Influenza A: detecção de anticorpos e subtipos virais em suínos do Brasil e Estados Unidos

Abstract

In United States, prevalent subtypes of swine influenza A virus (SIAV) include H1N1, H3N2 e H1N2. In Brazil, after H1N1 pandemic outbreak in 2009, serological studies demonstrated circulation of H1N1pdm09, H3N2 and H1N2. The objectives of this study were to detect the presence of antibodies against influenza A in pigs from farms in Brazil and in United States and to detect the presence of influenza virus in nurseling and nursery piglets in vaccinated farms in United States. Thirty farrow-to-finish farms from Minas Gerais state, Brazil, were selected to the serological profile evaluation for H1N1and H3N2 viruses. Four farms from the same production system in Midwest United States with breeding herds vaccinated against influenza were selected and 135 serum samples were collected from 12-17 days old piglets and from all dams corresponding with the piglets. Serum samples were submitted to detection of antibodies against virus nucleoprotein and against virus strains from the vaccine used in the farms. Nasal swabs from the same nurseling piglets and oral fluid from the same group of piglets after transfer to nursery age were collected to detect influenza virus and different subtypes circulating in these ages. Percentage of seronegative piglets and dams varied despite of the vaccination. In Brazil, 26.23% and 1.57% of the animals were seropositive to H1N1pdm09 and H3N2 viruses, respectively, suggesting virus circulation in the farms. H1N2 and H3N2 subtypes were detected in nasal swabs and oral fluid samples from farms in United States. H1N2 virus similar to the vaccine strain virus was isolated from one farm with influenza clinical disease.