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(Reference retrieved automatically from SciELO through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Clinically silent Plasmodium vivax infections in native Amazonians of northwestern Brazil: acquired immunity or low parasite virulence?

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Author(s):
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Luiza Barbosa Barros [1] ; Priscila Rodrigues Calil [2] ; Priscila Thihara Rodrigues [3] ; Juliana Tonini [4] ; Pablo Secato Fontoura [5] ; Priscila Moraes Sato [6] ; Marly Augusto Cardoso [7] ; Marina Werneck de Almeida Avellar Russo [8] ; Carlos Eduardo Cavasini [9] ; Anderson Rocha de Jesus Fernandes [10] ; Marcelo Urbano Ferreira
Total Authors: 11
Affiliation:
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[1] Universidade de São Paulo. Instituto de Ciências Biomédicas. Departamento de Parasitologia - Brasil
[2] Universidade de São Paulo. Instituto de Ciências Biomédicas. Departamento de Parasitologia - Brasil
[3] Universidade de São Paulo. Instituto de Ciências Biomédicas. Departamento de Parasitologia - Brasil
[4] Universidade de São Paulo. Instituto de Ciências Biomédicas. Departamento de Parasitologia - Brasil
[5] Universidade de São Paulo. Instituto de Ciências Biomédicas. Departamento de Parasitologia - Brasil
[6] Universidade de São Paulo. Faculdade de Saúde Pública. Departamento de Nutrição - Brasil
[7] Universidade de São Paulo. Faculdade de Saúde Pública. Departamento de Nutrição - Brasil
[8] Universidade de São Paulo. Instituto de Ciências Biomédicas. Departamento de Parasitologia - Brasil
[9] Faculdade de Medicina de São José do Rio Preto. Departamento de Doenças Dermatológicas, Infecciosas e Parasitárias - Brasil
[10] Universidade de São Paulo. Instituto de Ciências Biomédicas. Departamento de Parasitologia - Brasil
Total Affiliations: 11
Document type: Journal article
Source: Memórias do Instituto Oswaldo Cruz; v. 117, 2022-12-16.
Abstract

BACKGROUND Malaria remains common among native Amazonians, challenging Brazil′s elimination efforts. OBJECTIVES We examined the epidemiology of malaria in riverine populations of the country′s main hotspot - the upper Juruá Valley in Acre state, close to the Brazil-Peru border, where Plasmodium vivax accounts for > 80% of cases. METHODS Participants (n = 262) from 10 villages along the Azul River were screened for malaria parasites by microscopy and genus-specific, cytochrome b (cytb) gene-based polymerase chain reaction. Positive samples were further tested with quantitative TaqMan assays targeting P. vivax- and P. falciparum-specific cytb domains. We used multiple logistic regression analysis to identify independent correlates of P. vivax infection. FINDINGS Microscopy detected only one P. vivax and two P. falciparum infections. TaqMan assays detected 33 P. vivax infections (prevalence, 11.1%), 78.1% of which asymptomatic, with a median parasitaemia of 34/mL. Increasing age, male sex and use of insecticide-treated bed nets were significant predictors of elevated P. vivax malaria risk. Children and adults were similarly likely to remain asymptomatic once infected. MAIN CONCLUSIONS Our findings are at odds with the hypothesis of age-related clinical immunity in native Amazonians. The low virulence of local parasites is suggested as an alternative explanation for subclinical infections in isolated populations. (AU)

FAPESP's process: 16/18740-9 - Scientific bases for residual malaria elimination in the Brazilian Amazon
Grantee:Marcelo Urbano Ferreira
Support Opportunities: Research Projects - Thematic Grants