{"doi":"10.1590/0074-02760220175","title":"Clinically silent Plasmodium vivax infections in native Amazonians of northwestern Brazil: acquired immunity or low parasite virulence?","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.","journal":"Memórias do Instituto Oswaldo Cruz","year":2022,"id":278375,"datarank":0.0,"base_score":0.0,"endowment":0.0,"self_citation_contribution":0.0,"citation_network_contribution":0.0,"self_endowment_contribution":0.0,"citer_contribution":0.0,"corpus_percentile":null,"corpus_rank":null,"citation_count":7,"citer_count":0,"citers_with_citation_signal":0,"citers_with_endowment":0,"datacite_reuse_total":0,"is_dataset":false,"is_dataset_confidence":0.9358,"is_data_producer":false,"deposit_databanks":null,"is_oa":true,"file_count":0,"downloads":0,"has_version_chain":false,"published_date":"2022-01-01","fair_score":null,"fair_percentile":null,"algorithm_id":"datarank_citation_only_1hop_v6","ranking_scope":"data_only","authors":[{"id":906232,"name":"Priscila Rodrigues Calil","orcid":"0000-0002-0018-5936","position":1,"is_corresponding":false},{"id":290862,"name":"Priscila T. Rodrigues","orcid":"0000-0001-5352-6071","position":2,"is_corresponding":false},{"id":707709,"name":"Juliana Tonini","orcid":"0000-0003-2859-9150","position":3,"is_corresponding":false},{"id":951439,"name":"Pablo Secato Fontoura","orcid":null,"position":4,"is_corresponding":false},{"id":951440,"name":"Priscila Moraes Sato","orcid":null,"position":5,"is_corresponding":false},{"id":514901,"name":"Marly Augusto Cardoso","orcid":"0000-0003-0973-3908","position":6,"is_corresponding":false},{"id":951441,"name":"Marina Werneck de Almeida Avellar Russo","orcid":null,"position":7,"is_corresponding":false},{"id":951442,"name":"Carlos Eduardo Cavasini","orcid":null,"position":8,"is_corresponding":false},{"id":951443,"name":"Anderson Rocha de Jesus Fernandes","orcid":null,"position":9,"is_corresponding":false},{"id":290870,"name":"Marcelo U. Ferreira","orcid":"0000-0002-5293-9090","position":10,"is_corresponding":false},{"id":951438,"name":"Luiza Barbosa Barros","orcid":null,"position":0,"is_corresponding":true}],"reference_count":40,"raw_metadata":null,"created_at":"2026-07-19T00:28:47.357993Z","pmid":"36542002","pmcid":null,"fwci":null,"citation_percentile":null,"influential_citations":0,"oa_status":null,"license":null,"views":0,"total_file_size_bytes":0,"version_count":0,"fair_f":null,"fair_a":null,"fair_i":null,"fair_r":null,"fair_zscore":null,"fair_rationale":null,"fair_model":null,"fair_agent_version":null,"fair_fulltext_source":null,"fair_has_llm":null,"fair_computed_at":null,"clinical_trials":[],"software_tools":[],"db_accessions":[],"linked_datasets":[],"topics":[]}