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Memorias do Instituto Oswaldo Cruz2025; 120; e240218; doi: 10.1590/0074-027602402180

Orthoflavivirus nilense surveillance in the State of Piauí, northeastern Brazil.

Abstract: The cycle of the Orthoflavivirus nilense (West Nile virus - WNV) involves birds and mosquitoes, while humans and equids serve as terminal hosts. In 2014, the first human case in Brazil was confirmed in Piauí State. Objective: To investigate the presence of WNV in birds, mosquitoes, and equids in municipalities of Piauí. Methods: Collections were carried out following recommendations from the Ministry of Health of Brazil, in 11 municipalities (all with human cases or bird mortality), where biological samples were collected from birds, mosquitoes, and equids. The Viral RNA extraction was performed using a commercial kit, following the manufacturers' recommendations; samples were subjected to reverse transcription and polymerase chain reaction, with specific primers for WNV. Results: 2,706 samples were collected (636 birds, belonging to 99 species; 420 equids, and 1,650 mosquitoes, grouped into 346 pools, totaling 18 species. No collected sample yielded a positive result, corroborating with other studies showing the difficulty of molecular detection of WNV in healthy animals, which may explain the non-detection, in addition to the delayed diagnosis in humans. Conclusions: A local investigation involving suspected cases is still recommended in animals; however, in locations with late diagnosis in humans we suggest a serological survey of asymptomatic birds and equids.
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Publication Date: 2025-07-07 PubMed ID: 40638500PubMed Central: PMC12237142DOI: 10.1590/0074-027602402180Google Scholar: Lookup
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  • Journal Article

Summary

This research summary has been generated with artificial intelligence and may contain errors and omissions. Refer to the original study to confirm details provided. Submit correction.

Overview

  • This study aimed to detect the presence of West Nile virus (WNV), known as Orthoflavivirus nilense, in birds, mosquitoes, and equids in the northeastern Brazilian state of Piauí, an area with previously reported human cases.
  • The researchers collected biological samples from multiple species and tested them for WNV but found no positive cases, highlighting challenges in molecular detection and suggesting alternative surveillance approaches.

Research Context and Objective

  • WNV is a virus transmitted primarily between birds and mosquitoes, with humans and equids (horses and related species) serving as incidental or terminal hosts.
  • In 2014, Piauí State confirmed the first human case of WNV infection in Brazil, increasing the need for surveillance in the region to understand viral circulation.
  • The main objective was to investigate whether WNV is present in vectors (mosquitoes) and hosts (birds and equids) in specific municipalities of Piauí where human cases or bird deaths have been reported.

Methods

  • Sampling was conducted in 11 municipalities selected due to WNV-related factors (presence of human cases or bird mortality).
  • Birds, mosquitoes, and equids were systematically sampled according to guidelines recommended by Brazil’s Ministry of Health.
  • Biological samples included:
    • 636 birds from 99 species.
    • 420 equids.
    • 1,650 mosquitoes pooled into 346 groups, representing 18 species.
  • Laboratory testing involved:
    • Extraction of viral RNA using commercial kits per manufacturer instructions.
    • Reverse transcription to convert RNA into complementary DNA.
    • Polymerase chain reaction (PCR) with WNV-specific primers to amplify viral genetic material for detection.

Results

  • No samples from birds, mosquitoes, or equids tested positive for WNV RNA.
  • The absence of molecular detection aligns with previous studies suggesting:
    • WNV is difficult to detect molecularly in apparently healthy animals, as viral RNA may be present only transiently or at low levels.
    • Delays between animal infection and sample collection reduce chances of positive viral RNA detection.
    • Late diagnoses in human cases further complicate linking animal infections to human outbreaks.

Conclusions and Recommendations

  • While no WNV RNA was found, the study recommends continuing local investigations when suspected cases appear in animals to monitor viral activity.
  • In locations where human diagnosis is often delayed, molecular testing may not be effective due to timing issues.
  • Instead, the authors propose serological surveys that detect antibodies against WNV in asymptomatic birds and equids, which can reveal past exposure rather than active infection.
  • This approach could provide valuable epidemiological information to understand WNV circulation patterns and help prevent outbreaks.

