Economic factors influencing zoonotic disease dynamics: demand for poultry meat and seasonal transmission of avian influenza in Vietnam

Alexis Delabouglise,Marc Choisy,Marisa Peyre,Nicolas Antoine-Moussiaux,Guillaume Fournié,Ton D Vu,Thang D Phan,Dirk U Pfeiffer

doi:10.1038/s41598-017-06244-6

Abstract

While climate is often presented as a key factor influencing the seasonality of diseases, the importance of anthropogenic factors is less commonly evaluated. Using a combination of methods – wavelet analysis, economic analysis, statistical and disease transmission modelling – we aimed to explore the influence of climatic and economic factors on the seasonality of H5N1 Highly Pathogenic Avian Influenza in the domestic poultry population of Vietnam. We found that while climatic variables are associated with seasonal variation in the incidence of avian influenza outbreaks in the North of the country, this is not the case in the Centre and the South. In contrast, temporal patterns of H5N1 incidence are similar across these 3 regions: periods of high H5N1 incidence coincide with Lunar New Year festival, occurring in January-February, in the 3 climatic regions for 5 out of the 8 study years. Yet, daily poultry meat consumption drastically increases during Lunar New Year festival throughout the country. To meet this rise in demand, poultry production and trade are expected to peak around the festival period, promoting viral spread, which we demonstrated using a stochastic disease transmission model. This study illustrates the way in which economic factors may influence the dynamics of livestock pathogens.

Highlights

While climate is often presented as a key factor influencing the seasonality of diseases, the importance of anthropogenic factors is less commonly evaluated
In Thailand and Vietnam, the farming of free-grazing ducks in association with rice cultivation was shown to play a key role in the persistence and spread of the virus[14,15,16] while a study in Bangladesh pointed that the presence of migratory birds’ staging areas, rivers and road used for trade and live bird markets were significant risk factors of H5N1 outbreaks[17]
In order to understand the influence of climate and poultry meat consumption on the temporal dynamics of avian influenza (AI) in Vietnam, we applied different statistical and mathematical analysis methods to the data

Summary

Introduction

While climate is often presented as a key factor influencing the seasonality of diseases, the importance of anthropogenic factors is less commonly evaluated. The temporal dynamics of zoonotic influenza viruses, which are transmitted from domestic animals to humans, have been comparatively less studied than those between humans, partly because their emergence as a public health concern is relatively recent. Examples of such viruses are H5N1 and H7N9 subtypes of influenza A, circulating in the domestic poultry populations of several countries in East, South and Southeast Asia, West Africa and Egypt[5, 6]. A farm level case-control study has demonstrated that poultry farms with a high frequency of bird introduction or being located in the neighbourhood of poultry traders are at higher risk of AI infection[18] while the potential role of live bird trade in AI propagation was pointed out[19]

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