Environmental Factors Influencing the Spread of the Highly Pathogenic Avian Influenza H5N1 Virus in wild birds in Europe

Abstract

A large number of occurrences of the highly pathogenic avian influenza (HPAI) H5N1 virus in wild birds were reported in Europe. The relationship between the occurrence pattern and environmental factors has, however, not yet been explored. This research uses logistic regression to quantify the relationships between anthropogenic or physical environmental factors and HPAI H5N1 occurrences. Our results indicate that HPAI H5N1 occurrences are highly correlated with the following: the increased normalized difference vegetation index (NDVI) in December; intermediate NDVI in March; lower elevations; increased minimum temperatures in January; and reduced precipitation in January. A predictive risk map of HPAI H5N1 occurrences in wild birds in Europe was generated on the basis of five key environmental factors. Independent validation of the risk map showed the predictive model to be of high accuracy (79%). The analysis suggests that HPAI H5N1 occurrences in wild birds are strongly influenced by the availability of food resources and are facilitated by increased temperatures and reduced precipitation. We therefore deduced that HPAI H5N1 occurrences in wild birds in Europe are probably caused by contact with other wild birds and not by contact with domestic poultry. These findings are important considerations for the global surveillance of HPAI H5N1 occurrences in wild birds.

Dilution effect in bovine tuberculosis: risk factors for regional disease occurrence in Africa

“…We tested whether these effects also influenced the probability of BTB presence at regional scale. Human population density was also used as a biotic predictor variable, as human population density could be considered as an indicator of trade activity [27], which has been proved to be positively related to BTB disease risk [19,20]. Also, since maintenance hosts can maintain the pathogen in the community without any other species and are able to play important roles in disease persistence, transmission and spread [3,6], we used the percentage of the area occupied by African buffalo and greater kudu as predictor variables to test the effects of these two maintenance host species.…”

Spatio-Temporal Occurrence Modeling of Highly Pathogenic Avian Influenza Subtype H5N1: A Case Study in the Red River Delta, Vietnam

“…Highly Pathogenic Avian Influenza (HPAI) subtype H5N1 has posed a global threat to both animal and human populations [1]. The HPAI H5N1 virus has caused unpredictable epidemics over the years.…”

“…These unpredictable changes may directly cause circulation of the avian influenza virus through water birds [9]. Although increased minimum temperature in January and decreased lower annual precipitation were respectively found to be associated with HPAI H5N1 in Europe and China [1,10], the mechanism of how space-time dynamics of these factors affected disease occurrence were not investigated. In other words, the variability of weather across space and time in relation with the occurrence of HPAI H5N1 has been overlooked.…”

A social–ecological approach to landscape epidemiology: geographic variation and avian influenza

“…They also found a positive association between AIV and duck density in the Vietnam highlands and Thailand, and with rice landscapes in Thailand and Madagascar, confirming the important role of wetlands-rice-duck ecosystems in the epidemiology of AI in SE Asia. The influence of environmental variables on AIV prevalence depends on the landscape context (Si et al 2010), and hence risk factors for one area may not be as relevant elsewhere (Williams and Peterson 2009). There is a clear need in this context for better hypotheses and theories that connect landscape structure and dynamics, in a general sense, to the prevalence of AIVs.…”