiology* / Q000517:prevention & control; D016780:Malaria, Vivax / Q000453:epidemiology* / Q000517:prevention & control; D008297:Male; D008875:Middle Aged; D010963:Plasmodium falciparum / Q000302:isolation & purification; D010966:Plasmodium vivax / Q000302:isolation & purification; D016133:Polymerase Chain Reaction; D012423:Rural Health; D055815:Young Adult