EVIDENCE OF SWINE RESPIRATORY INFECTION BY INFLUENZA VIRUSES IN BRAZIL

Abstract

The   global   surveillance   of   influenza, maintained   by   a   network   of   laboratories  sponsored by the World Health Organization, considers pigs as the host responsible for the  interspecies transmission of influenza virus, particularly with regard to the transmission of avian   strains   to   humans.  This   capacity  was   observed   in   1918  when   the  most   tragic influenza pandemic occurred as the consequence of the transmission of the avian influenza strain A(H1N1) to humans,   through  pigs.  This   study was   carried out  with  the   aim of investigating  the potential   level  of   the  influenza  reservoir   in Brazilian pigs.  Either oro-nasal exudates or serum samples were collected from 34 pigs from different regions of Sao Paulo State, BR. These samples were evaluated by two methods: Virus isolation (passage in cell cultures) and the Hemagglutination Inhibition (HI) serological test. Results from the 34 oro-nasal samples obtained by  the virus  isolation method showed that all these pig exudates demonstrated the presence of influenza virus. The serological survey showed that these 34 pig sera samples presented inhibitor antibodies to different influenza virus strains with the distribution of the human influenza A subtypes (H1N1 and H3N2) and type B of 85.29% and 91.17%, respectively. These sera also presented higher percentages (97.05%) of antibodies to specific strains isolated from some of the positive pigs. These data reveal that numerous different influenza virus strains, detected in the Brazilian pig populations, were probably  introduced by avians or  even  through humans,  during  swine husbandry practices. DOI: http://dx.doi.org/10.17525/vrr.v11i1-2.6