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Spread of Avian Influenza Clades in Bangladesh

Spread of Avian Influenza Clades in Bangladesh. MICHAEL WARD | Faculty of Veterinary Science. Outline. the HPAI H5N1 story in Bangladesh so far data, methods and results what does this tell us about ongoing transmission? what are the recommendations for control?. H5N1 in Bangladesh.

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Spread of Avian Influenza Clades in Bangladesh

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  1. Spread of Avian Influenza Clades in Bangladesh MICHAEL WARD | Faculty of Veterinary Science

  2. Outline • the HPAI H5N1 story in Bangladesh so far • data, methods and results • what does this tell us about ongoing transmission? • what are the recommendations for control?

  3. H5N1 in Bangladesh • Bangladesh severely affected by HPAI H5N1 • 546 outbreaks in poultry reported since 2007 • 7 confirmed human cases, one death • poultry critical to society and the economy • most numerous livestock species: 195 million • equally divided: backyard and commercial sectors • >70% of rural households rear chicken, generally free-ranging • commercial sector (semi/intensive): rapid growth in last 20 years

  4. H5N1 in Bangladesh • H5N1 confirmed March 2007 (commercial), April (backyard) • rapid disease spread throughout western parts of the country • the “first wave” (March-July 2007): 55 outbreaks • “second wave” (Sept 2007-May 2008): 232 outbreaks • first human case: 22 May 2008 • 2008/09 ‒ present: endemic infection • 546 outbreaks reported to date • mostly (86%) in commercial sector

  5. H5N1 in Bangladesh – From Epidemic to Endemic

  6. H5N1 in Bangladesh – From Epidemic to Endemic

  7. H5N1 in Bangladesh – From Epidemic to Endemic Most of the outbreaks occurred in small scale commercial farms

  8. H5N1 virus clades in Bangladesh • H5N1 viruses circulating in Bangladesh poultry • 2006: clade 2.2 likely introduced (India/Pakistan) (Dubey et al., 2012; Nagarajan et al., 2012) • 2007‒2010: clade 2.2 became endemic (Ahmed et al., 2012a) • 2010‒2011: clade 2.3.2 and 2.3.4 introduced (Islam et al., 2012; Hoque et al., 2013) • wildbirds, poultry, fomites? • introduction versus spread?

  9. How is H5N1 virus spreading in Bangladesh? 2007-2011: 50% of cases occurred in just 9 districts 80% occurred in 24 districts

  10. How is H5N1 virus spreading in Bangladesh?

  11. How is H5N1 virus spreading in Bangladesh?

  12. Spread of avian influenza clades in Bangladesh • study aim: investigate the spread of HPAI H5N1 in Bangladesh between 2010 and 2011 • data: all outbreaks reported (H5 antigen PCR ) + sample of those outbreaks in which the H5N1 virus clade was characterized via phylogenetic analysis • outbreak geolocation: database of commercial poultry operations or village location

  13. H5N1 virus clades in Bangladesh

  14. Spread of avian influenza clades in Bangladesh • descriptive statistics • mean centre, standard deviational ellipse (ArcGIS v.10) • directional statistic (Jacquez and Oden, 1994) • systematic directional spread of outbreaks during study period • relative, adjacent and following chains of infection investigated • mean direction, angular variance(ClusterSeer v. 2.5) • local indicator of autocorrelation statistic • weighted by calendar day, inverse distance squared (ArcGIS v.10)

  15. Spread of avian influenza clades in Bangladesh Outbreaks of HPAI H5N1 in flocks in Bangladesh, 1 February 2010 to 1 April 2011 n = 177

  16. Spread of avian influenza clades in Bangladesh Location of flocks in Bangladesh during 2010―2011 from which HPAI H5N1 viruses were phylogenetically characterized ●2.2 ●2.3.2.1 ▲ 2.3.4 n = 37

  17. Spread of avian influenza clades in Bangladesh Standard deviational ellipses of the distributions of locations of flocks in Bangladesh during 2010―2011 from which HPAI H5N1 viruses clade 2.2 and 2.3.2.1 were characterized

  18. Spread of avian influenza clades in Bangladesh Angular connections (ranked by date) between HPAI H5N1 poultry outbreaks in Bangladesh, 2010‒2011 Clade 2.2 Clade 2.3.2.1

  19. Spread of avian influenza clades in Bangladesh Clade 2.3.2.1 0.1860 Clade 2.2 0.2765

  20. Spread of avian influenza clades in Bangladesh Outlier locations, HPAI H5N1 poultry outbreaks in Bangladesh, 2010‒2011 Clade 2.2 Clade 2.3.2.1 early/late  ● ●  early/late ● early/late  ▲  early/early ▲

  21. What does this tell us about transmission? • clade 2.2 clade 2.3.2.1 • occurred earlier occurred later • affected more chickens affected less chickens • lower mortality higher mortality • more widely distributed central Bangladesh • outliers: central, northwest no additional outliers • northwest-southeast orientation north-south orientation • southeast―northwest spreadwest―east spread • moderate spread strong spread

  22. What does this tell us about transmission? • HPAI H5N1 infection now endemic in Bangladesh • mode of spread not well-defined • clustering of outbreaks • movement of poultry/equipment   • repeated introduction from wild bird populations   • direction test • trade in poultry   • migratory wild bird patterns  • LISA test • trade in poultry   • wild bird population 

  23. Selection bias • selection of flocks from which clades characterised: potential bias • distribution of all 177 reported outbreaks clustered • outbreaks from which clades were classified not clustered • no significant difference in the proportions of outbreaks from which clades were classified by district • selection of flocks in which clades were identified unlikely to have caused any substantial sampling bias in this study

  24. What are the recommendations for control? • HPAI H5N1 endemic in Bangladesh • reported outbreaks characterized by long-distance translocation events • challenge to disease control efforts • increased enforcement of biosecurity • stronger control of movements • surveillance and reporting

  25. Acknowledgements • MuzaffarG. Osmani, Md. RafiqulIslam • Bangladesh Agricultural University, Faculty of Veterinary Science, Department of Pathology, Mymensingh, Bangladesh • Md. Giasuddin • Bangladesh Livestock Research Institute, Savar, Bangladesh • AbulKalam • Food and Agriculture Organization, Kathmandu, Nepal

  26. Spread of Avian Influenza Clades in Bangladesh MICHAEL WARD | Faculty of Veterinary Science

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