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Equine veterinary journal2019; 52(3); 420-427; doi: 10.1111/evj.13176

Multifocal outbreak of equine influenza in vaccinated horses in Argentina in 2018: Epidemiological aspects and molecular characterisation of the involved virus strains.

Abstract: Equine influenza is an important cause of respiratory disease of horses worldwide. The equine influenza virus (EIV) undergoes antigenic drift through the accumulation of amino acid substitutions in the viral proteins, which may lead to vaccine breakdown. Objective: To describe the epidemiological findings and the molecular characteristics of the EIV detected during the multifocal outbreak that occurred in Argentina between March and July 2018 and evidence a vaccine breakdown. Methods: Observational, descriptive study. Methods: Virus was detected in nasopharyngeal swabs using real-time reverse transcriptase PCR (RT-PCR). Nucleotide and deduced amino acid sequences of the haemagglutinin (HA) and neuraminidase (NA) genes were obtained from EIV positive nasopharyngeal swabs, and phylogenetic analysis was undertaken. Amino acid sequences were compared against the current World Organisation for Animal Health (OIE)-recommended Florida clade 1 vaccine strain and strain components of vaccines used in Argentina. Serum samples were tested using haemagglutination inhibition test. Results: Equine influenza virus infection was confirmed using real-time RT-PCR and serological testing. The phylogenetic analysis of the HA and NA genes revealed that all the EIV identified during the outbreak belong to the H3N8 subtype, Florida clade 1. Multiple amino acid changes, some of them at antigenic sites, were observed in the circulating virus when compared with the strains included in the most commonly used vaccine in Argentina. Seventy-six percent of the affected horses had been vaccinated with this vaccine, suggesting the occurrence of vaccine breakdown. Conclusions: The study does not include antigenic characterisation and full genome sequencing of Argentinian strains, that could provide additional information. Conclusions: The occurrence of this multifocal equine influenza outbreak in regularly vaccinated horses is a field evidence of vaccine breakdown, reinforcing the necessity of keeping vaccine strains updated according to OIE recommendations. It also underlines the importance of the implementation of appropriate quarantine measures and restriction of horse movement in the face of disease.
© 2019 EVJ Ltd.
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Publication Date: 2019-10-04 PubMed ID: 31494962DOI: 10.1111/evj.13176Google Scholar: Lookup
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  • Journal Article
  • Observational Study
  • Veterinary

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.

The research discusses a major outbreak of equine influenza in horses in Argentina in 2018, focusing on an epidemiological study and molecular characterisation of the strains involved. Despite widespread immunisation, a high percentage of vaccinated horses were affected, suggestive of potential issues with the vaccine.

Research Objective and Methodology

  • The goal of this study was to understand the epidemiological aspects and molecular characteristics of the equine influenza virus (EIV) during the large-scale outbreak that took place in Argentina from March to July 2018.
  • To identify the virus, real-time reverse transcriptase PCR (RT-PCR) was applied to nasopharyngeal swabs taken from the horses.
  • The researchers carried out phylogenetic analysis on the nucleotide and deduced amino acid sequences of the haemagglutinin (HA) and neuraminidase (NA) genes from the EIV positive swabs.
  • They compared the amino acid sequences against the current OIE (World Organisation for Animal Health)-recommended Florida clade 1 vaccine strain and other strains used in Argentinean vaccines.
  • Serum samples from the horses were tested using the haemagglutination inhibition test to confirm the presence of EIV infection.

Results of the Research

  • The study confirmed the presence of EIV infection in the horses using the real-time RT-PCR technique and serological testing.
  • According to the phylogenetic analysis, all the identified EIV belonged to the H3N8 subtype, Florida clade 1.
  • There were multiple alterations in the amino acid sequence in the circulating virus when compared with the strains in the most commonly administered vaccine in Argentina.
  • Despite being vaccinated with this vaccine, seventy-six percent of the affected horses were infected, thereby indicating a potential vaccine breakdown.

Conclusions

  • The study is limited in that it does not include antigenic characterisation and full genome sequencing of the Argentinian strains, which could add more insight to the findings.
  • However, the findings of the research highlight the problem of a vaccine breakdown, emphasising the need for ongoing updates of vaccine strains, in line with OIE recommendations.
  • The study also underscores the essential role of proper quarantine protocols and restrictions on horse movement to prevent the disease from spreading.

Cite This Article

APA
Olguin-Perglione C, Vissani MA, Alamos F, Tordoya MS, Barrandeguy M. (2019). Multifocal outbreak of equine influenza in vaccinated horses in Argentina in 2018: Epidemiological aspects and molecular characterisation of the involved virus strains. Equine Vet J, 52(3), 420-427. https://doi.org/10.1111/evj.13176

Publication

Equine veterinary journal
ISSN: 2042-3306
NlmUniqueID: 0173320
Country: United States
Language: English
Volume: 52
Issue: 3
Pages: 420-427

Researcher Affiliations

Olguin-Perglione, C
  • Instituto de Virología, Instituto Nacional de Tecnología Agropecuaria (INTA), Hurlingham, Buenos Aires, Argentina.
Vissani, M A
  • Instituto de Virología, Instituto Nacional de Tecnología Agropecuaria (INTA), Hurlingham, Buenos Aires, Argentina.
  • Escuela de Veterinaria, Universidad del Salvador, Pilar, Buenos Aires, Argentina.
Alamos, F
  • Instituto de Virología, Instituto Nacional de Tecnología Agropecuaria (INTA), Hurlingham, Buenos Aires, Argentina.
Tordoya, M S
  • Instituto de Virología, Instituto Nacional de Tecnología Agropecuaria (INTA), Hurlingham, Buenos Aires, Argentina.
Barrandeguy, M
  • Instituto de Virología, Instituto Nacional de Tecnología Agropecuaria (INTA), Hurlingham, Buenos Aires, Argentina.
  • Escuela de Veterinaria, Universidad del Salvador, Pilar, Buenos Aires, Argentina.

MeSH Terms

  • Animals
  • Argentina
  • Disease Outbreaks
  • Horse Diseases / epidemiology
  • Horse Diseases / virology
  • Horses
  • Influenza A Virus, H3N8 Subtype
  • Orthomyxoviridae Infections / epidemiology
  • Orthomyxoviridae Infections / veterinary
  • Phylogeny

Grant Funding

  • Instituto Nacional de Tecnología Agropecuaria (INTA)
  • INTA-Haras Agreement

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Citations

This article has been cited 12 times.
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