Wetlands in Argentinaas hubs for exchange and emigration of bird-borne arboviruses

Abstract Arthropod-borne viruses (arboviruses) are emerging at an unprecedented rate due to cultural, biological, environmental, climatic, and social changes. Historically, considerable attention has been paid to the role of human-mediated transportation in the dispersal and emergence of arboviruses amplified by birds. However, few studies have focused on the role of migratory birds as disseminators of these viruses. In most migratory bird species, seasonal migration consists of a series of consecutive stops where birds rest and feed en route to their final destination. Wetlands, due to their high stability and productivity, offer excellent habitat for resident birds as well as stopover and hibernation sites for migratory birds. Consequently, both groups of birds can reach exceptionally high densities in wetlands. Wetlands are also known to harbor a high density and abundance of arbovirus vectors, particularly mosquitoes. St. Louis encephalitis virus (SLEV) and West Nile virus (WNV) are two mosquito-borne flaviviruses amplified by birds. WNV was introduced to the Americas in 1999 and rapidly spread throughout North, Central, and South America. On the other hand, SLEV is endemic to the Americas. In our country, its role as a human pathogen emerged in 2002. Possibly due to competition with WNV, SLEV activity decreased in most parts of the United States. However, in 2015, SLEV re-emerged in the western United States. Phylogenetic analyses confirmed that the (re)emergent SLEV strain belonged to genotype III, related to a strain isolated in Córdoba, Argentina Representing the first detection of this genotype in the United States. Recently, we detected the closest common ancestor to the introduced strain in the United States in a pool of Culex maxi mosquitoes collected in May 2014 in Laguna Mar Chiquita (LMC) in the province of Córdoba, Argentina. Based on the hypothesis that wetlands represent a hub for exchange and emigration of bird-borne arboviruses, we propose to characterize the network of vector-host-virus interactions within MCL/BdRD. To the best of our knowledge, this is the first comprehensive characterization of a wetland as a hub for arbovirus exchange between resident and migratory birds in the Americas. This study will: i) identify host bloodmeals in wetland mosquitoes to elucidate the potential viral flow between resident and migratory birds, ii) analyze the previous exposure of migratory and resident birds to SLE and WN viruses using serosurveillance, to identify key hosts in transmission networks of these viruses, iii) identify mosquito species infected with SLE and WN viruses that could potentially act as vectors for these viruses, iv) describe the phylogenetic and phylogeographic relationships of viral strains circulating in the wetland with strains previously detected in the Americas region and v) evaluate the vector and host competence role of Culex mosquito species and urban bird species. While aspects of these transmission cycles have been studied, this will be the first time they have been integrated in a single, key habitat.