H7N9 and H5N1 avian influenza suitability models for China: accounting for new poultry and live-poultry markets distribution data

Jean Artois,Madhur S Dhingra,Shengjie Lai,Xiangming Xiao,Luzhao Feng,Catherine Linard,Marius Gilbert,Timothy P Robinson,Hui Jiang,Xiangping Li,Hongjie Yu,Hang Zhou,Gaëlle Nicolas

doi:10.1007/s00477-016-1362-z

Abstract

In the last two decades, two important avian influenza viruses infecting humans emerged in China, the highly pathogenic avian influenza (HPAI) H5N1 virus in the late nineties, and the low pathogenic avian influenza (LPAI) H7N9 virus in 2013. China is home to the largest population of chickens (4.83 billion) and ducks (0.694 billion), representing, respectively 23.1 and 58.6% of the 2013 world stock, with a significant part of poultry sold through live-poultry markets potentially contributing to the spread of avian influenza viruses. Previous models have looked at factors associated with HPAI H5N1 in poultry and LPAI H7N9 in markets. However, these have not been studied and compared with a consistent set of predictor variables. Significant progress was recently made in the collection of poultry census and live-poultry market data, which are key potential factors in the distribution of both diseases. Here we compiled and reprocessed a new set of poultry census data and used these to analyse HPAI H5N1 and LPAI H7N9 distributions with boosted regression trees models. We found a limited impact of the improved poultry layers compared to models based on previous poultry census data, and a positive and previously unreported association between HPAI H5N1 outbreaks and the density of live-poultry markets. In addition, the models fitted for the HPAI H5N1 and LPAI H7N9 viruses predict a high risk of disease presence for the area around Shanghai and Hong Kong. The main difference in prediction between the two viruses concerned the suitability of HPAI H5N1 in north-China around the Yellow sea (outlined with Tianjin, Beijing, and Shenyang city) where LPAI H7N9 has not spread intensely.

Highlights

In high-income countries, most of the intensification of poultry production took place in the second half of the 20th century and are not changing much anymore (FAO 2009)
We found a limited impact of the improved poultry layers compared to models based on previous poultry census data, and a positive and previously unreported association between highly pathogenic avian influenza (HPAI) H5N1 outbreaks and the density of live-poultry markets
For HPAI H5N1 outbreaks, this involved a predominance of anthropogenic factors with a relatively limited influence of poultry variables

Summary

Introduction

In high-income countries, most of the intensification of poultry production took place in the second half of the 20th century and are not changing much anymore (FAO 2009). Transition economies such as China or Brazil are intensifying their animal production in response to rising demands from more urbanized and wealthy human populations that are increasing their per capita consumption of poultry meat and eggs (Robinson and Pozzi 2011). Both the number and geographical distribution of poultry is changing much faster than that in high-income economies. The density of host is a key variable in any epidemiological investigations, and studies carried out in economies with a fast-changing agricultural sector need to account for those changes

Objectives

Methods

Results

Conclusion