Agricultural area increases the infection risk of free ranging birds to St. Louis encephalitis and West Nile viruses (Flavivirus)

Abstract

Abstract: 

Anthropogenic changes alter the structure and functionality of natural systems, impacting on their biodiversity. In Argentina, the Pampean Region is almost completely transformed into an agricultural mosaic, with impoverished biological communities dominated by a few well adapted species, which could promote the activity of arboviruses such as St. Louis encephalitis (SLEV) and West Nile (WNV). The aim of this work was to determine the exposure to SLEV and WNV of free ranging birds present in agroecosystems of La Pampa province and to evaluate the environmental and biological factors potentially associated. Birds were collected and bled in 12 sampling sites located in agroecosystems during the late summer and early autumn in 2017, 2018 and 2019. Antibodies against both viruses were detected using the Viral Neutralization Technique. The association between infection risk and environmental and biological factors was analyzed through Generalized Linear Mixed Models (GLMM), considering the sampling year as a random factor. Model selection was carried out through the Akaike Information Criterion (AIC). Overall, we found neutralizing antibodies against to SLEV in 60 out of 1019 samples (5,8%), while the WNV seroprevalence was 2,1% (21/1019). The best model that explained the variation of infection risk to SLEV in an avian host included agricultural area (wi = 0.44) with a positive effect. For WNV, the best model included the variables agricultural area + distance to the nearest body of water (wi = 0.36), having the first variable a positive and the second a negative effect. The area covered by trees had a strong negative association with the agricultural area. Our results suggest that agricultural areas increase the infection risk for an avian host by SLE and WN viruses, while tree cover would decrease the infection risk, probably through the dilution effect of host and vector communities.