Cite This Article

APA
Lobato OL, Nogueira TDS, Lima TET, Andrade FJDC, de Macedo MGG, Pereira RS, Xavier J, Amorim MR, Barbosa PP, da Rocha AS, Silva SDC, Alcantara LCJ, de Souza WM, Proenca-Modena JL, Costa ÉA, Lima Neto AS, Feitosa LCS, Pires E Cruz MDS, Silva SMMS, Baêta SAF, Vieira MADCES, Deem SL, Catenacci LS. (2025). Orthoflavivirus nilense surveillance in the State of Piauí, northeastern Brazil. Mem Inst Oswaldo Cruz, 120, e240218. https://doi.org/10.1590/0074-027602402180

Publication

Memorias do Instituto Oswaldo Cruz
ISSN: 1678-8060
NlmUniqueID: 7502619
Country: Brazil
Language: English
Volume: 120
Pages: e240218
PII: e240218

Researcher Affiliations

Lobato, Osmaikon Lisboa
  • Universidade Federal do Piauí, Centro de Ciências Agrárias, Teresina, PI, Brasil.
  • Universidade Federal do Piauí, Programa de Pós-Graduação em Tecnologias Aplicadas a Animais de Interesse Regional, Teresina, PI, Brasil.
Nogueira, Tayná da Silva
  • Universidade Federal do Piauí, Bom Jesus, PI, Brasil.
Lima, Tobias Emílio Tavares
  • Universidade Federal do Piauí, Bom Jesus, PI, Brasil.
Andrade, Felipe José da Costa
  • Universidade Federal do Piauí, Bom Jesus, PI, Brasil.
de Macedo, Marília Gabryelle Guimarães
  • Universidade Federal do Piauí, Bom Jesus, PI, Brasil.
Pereira, Rayane de Souza
  • Universidade Federal do Oeste da Bahia, Programa de Pós-Graduação em Ciências Ambientais, Barreiras, BA, Brasil.
Xavier, Joilson
  • Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brasil.
Amorim, Mariene Ribeiro
  • Universidade Estadual de Campinas, Instituto de Biologia, Departamento de Genética, Evolução, Microbiologia e Imunologia, Campinas, SP, Brasil.
Barbosa, Priscilla Paschoal
  • Universidade Estadual de Campinas, Instituto de Biologia, Departamento de Genética, Evolução, Microbiologia e Imunologia, Campinas, SP, Brasil.
da Rocha, Alex Sobrinho
  • Universidade Federal do Piauí, Bom Jesus, PI, Brasil.
Silva, Silvokleio da Costa
  • Universidade Federal do Piauí, Bom Jesus, PI, Brasil.
Alcantara, Luiz Carlos Junior
  • Fundação Oswaldo Cruz-Fiocruz, Instituto René Rachou, Belo Horizonte, MG, Brasil.
de Souza, William M
  • University of Texas Medical Branch, Department of Microbiology and Immunology, Galveston, TX, USA.
  • University of Texas Medical Branch, World Reference Center for Emerging Viruses and Arboviruses, Galveston, TX, USA.
Proenca-Modena, José Luiz
  • Universidade Estadual de Campinas, Instituto de Biologia, Departamento de Genética, Evolução, Microbiologia e Imunologia, Campinas, SP, Brasil.
Costa, Érica Azevedo
  • Universidade Federal de Minas Gerais, Belo Horizonte, MG, Brasil.
Lima Neto, Adelino Soares
  • Laboratório Central de Saúde Pública do Piauí, Teresina, PI, Brasil.
Feitosa, Lauro César Soares
  • Universidade Federal do Piauí, Centro de Ciências Agrárias, Teresina, PI, Brasil.
Pires E Cruz, Maria do Socorro
  • Universidade Federal do Piauí, Centro de Ciências Agrárias, Teresina, PI, Brasil.
Silva, Silvana Maria Medeiros de Sousa
  • Universidade Federal do Piauí, Centro de Ciências Agrárias, Teresina, PI, Brasil.
Baêta, Silvia de Araújo França
  • Universidade Federal do Piauí, Centro de Ciências Agrárias, Teresina, PI, Brasil.
Vieira, Marcelo Adriano da Cunha E Silva
  • Instituto de Doenças Tropicais Natan Portella, Teresina, PI, Brasil.
Deem, Sharon L
  • Institute for Conservation Medicine, Saint Louis Zoo, St Louis, Missouri, USA.
Catenacci, Lilian Silva
  • Universidade Federal do Piauí, Centro de Ciências Agrárias, Teresina, PI, Brasil.
  • Universidade Federal do Piauí, Programa de Pós-Graduação em Tecnologias Aplicadas a Animais de Interesse Regional, Teresina, PI, Brasil.
  • Institute for Conservation Medicine, Saint Louis Zoo, St Louis, Missouri, USA.
  • Centro de Inteligência em Agravos Tropicais Emergentes e Negligenciados, Teresina, PI, Brasil.
  • Universidade Federal do Pará, Programa de Pós-Graduação em Saúde Animal na Amazônia, Castanhal, PA, Brasil.

MeSH Terms

  • Animals
  • Brazil / epidemiology
  • West Nile virus / isolation & purification
  • West Nile virus / genetics
  • Culicidae / virology
  • Equidae / virology
  • Birds / virology
  • RNA, Viral / analysis
  • Reverse Transcriptase Polymerase Chain Reaction
  • Humans
  • West Nile Fever / epidemiology
  • West Nile Fever / veterinary
  • Horses

Conflict of Interest Statement

The authors declare no conflict of interest

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