Brazilian Journal of Microbiology Brazilian Journal of Microbiology
Braz J Microbiol 2018;49:336-46 - Vol. 49 Num.2 DOI: 10.1016/j.bjm.2017.07.003
Veterinary Microbiology
Evolution of equine influenza viruses (H3N8) during a Brazilian outbreak, 2015
Patricia Filippsen Favaroa,, , Wilson Roberto Fernandesb, Dilmara Reischakc, Paulo Eduardo Brandãoa, Sheila Oliveira de Souza Silvaa, Leonardo José Richtzenhaina
a Universidade de São Paulo, Faculdade de Medicina Veterinária e Zootecnia, Departamento de Medicina Veterinária Preventiva e Saúde Animal, São Paulo, SP, Brazil
b Universidade de São Paulo, Faculdade de Medicina Veterinária e Zootecnia, Departamento de Clínica Médica, São Paulo, SP, Brazil
c Ministério da Agricultura, Pecuária e Abastecimento, Laboratório Nacional Agropecuário, Campinas, SP, Brazil
Received 17 January 2017, Accepted 07 July 2017
Abstract

Equine influenza is one of the major respiratory infectious diseases in horses. An equine influenza virus outbreak was identified in vaccinated and unvaccinated horses in a veterinary school hospital in São Paulo, SP, Brazil, in September 2015. The twelve equine influenza viruses isolated belonged to Florida Clade 1. The hemagglutinin and neuraminidase amino acid sequences were compared with the recent isolates from North and South America and the World Organisation for Animal Health recommended Florida Clade 1 vaccine strain. The hemagglutinin amino acid sequences had nine substitutions, compared with the vaccine strain. Two of them were in antigenic site A (A138S and G142R), one in antigenic site E (R62K) and another not in antigenic site (K304E). The four substitutions changed the hydrophobicity of hemagglutinin. Three distinct genetic variants were identified during the outbreak. Eleven variants were found in four quasispecies, which suggests the equine influenza virus evolved during the outbreak. The use of an out of date vaccine strain or updated vaccines without the production of protective antibody titers might be the major contributing factors on virus dissemination during this outbreak.

Keywords
Equine influenza, H3N8, Hemagglutinin, Neuraminidase, Evolutionary analysis
Braz J Microbiol 2018;49:336-46 - Vol. 49 Num.2 DOI: 10.1016/j.bjm.2017.07.003
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