Outbreak of equine influenza caused by influenza virus A/equi 1 in the State of Rio de Janeiro, Brazil
Cunha, R.G.; da Silva Passos, W.; Correa do Valle, M.D.
Revista Brasileira de Biologia 38(3): 549-554
1978
ISSN/ISBN: 0034-7108 PMID: 211560 Document Number: 127341
An outbreak of respiratory disease in horses was reported in the counties of Rio de Janeiro and Campos, Brazil. Nasal mucus from 11 horses was collected on sterile swabs and inoculated separately into groups of 11 day old embryonated eggs for virus isolation. One material, harvested at Jockey Club, Rio de Janeiro, yielded an agent that agglutinated chicken red cells. Hemagglutination inhibition (HAI) tests were performed to identify the new isolated strain--RJ/76. Homologous and A/equine/Praga/1/56 (Heq 1 Neq 1) immune sera inhibited the Ha induced by the RJ/76 strain. These sera inhibited the hemagglutination activity of the A/equine/Praga/1/56 strain. Negative results were shown by A/equine/Miami/1/63 (Heq 2 Neq 2), A/Hong Kong/1/68 (H3 N2) and Newcastle disease immune sera. Pairs of serum (17) collected in the Campos area from horses that exhibited clinical signs of respiratory disease were examined by HAI test. For the 1st sera, 10 of 17 were negative and 7 showed antibodies at low levels for RJ/76 and A/Equi 1 strains. For the 2nd sera, all 17 revealed high levels of antibodies for these virus strains. Equine sera (20) collected at Jockey Club, Rio de Janeiro, from convalescent animals showed high levels of antibodies for RJ/76 and A/Equi 1/Praga virus strains. All sera from Campos and Rio de Janeiro were negative for A/Equi 2 subtype of influenza virus. The virus isolation, its cross-reaction with A/equi/1/Praga virus and the results of the equine sera examination suggest that the present outbreak of respiratory disease was caused by subtype A/Equi 1 of influenza virus.