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Virology journal2016; 13; 45; doi: 10.1186/s12985-016-0503-9

Characterisation of the epidemic strain of H3N8 equine influenza virus responsible for outbreaks in South America in 2012.

Abstract: An extensive outbreak of equine influenza occurred across multiple countries in South America during 2012. The epidemic was first reported in Chile then spread to Brazil, Uruguay and Argentina, where both vaccinated and unvaccinated animals were affected. In Brazil, infections were widespread within 3months of the first reported cases. Affected horses included animals vaccinated with outdated vaccine antigens, but also with the OIE-recommended Florida clade 1 strain South Africa/4/03. Methods: Equine influenza virus strains from infected horses were isolated in eggs, then a representative strain was subjected to full genome sequencing using segment-specific primers with M13 tags. Phylogenetic analyses of nucleotide sequences were completed using PhyML. Amino acid sequences of haemagglutinin and neuraminidase were compared against those of vaccine strains and recent isolates from America and Uruguay, substitutions were mapped onto 3D protein structures using PyMol. Antigenic analyses were completed by haemagglutination-inhibition assay using post-infection ferret sera. Results: Nucleotide sequences of the haemaglutinin (HA) and neuraminidase (NA) genes of Brazilian isolate A/equine/Rio Grande do Sul/2012 were very similar to those of viruses belonging to Florida clade 1 and clustered with contemporary isolates from the USA. Comparison of their amino acid sequences against the OIE-recommended Florida clade 1 vaccine strain A/equine/South Africa/4/03 revealed five amino acid substitutions in HA and seven in NA. Changes in HA included one within antigenic site A and one within the 220-loop of the sialic acid receptor binding site. However, antigenic analysis by haemagglutination inhibition (HI) assay with ferret antisera raised against representatives of European, Kentucky and Florida sublineages failed to indicate any obvious differences in antigenicity. Conclusions: An extensive outbreak of equine influenza in South America during 2012 was caused by a virus belonging to Florida clade 1, closely related to strains circulating in the USA in 2011. Despite reports of vaccine breakdown with products containing the recommended strain South Africa/03, no evidence was found of significant antigenic drift. Other factors may have contributed to the rapid spread of this virus, including poor control of horse movement.
Publication Date: 2016-03-19 PubMed ID: 26993620PubMed Central: PMC4799594DOI: 10.1186/s12985-016-0503-9Google Scholar: Lookup
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  • Historical Article
  • Journal Article
  • 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.

The research article is about the 2012 outbreak of equine influenza in South America, which was caused by the H3N8 strain of equine influenza virus. This strain greatly affected both vaccinated and unvaccinated animals in Chile, Brazil, Uruguay, and Argentina.

Objective and Methodology:

  • The study aimed to characterize the H3N8 strain of equine influenza virus responsible for the 2012 epidemic in South America and determine the reason for the widespread infection, despite vaccination.
  • Scientists isolated the virus strains from infected horses and subjected representative strains to full genome sequencing. They used PhyML to conduct phylogenetic analyses of nucleotide sequences.
  • To compare the haemagglutinin (HA) and neuraminidase (NA) amino acid sequences of the studied strains with the sequences of vaccine strains and recent isolates, 3D protein structures were analyzed through PyMol.
  • Additionally, antigenic analyses were conducted through a haemagglutination-inhibition (HI) assay using post-infection ferret sera.

Results:

  • Comparison between the sequences of the epidemic strain and the vaccine strains revealed five amino acid substitutions in HA and seven in NA.
  • These alterations included one within antigenic site A and one within the sialic acid receptor binding site on the HA protein.
  • Despite these changes, the HI assay did not show any notable differences in antigenicity, thereby implying that the cause of the epidemic was not a result of significant antigenic drift.

Conclusions:

  • The research concludes that the widespread equine influenza during 2012 was caused by a virus from the Florida clade 1 lineage, closely related to strains that were circulating in the USA in 2011.
  • Despite instances of ineffective vaccination with products containing the recommended OIE strain South Africa/03, it was found that significant antigenic drift was not the causal factor behind the outbreak.
  • Other factors, such as poor control of horse movement, might have played a part in the rapid transmission of the virus.

Cite This Article

APA
Alves Beuttemmüller E, Woodward A, Rash A, Dos Santos Ferraz LE, Fernandes Alfieri A, Alfieri AA, Elton D. (2016). Characterisation of the epidemic strain of H3N8 equine influenza virus responsible for outbreaks in South America in 2012. Virol J, 13, 45. https://doi.org/10.1186/s12985-016-0503-9

Publication

ISSN: 1743-422X
NlmUniqueID: 101231645
Country: England
Language: English
Volume: 13
Pages: 45
PII: 45

Researcher Affiliations

Alves Beuttemmüller, Edsel
  • Universidade Estadual de Londrina, Rodovia Celso Garcia Cid - Pr 445 Km 380, Campus Universitário, Londrina, Paraná, CEP 86057-970, Brazil.
Woodward, Alana
  • Animal Health Trust, Lanwades Park, Kentford, Suffolk, CB8 7UU, UK.
Rash, Adam
  • Animal Health Trust, Lanwades Park, Kentford, Suffolk, CB8 7UU, UK.
Dos Santos Ferraz, Luis Eduardo
  • Laboratórios Vencofarma do Brasil, Travessa Dalva de Oliveira, 237, Londrina, Paraná, CEP 86030-370, Brazil.
Fernandes Alfieri, Alice
  • Universidade Estadual de Londrina, Rodovia Celso Garcia Cid - Pr 445 Km 380, Campus Universitário, Londrina, Paraná, CEP 86057-970, Brazil.
Alfieri, Amauri Alcindo
  • Universidade Estadual de Londrina, Rodovia Celso Garcia Cid - Pr 445 Km 380, Campus Universitário, Londrina, Paraná, CEP 86057-970, Brazil.
Elton, Debra
  • Animal Health Trust, Lanwades Park, Kentford, Suffolk, CB8 7UU, UK. debra.elton@aht.org.uk.

MeSH Terms

  • Amino Acid Sequence
  • Animals
  • Disease Outbreaks
  • Geography, Medical
  • Hemagglutinin Glycoproteins, Influenza Virus / chemistry
  • Hemagglutinin Glycoproteins, Influenza Virus / genetics
  • History, 21st Century
  • Horse Diseases / diagnosis
  • Horse Diseases / epidemiology
  • Horse Diseases / history
  • Horse Diseases / prevention & control
  • Horse Diseases / virology
  • Horses
  • Influenza A Virus, H3N8 Subtype / classification
  • Influenza A Virus, H3N8 Subtype / genetics
  • Influenza A Virus, H3N8 Subtype / immunology
  • Influenza A Virus, H3N8 Subtype / isolation & purification
  • Influenza Vaccines
  • Models, Molecular
  • Molecular Sequence Data
  • Neuraminidase / chemistry
  • Neuraminidase / genetics
  • Orthomyxoviridae Infections / veterinary
  • Phylogeny
  • Protein Conformation
  • RNA, Viral
  • Sequence Alignment
  • South America / epidemiology
  • Vaccination
  • Viral Proteins / chemistry
  • Viral Proteins / genetics

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