Unusually High Mortality in Waterfowl Caused by Highly Pathogenic Avian Influenza A(H5N1) in Bangladesh

Najmul Haider, K. Sturm-Ramirez, S. U. Khan, M. Z. Rahman, S. Sarkar, M. K. Poh, H. L. Shivaprasad, M. A. Kalam, S. K. Paul, P. C. Karmakar, A. Balish, A. Chakraborty, A. A. Mamun, A. B. Mikolon, C. T. Davis, M. Rahman, R. O. Donis, J. D. Heffelfinger, S. P. Luby, N. Zeidner

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    Abstract

    Mortality in ducks and geese caused by highly pathogenic avian influenza A(H5N1) infection had not been previously identified in Bangladesh. In June-July 2011, we investigated mortality in ducks, geese and chickens with suspected H5N1 infection in a north-eastern district of the country to identify the aetiologic agent and extent of the outbreak and identify possible associated human infections. We surveyed households and farms with affected poultry flocks in six villages in Netrokona district and collected cloacal and oropharyngeal swabs from sick birds and tissue samples from dead poultry. We conducted a survey in three of these villages to identify suspected human influenza-like illness cases and collected nasopharyngeal and throat swabs. We tested all swabs by real-time RT-PCR, sequenced cultured viruses, and examined tissue samples by histopathology and immunohistochemistry to detect and characterize influenza virus infection. In the six villages, among the 240 surveyed households and 11 small-scale farms, 61% (1789/2930) of chickens, 47% (4816/10 184) of ducks and 73% (358/493) of geese died within 14 days preceding the investigation. Of 70 sick poultry swabbed, 80% (56/70) had detectable RNA for influenza A/H5, including 89% (49/55) of ducks, 40% (2/5) of geese and 50% (5/10) of chickens. We isolated virus from six of 25 samples; sequence analysis of the hemagglutinin and neuraminidase gene of these six isolates indicated clade 2.3.2.1a of H5N1 virus. Histopathological changes and immunohistochemistry staining of avian influenza viral antigens were recognized in the brain, pancreas and intestines of ducks and chickens. We identified ten human cases showing signs compatible with influenza-like illness; four were positive for influenza A/H3; however, none were positive for influenza A/H5. The recently introduced H5N1 clade 2.3.2.1a virus caused unusually high mortality in ducks and geese. Heightened surveillance in poultry is warranted to guide appropriate diagnostic testing and detect novel influenza strains.
    Original languageEnglish
    JournalTransboundary and Emerging Diseases
    Volume64
    Issue number1
    Pages (from-to)144-156
    Number of pages13
    ISSN1865-1674
    DOIs
    Publication statusPublished - 2017

    Keywords

    • Bangladesh
    • H5N1 subtype
    • Clade 2.3.2.1a
    • Duck
    • Goose
    • Histopathology
    • Immunohistochemistry
    • Influenza A virus
    • Outbreaks

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