Agricultural area increases the infection risk of free ranging birds to
St. Louis encephalitis and West Nile viruses (Flavivirus)
Abstract
Anthropogenic changes affect biological communities of host and vectors
driving arbovirus activity. In general, urban and agricultural
ecosystems harbor less avian and mosquito diversity than native
ecosystems and are dominated by few species. Human activities have led
to the emergence / re-emergence of different infectious pathogens
particularly arboviruses representing a threat to both public health and
biodiversity. Saint Louis encephalitis (SLEV) and West Nile viruses
(WNV) are transmitted by Culex spp. mosquitoes as main vectors and
several bird species as hosts. With the aim to study the exposure of
free-ranging bird communities to SLEV and WNV in Pampean agroecosystems
as well as to evaluate the environmental/ biological factors potentially
associated we collected and bleed free ranging birds in 12 sites. Serum
samples were analyzed by Plaque Reduction Neutralization Test (PRNT) for
both viruses. Generalized Linear Mixed Models (GLMM) were performed to
analyze the association between environmental / biological variables
from each sampled site and avian exposition. A total of 1019 birds were
sampled during 2017 - 2019. Overall, we found SLEV NTAb in 60 out of
1019 samples (5.8%) while WNV seroprevalence was 2.1% (21/1019). SLEV
and WNV seroprevalence were different among the sampled sites.
Agricultural area was positively associated with the SLEV-WNV infection
risk for an avian host. Forested area also had a strong association but
in a negative way. Our results suggest that open agricultural area
increase the infection risk of free ranging birds to SLEV and WNV while
forested area diminishes the infection risk maybe through a dilution
effect of vector and host communities.