Ecological Determinants of Highly Pathogenic Avian Influenza (H5N1) Outbreaks in Bangladesh

Abstract

BackgroundThe 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 FindingsAn 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/SignificanceThe 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.

Combining phylogeography and spatial epidemiology to uncover predictors of H5N1 influenza A virus diffusion

“…This discrepancy could be explained by the fact that Egypt’s population density is approximately 24-fold that of Canada’s [37,38] so human-to-human transmission is far more likely. Poultry density and household density were also found to be among ecological determinants of H5N1 spread in Bangladesh [39]. Since our model analyzed the same virus in a country where live bird markets are also prevalent [40] these conclusions strongly suggest that both avian and human population sizes are reliable indicators of H5N1 diffusion.…”

Global mapping of highly pathogenic avian influenza H5N1 and H5Nx clade 2.3.4.4 viruses with spatial cross-validation

“…The majority of these have been country-level studies in Thailand (Gilbert et al, 2006), Viet Nam (Minh et al, 2009), China (Martin et al, 2011), Bangladesh (Ahmed et al, 2012), Indonesia (Yupiana et al, 2010) and India (Dhingra et al, 2014). Several studies have also been conducted at regional (Adhikari D, 2009; Gilbert et al, 2008; Williams and Peterson, 2009) and continental levels (Hogerwerf et al, 2010; Peterson and Williams, 2008).…”

Detection of Specific type-A Antigen and Specific Antibody against Avian Influenza virus in Native Duck at Netrokona district of Bangladesh

“…The total poultry population, both backyard and commercial, accounts to approximately 210 million, producing 5400 million pieces of eggs annually and nearly 15% of total animal protein (Asifuddin, 2013). In fact, Bangladesh, with duck stocks of 38.1 million, has the third largest duck population in the world (Ahmed et al, 2012). Ducks are generally kept along with backyard chickens and they are intermingling with chickens during forage.…”