title: Evidence for West Nile virus spillover into the squirrel population in Atlanta, Georgia.
abstract: BACKGROUND
  In the United States, spillover of West Nile virus (WNV) into wild mammal populations has been reported since the introduction of the virus into the New World in 1999. Eastern gray squirrels (Sciurus carolinensis) exhibit a high seroprevalence for WNV in urban settings where high virus circulation and human spillover have been reported. In Atlanta, Georgia, human cases of WNV are uncommon despite high infection rates in birds and mosquitoes. In this study, we evaluated WNV exposure of eastern gray squirrels in a WNV hot spot in Atlanta.
  
  
  METHODS
  Gray squirrels were live-trapped in Grant Park, Atlanta, during July-October, 2012, and a census was conducted to estimate squirrel density in the study site. Sera from trapped animals were tested for circulating virus-by-virus isolation in cell culture and for WNV-specific antibodies by enzyme-linked immunosorbent assay and plaque reduction neutralization test. Mosquitoes were collected at the same location and tested for virus isolation.
  
  
  RESULTS
  Among the 69 collected squirrels, 25 (36.2%) tested positive for WNV antibodies, although none were viremic. Seroprevalence was lower in juveniles (18.8%) than in adults (37.5%), but this difference was not statistically significant. Gender and squirrel density had no effect on seroprevalence. Seasonality of squirrel seroprevalence and of mosquito infection were significantly associated, both peaking in August. No difference in squirrel exposure was detected across the collection sites.
  
  
  CONCLUSIONS
  We report a high degree of WNV exposure in squirrels in Grant Park that was correlated with seasonality of mosquito infection. The detection of antibodies in juveniles suggests that circulation of WNV in the surveyed population is ongoing. Eastern gray squirrels may be suitable indicators for virus amplification and for risk of human spillover on a local scale in urban settings.
authors.affiliation: 1Department of Environmental Sciences, Emory University, Atlanta, Georgia.
authors.forename: Donal
authors.initials: D
authors.lastname: Bisanzio
authors.affiliation: 1Department of Environmental Sciences, Emory University, Atlanta, Georgia.
authors.forename: Joseph R
authors.initials: JR
authors.lastname: McMillan
authors.affiliation: 2Laboratório de Dermato-Imunologia UEPA/UFPA/Marcello Candia, Marituba, Pará, Brasil.|3Universidade Federal do Pará, Campus Castanhal, Pará, Brasil.
authors.forename: Josafá Gonçalves
authors.initials: JG
authors.lastname: Barreto
authors.affiliation: 4Department of Veterinary Microbiology and Preventive Medicine, College of Veterinary Medicine, Iowa State University, Ames, Iowa.
authors.forename: Bradley J
authors.initials: BJ
authors.lastname: Blitvich
authors.affiliation: 5University of Georgia, College of Veterinary Medicine, Southeastern Cooperative Wildlife Disease Study, Athens, Georgia.
authors.forename: Daniel G
authors.initials: DG
authors.lastname: Mead
authors.affiliation: 6Fire Management Division, US Fish and Wildlife Service, Atlanta, Georgia.
authors.forename: Josh
authors.initials: J
authors.lastname: O'Connor
authors.affiliation: 1Department of Environmental Sciences, Emory University, Atlanta, Georgia.
authors.forename: Uriel
authors.initials: U
authors.lastname: Kitron
mesh_terms: D000818:Animals; D000914:Antibodies, Viral / Q000097:blood*; D001717:Birds / Q000821:virology*; D009033:Culicidae / Q000821:virology*; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D009500:Neutralization Tests / Q000662:veterinary; D012589:Sciuridae / Q000821:virology*; D016036:Seroepidemiologic Studies; D014481:United States / Q000453:epidemiology; D014901:West Nile Fever / Q000453:epidemiology / Q000662:veterinary*; D014902:West Nile virus / Q000276:immunology* / Q000302:isolation & purification; D015047:Zoonoses
chemical_list: D000914:Antibodies, Viral
keywords: Arbovirus(es); Culex; Gray squirrels; Rodents; West Nile Virus; Zoonosis