Urban malaria in the Brazilian Western Amazon Region I: high prevalence of asymptomatic carriers in an urban riverside district is associated with a high level of clinical malaria.
Cross sectional studies on malaria prevalence was performed in 2001, 2002, and 2004 in Vila Candelária, an urban riverside area of Porto Velho, Rondônia, in the Brazilian Western Amazon, followed by longitudinal surveys on malaria incidence. Vila Candelária is a working class district, provided with electricity, water supply, and basic sanitation. Previous preliminary surveys indicated high malaria incidence in this community. At the end of year 2000 regular diagnostic and treatment measures for malaria were introduced, with active search of febrile cases among residents. Despite of both rapid treatment of cases and relative good sanitary and housing conditions, the malaria incidence persisted at high levels during the following years with an annual parasite index of 150 to 300/1000 inhabitants. Parasite surveys in 2001, 2002, and 2004 achieved through microscopy and polymerase chain reaction to diagnose malaria showed a constant high prevalence of asymptomatic carriers for both Plasmodium falciparum and P. vivax parasites. It was concluded that asymptomatic carriers represent an important reservoirs of parasites and that the carriers might contribute to maintaining the high level of transmission. Comparing our findings to similar geo-demographic situations found in other important urban communities of the Brazilian Amazon, we propose that asymptomatic carriers could explain malaria's outbreaks like the one recently observed in Manaus.
Tada
Mauro Shugiro
MS
Centro de Pesquisa em Medicina Tropical, Porto Velho, RO, Brasil. mauro@ronet.com
Marques
Russimeire Paula
RP
Mesquita
Elieth
E
Dalla Martha
Rosimeire Cristina
RC
Rodrigues
Juan Abel
JA
Costa
Joana D'Arc Neves
JD
Pepelascov
Rosario Rocha
RR
Katsuragawa
Tony Hiroshi
TH
Pereira-da-Silva
Luiz Hildebrando
LH
D000293:Adolescent; D000328:Adult; D001938:Brazil / Q000453:epidemiology; D002353:Carrier State / Q000175:diagnosis / Q000453:epidemiology*; D002648:Child; D002675:Child, Preschool; D004812:Epidemiologic Methods; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D016778:Malaria, Falciparum / Q000175:diagnosis / Q000453:epidemiology*; D016780:Malaria, Vivax / Q000175:diagnosis / Q000453:epidemiology*; D008297:Male; D012621:Seasons; D014505:Urban Population