Epidemiology and control of frontier malaria in Brazil: lessons from community-based studies in rural Amazonia.
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.
da Silva
Natal S
NS
Departamento de Parasitologia, Instituto de Ciências Biomédicas, Universidade de São Paulo, Av. Prof. Lineu Prestes 1374, Cidade Universitária, 05508-900 São Paulo, SP, Brazil.
da Silva-Nunes
M
M
Malafronte
Rosely S
RS
Menezes
Maria J
MJ
D'Arcadia
Rosane R
RR
Komatsu
Natália T
NT
Scopel
Kézia K G
KK
Braga
Erika M
EM
Cavasini
Carlos E
CE
Cordeiro
José A
JA
Ferreira
Marcelo U
MU
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