RESUMO
Influenza, a zoonosis caused by various influenza A virus subtypes, affects a wide range of species, including humans. Pig cells express both sialyl-α-2,3-Gal and sialyl-α-2,6-Gal receptors, which make them susceptible to infection by avian and human viruses, respectively. To date, it is not known whether wild pigs in Mexico are affected by influenza virus subtypes, nor whether this would make them a potential risk of influenza transmission to humans. In this work, 61 hogs from two municipalities in Campeche, Mexico, were sampled. Hemagglutination inhibition assays were performed in 61 serum samples, and positive results were found for human H1N1 (11.47%), swine H1N1 (8.19%), and avian H5N2 (1.63%) virus variants. qRT-PCR assays were performed on the nasal swab, tracheal, and lung samples, and 19.67% of all hogs were positive to these assays. An avian H5N2 virus, first reported in 1994, was identified by sequencing. Our results demonstrate that wild pigs are participating in the exposure, transmission, maintenance, and possible diversification of influenza viruses in fragmented habitats, highlighting the synanthropic behavior of this species, which has been poorly studied in Mexico.
Assuntos
Vírus da Influenza A/isolamento & purificação , Influenza Humana/transmissão , Influenza Humana/virologia , Infecções por Orthomyxoviridae/veterinária , Doenças dos Suínos/virologia , Animais , Animais Selvagens/virologia , Testes de Inibição da Hemaglutinação , Humanos , Vírus da Influenza A Subtipo H1N1/classificação , Vírus da Influenza A Subtipo H1N1/genética , Vírus da Influenza A Subtipo H1N1/isolamento & purificação , Vírus da Influenza A Subtipo H5N2/classificação , Vírus da Influenza A Subtipo H5N2/genética , Vírus da Influenza A Subtipo H5N2/isolamento & purificação , Vírus da Influenza A/classificação , Vírus da Influenza A/genética , Influenza Humana/epidemiologia , Pulmão/patologia , Pulmão/virologia , México/epidemiologia , Infecções por Orthomyxoviridae/epidemiologia , Infecções por Orthomyxoviridae/patologia , Infecções por Orthomyxoviridae/virologia , Suínos , Doenças dos Suínos/epidemiologia , Doenças dos Suínos/patologia , Doenças dos Suínos/transmissão , Traqueia/patologia , Traqueia/virologia , Zoonoses/epidemiologia , Zoonoses/transmissão , Zoonoses/virologiaRESUMO
BACKGROUND: Serologic surveillance of Avian Influenza (AI) viruses is carried out by the hemagglutination inhibition (HI) test using reference reagents. This method is recommended by animal health organizations as a standard test to detect antigenic differences (subtypes) between circulating influenza virus, vaccine- and/or reference- strains. However, significant discrepancies between reference antisera and field isolates have been observed during serosurveillance of influenza A viruses in pig and poultry farms. The objective of this study was to examine the effects of influenza virus genetic and antigenic drift on serologic testing using standard HI assays and reference reagents. Low pathogenic AI H5N2 viruses isolated in Mexico between 1994 and 2008 were used for phylogenetic analysis of AI hemagglutinin genes and for serologic testing using antisera produced with year-specific AI virus isolates. RESULTS: Phylogenetic analysis revealed significant divergence between early LPAI H5N2 viruses (1994 - 1998) and more recent virus field isolates (2002 - 2008). Results of the HI test were markedly influenced by the selection of the AI H5N2 virus (year of isolation) used as reference antigen for the assay. These analyses indicate that LPAI H5N2 viruses in Mexico are constantly undergoing genetic drift and that serosurveillance of AI viruses is significantly influenced by the antigen or antisera used for the HI test. CONCLUSIONS: Reference viral antigens and/or antisera need to be replaced constantly during surveillance of AI viruses to keep pace with the AI antigenic drift. This strategy should improve the estimation of antigenic differences between circulating AI viruses and the selection of suitable vaccine strains.
Assuntos
Antígenos Virais/genética , Deriva Genética , Vírus da Influenza A Subtipo H5N2/genética , Influenza Aviária/virologia , Aves Domésticas , Animais , Testes de Inibição da Hemaglutinação/veterinária , Vírus da Influenza A Subtipo H5N2/isolamento & purificação , Vacinas contra Influenza/imunologia , Influenza Aviária/epidemiologia , Influenza Aviária/prevenção & controle , México/epidemiologia , Dados de Sequência Molecular , Filogenia , Estudos Soroepidemiológicos , Fatores de TempoRESUMO
Since 2006 Egypt has been facing an extensive epidemic of H5N1 highly pathogenic avian influenza (HPAI) with a huge number of outbreaks both in rural and intensively reared poultry areas. The use of efficacious vaccines in this country has been, and still remains, essential for the control and possible eradication of HPAI. The present study was performed to establish whether the administration of inactivated vaccines containing an H5 virus belonging to a different lineage to the Eurasian H5N1 HPAI viruses guarantees protection from clinical signs, provides significant immune response and is able to achieve a reduction of viral shedding in the face of a challenge with a contemporary H5N1 virus isolated in Egypt. Despite the genetic and antigenic differences between the vaccine strain (H5N2/Mexico) and the challenge strain (H5N1/Egypt), confirmed by molecular and serological (haemagglutination inhibition) tests, it was established that the immune response induced by these conventional vaccines is sufficient to prevent infection in the majority of birds challenged with a contemporary H5N1 Egyptian strain. The data reported in this study also indicate that there may be a low degree of correlation between haemagglutination inhibition titres, clinical protection and reduction of shedding.
Assuntos
Virus da Influenza A Subtipo H5N1/imunologia , Vírus da Influenza A Subtipo H5N2/imunologia , Influenza Aviária/epidemiologia , Influenza Aviária/imunologia , Animais , Formação de Anticorpos , Galinhas/imunologia , Galinhas/virologia , Egito/epidemiologia , Virus da Influenza A Subtipo H5N1/genética , Virus da Influenza A Subtipo H5N1/isolamento & purificação , Vírus da Influenza A Subtipo H5N2/genética , Vírus da Influenza A Subtipo H5N2/isolamento & purificação , Aves Domésticas/imunologia , Aves Domésticas/virologia , Reação em Cadeia da Polimerase Via Transcriptase Reversa , Organismos Livres de Patógenos Específicos , Vacinas de Produtos Inativados/administração & dosagem , Vacinas de Produtos Inativados/uso terapêutico , Vacinas Virais/administração & dosagem , Vacinas Virais/uso terapêutico , Eliminação de Partículas Virais/imunologiaRESUMO
Antigenic drift of avian influenza viruses (AIVs) has been observed in chickens after extended vaccination program, similar to those observed with human influenza viruses. To evaluate the evolutionary properties of endemic AIV under high vaccination pressure (around 2 billion doses used in the last 12 years), we performed a pilot phylogenic analysis of the hemagglutinin (HA) gene of AIVs isolated from 1994 to 2006. This study demonstrates that Mexican low pathogenicity (LP) H5N2-AIVs are constantly undergoing genetic drifts. Recent AIV isolates (2002-2006) show significant molecular drifts when compared with the H5N2 vaccine-strain or other field isolates (1994-2000). This study also demonstrates that molecular drifts in the HA gene lineages follow a yearly trend, suggesting gradually cumulative sequence mutations. These findings might explain the increasing incidence of LP H5N2 AIV isolated from commercial avian farms. These findings support recent concerns about the challenge of AIV antigenic drift and influenza epidemics.