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Memorias do Instituto Oswaldo Cruz2010; 105(6); 829-833; doi: 10.1590/s0074-02762010000600017

Serologic evidence of the recent circulation of Saint Louis encephalitis virus and high prevalence of equine encephalitis viruses in horses in the Nhecolândia sub-region in South Pantanal, Central-West Brazil.

Abstract: As in humans, sub-clinical infection by arboviruses in domestic animals is common; however, its detection only occurs during epizootics and the silent circulation of some arboviruses may remain undetected. The objective of the present paper was to assess the current circulation of arboviruses in the Nhecolândia sub-region of South Pantanal, Brazil. Sera from a total of 135 horses, of which 75 were immunized with bivalent vaccine composed of inactive Eastern equine encephalitis virus (EEEV) and Western equine encephalitis virus(WEEV) and 60 were unvaccinated, were submitted to thorough viral isolation, reverse transcriptase polymerase chain reaction (RT-PCR) and neutralization tests for Saint Louis encephalitis virus (SLEV), EEEV, WEEV and Mayaro virus (MAYV). No virus was isolated and viral nucleic-acid detection by RT-PCR was also negative. Nevertheless, the prevalence of neutralizing antibodies in horses older than seven months was 43.7% for SLEV in equines regardless of vaccine status, and 36.4% for WEEV and 47.7% for EEEV in unvaccinated horses. There was no evidence of MAYV infections. The serologic evidence of circulation of arboviruses responsible for equine and human encephalitis, without recent official reports of clinical infections in the area, suggests that the Nhecolândia sub-region in South Pantanal is an important area for detection of silent activity of arboviruses in Brazil.
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Publication Date: 2010-10-15 PubMed ID: 20945001DOI: 10.1590/s0074-02762010000600017Google Scholar: Lookup
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  • Research Support
  • Non-U.S. Gov't

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.

This study aimed to determine the presence and circulation of arboviruses in the Nhecolândia sub-region of South Pantanal, Brazil. The researchers took samples from 135 horses and looked for past or present infections, by testing for neutralizing antibodies against various strains of encephalitis viruses. The antibody prevalence suggested the silent (sub-clinical or non-symptomatic) circulation of these viruses within the area.

Objective and Methodology

  • The researchers sought to determine the circulation of arboviruses (viruses transmitted by arthropods, such as mosquitoes) in a specific region of Brazil, due to their potential to cause disease in both human and animal populations.
  • 135 horses were tested (75 were pre-immunized and 60 non-vaccinated), through processes of viral isolation, reverse transcriptase polymerase chain reaction (RT-PCR), and neutralization tests.
  • The viruses tested included Saint Louis encephalitis virus (SLEV), Eastern equine encephalitis virus (EEEV), Western equine encephalitis virus (WEEV), and Mayaro virus (MAYV).

Findings

  • No active virus was isolated, and the RT-PCR tests did not detect any viral nucleic-acid.
  • However, they did find a high prevalence of neutralizing antibodies against certain viruses in the sera of the horses. Neutralizing antibodies are a response of the immune system to fight off a specific viral infection, indicating past or present infection.
  • 43.7% of horses, regardless of their vaccination status, had antibodies for SLEV. Among the non-vaccinated horses, 36.4% had antibodies for WEEV and 47.7% for EEEV. No antibodies were detected for MAYV.

Conclusions

  • The presence of these neutralizing antibodies in the absence of reported clinical infections, indicates the silent circulation of these arboviruses in the Nhecolândia sub-region of South Pantanal, Brazil.
  • This ‘silent circulation’ refers to sub-clinical infections where the host is infected with the virus but does not exhibit observable symptoms.
  • The high prevalence of these antibodies, especially in unvaccinated horses, suggests the virus is spreading in the region and underlines the importance of ongoing surveillance in detecting ‘silent’ viral activity.

Cite This Article

APA
Pauvolid-Corrêa A, Tavares FN, Costa EV, Burlandy FM, Murta M, Pellegrin AO, Nogueira MF, Silva EE. (2010). Serologic evidence of the recent circulation of Saint Louis encephalitis virus and high prevalence of equine encephalitis viruses in horses in the Nhecolândia sub-region in South Pantanal, Central-West Brazil. Mem Inst Oswaldo Cruz, 105(6), 829-833. https://doi.org/10.1590/s0074-02762010000600017

Publication

Memorias do Instituto Oswaldo Cruz
ISSN: 1678-8060
NlmUniqueID: 7502619
Country: Brazil
Language: English
Volume: 105
Issue: 6
Pages: 829-833
PII: S0074-02762010000600017

Researcher Affiliations

Pauvolid-Corrêa, Alex
  • Laboratório de Enterovírus, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, RJ, Brazil. pauvolid@ioc.fiocruz.br
Tavares, Fernando Neto
    Costa, Eliane Veiga da
      Burlandy, Fernanda Marcicano
        Murta, Michele
          Pellegrin, Aiesca Oliveira
            Nogueira, Márcia Furlan
              Silva, Edson Elias da

                MeSH Terms

                • Animals
                • Antibodies, Viral / blood
                • Brazil / epidemiology
                • Encephalitis Virus, St. Louis / immunology
                • Encephalitis Virus, St. Louis / isolation & purification
                • Encephalomyelitis, Equine / diagnosis
                • Encephalomyelitis, Equine / epidemiology
                • Encephalomyelitis, Equine / veterinary
                • Encephalomyelitis, Equine / virology
                • Female
                • Horse Diseases / diagnosis
                • Horse Diseases / epidemiology
                • Horses
                • Male
                • Neutralization Tests / veterinary
                • Prevalence
                • Reverse Transcriptase Polymerase Chain Reaction / veterinary
                • Viral Vaccines / administration & dosage

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