7 research outputs found
Asymptomatic infection with Plasmodium falciparum and Plasmodium vivax in the Brazilian Amazon Basin: to treat or not to treat?
In this study, we determined whether the treatment of asymptomatic parasites carriers (APCs), which are frequently found in the riverside localities of the Brazilian Amazon that are highly endemic for malaria, would decrease the local malaria incidence by decreasing the overall pool of parasites available to infect mosquitoes. In one village, the treatment of the 19 Plasmodium falciparum-infected APCs identified among the 270 residents led to a clear reduction (Z = -2.39, p = 0.017) in the incidence of clinical cases, suggesting that treatment of APCs is useful for controlling falciparum malaria. For vivax malaria, 120 APCs were identified among the 716 residents living in five villages. Comparing the monthly incidence of vivax malaria in two villages where the APCs were treated with the incidence in two villages where APCs were not treated yielded contradictory results and no clear differences in the incidence were observed (Z = -0.09, p = 0.933). Interestingly, a follow-up study showed that the frequency of clinical relapse in both the treated and untreated APCs was similar to the frequency seen in patients treated for primary clinical infections, thus indicating that vivax clinical immunity in the population is not species specific but only strain specific
Microsatellite characterization of Plasmodium falciparum from symptomatic and non-symptomatic infections from the Western Amazon reveals the existence of non-symptomatic infection-associated genotypes
Microsatellite characterization of Plasmodium falciparum from symptomatic and non-symptomatic infections from the Western Amazon reveals the existence of non-symptomatic infection-associated genotypes
In Western Amazon areas with perennial malaria transmission, long term
residents frequently develop partial immunity to malarial infection
caused either by Plasmodium falciparum or P. vivax, resulting in a
considerable number of non-symptomatically infected individuals. For
yet unknown reasons, these individuals sporadically develop symptomatic
malaria. In order to identify if determined parasite genotypes, defined
by a combination of eleven microsatellite markers, were associated to
different outcomes symptomatic or asymptomatic malaria we analyzed
infecting P. falciparum parasites in a suburban riverine population.
Despite of detecting a high degree of diversity in the analyzed
samples, several microsatellite marker alleles appeared accumulated in
parasites from non-symptomatic infections. This result may be
interpreted that a number of microsatellites, which are not directly
related to antigenic features, could be associated to the outcome of
malarial infection. The result may also point to a low frequency of
recombinatorial events which otherwise would dissociate genes under
strong immune pressure from the relatively neutral microsatellite loci
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
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 200