tetano
Editor, Senior Moderator
Citation: Ahmed SSU, Ersb?ll AK, Biswas PK, Christensen JP, Hannan ASMA, et al. (2012) Ecological Determinants of Highly Pathogenic Avian Influenza (H5N1) Outbreaks in Bangladesh. PLoS ONE 7(3): e33938. doi:10.1371/journal.pone.0033938
Syed S. U. Ahmed1,2*, Annette K. Ersb?ll3, Paritosh K. Biswas4, Jens P. Christensen5, Abu S. M. A. Hannan6, Nils Toft1
1 Department of Large Animal Sciences, Faculty of Life Sciences, University of Copenhagen, Frederiksberg, Copenhagen, Denmark, 2 Department of Medicine and Surgery, Faculty of Veterinary Medicine, Chittagong Veterinary and Animal Sciences University, Chittagong, Bangladesh, 3 National Institute of Public Health, University of Southern Denmark, Copenhagen, Denmark, 4 Department of Microbiology, Faculty of Veterinary Medicine, Chittagong Veterinary and Animal Sciences University, Chittagong, Bangladesh, 5 Department of Veterinary Disease Biology, Faculty of Life Sciences, University of Copenhagen, Frederiksberg, Copenhagen, Denmark, 6 Epidemiology Unit, Department of Livestock Services, Dhaka, Bangladesh
Abstract Top
Background
The agro-ecology and poultry husbandry of the south Asian and south-east Asian countries share common features, however, with noticeable differences. Hence, the ecological determinants associated with risk of highly pathogenic avian influenza (HPAI-H5N1) outbreaks are expected to differ between Bangladesh and e.g., Thailand and Vietnam. The primary aim of the current study was to establish ecological determinants associated with the risk of HPAI-H5N1 outbreaks at subdistrict level in Bangladesh. The secondary aim was to explore the performance of two different statistical modeling approaches for unmeasured spatially correlated variation.
Methodology/Principal Findings
An ecological study at subdistrict level in Bangladesh was performed with 138 subdistricts with HPAI-H5N1 outbreaks during 2007?2008, and 326 subdistricts with no outbreaks. The association between ecological determinants and HPAI-H5N1 outbreaks was examined using a generalized linear mixed model. Spatial clustering of the ecological data was modeled using 1) an intrinsic conditional autoregressive (ICAR) model at subdistrict level considering their first order neighbors, and 2) a multilevel (ML) model with subdistricts nested within districts. Ecological determinants significantly associated with risk of HPAI-H5N1 outbreaks at subdistrict level were migratory birds' staging areas, river network, household density, literacy rate, poultry density, live bird markets, and highway network. Predictive risk maps were derived based on the resulting models. The resulting models indicate that the ML model absorbed some of the covariate effect of the ICAR model because of the neighbor structure implied in the two different models.
Conclusions/Significance
The study identified a new set of ecological determinants related to river networks, migratory birds' staging areas and literacy rate in addition to already known risk factors, and clarified that the generalized concept of free grazing duck and duck-rice cultivation interacted ecology are not significant determinants for Bangladesh. These findings will refine current understanding of the HPAI-H5N1 epidemiology in Bangladesh.
http://www.plosone.org/article/info...7;jsessionid=7651E62076EA5288C2DEE16409F4547C
Syed S. U. Ahmed1,2*, Annette K. Ersb?ll3, Paritosh K. Biswas4, Jens P. Christensen5, Abu S. M. A. Hannan6, Nils Toft1
1 Department of Large Animal Sciences, Faculty of Life Sciences, University of Copenhagen, Frederiksberg, Copenhagen, Denmark, 2 Department of Medicine and Surgery, Faculty of Veterinary Medicine, Chittagong Veterinary and Animal Sciences University, Chittagong, Bangladesh, 3 National Institute of Public Health, University of Southern Denmark, Copenhagen, Denmark, 4 Department of Microbiology, Faculty of Veterinary Medicine, Chittagong Veterinary and Animal Sciences University, Chittagong, Bangladesh, 5 Department of Veterinary Disease Biology, Faculty of Life Sciences, University of Copenhagen, Frederiksberg, Copenhagen, Denmark, 6 Epidemiology Unit, Department of Livestock Services, Dhaka, Bangladesh
Abstract Top
Background
The agro-ecology and poultry husbandry of the south Asian and south-east Asian countries share common features, however, with noticeable differences. Hence, the ecological determinants associated with risk of highly pathogenic avian influenza (HPAI-H5N1) outbreaks are expected to differ between Bangladesh and e.g., Thailand and Vietnam. The primary aim of the current study was to establish ecological determinants associated with the risk of HPAI-H5N1 outbreaks at subdistrict level in Bangladesh. The secondary aim was to explore the performance of two different statistical modeling approaches for unmeasured spatially correlated variation.
Methodology/Principal Findings
An ecological study at subdistrict level in Bangladesh was performed with 138 subdistricts with HPAI-H5N1 outbreaks during 2007?2008, and 326 subdistricts with no outbreaks. The association between ecological determinants and HPAI-H5N1 outbreaks was examined using a generalized linear mixed model. Spatial clustering of the ecological data was modeled using 1) an intrinsic conditional autoregressive (ICAR) model at subdistrict level considering their first order neighbors, and 2) a multilevel (ML) model with subdistricts nested within districts. Ecological determinants significantly associated with risk of HPAI-H5N1 outbreaks at subdistrict level were migratory birds' staging areas, river network, household density, literacy rate, poultry density, live bird markets, and highway network. Predictive risk maps were derived based on the resulting models. The resulting models indicate that the ML model absorbed some of the covariate effect of the ICAR model because of the neighbor structure implied in the two different models.
Conclusions/Significance
The study identified a new set of ecological determinants related to river networks, migratory birds' staging areas and literacy rate in addition to already known risk factors, and clarified that the generalized concept of free grazing duck and duck-rice cultivation interacted ecology are not significant determinants for Bangladesh. These findings will refine current understanding of the HPAI-H5N1 epidemiology in Bangladesh.
http://www.plosone.org/article/info...7;jsessionid=7651E62076EA5288C2DEE16409F4547C