Peridomestic avian species as amplifying hosts and sentinels of West Nile virus in Georgia
Gibbs, Samantha elizabeth johnson
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Blue jays (Cyanocitta cristata) are an effective indicator species for West Nile virus (WNV). The objectives were to describe the gross and microscopic pathology associated with natural WNV infection in blue jays, and determine the most appropriate tissues to be used for virus isolation, reverse transcriptase nested polymerase chain reaction (RT-nPCR), and immunohistochemistry (IHC) techniques. Brain, heart, and lung had the highest viral titers among the tissues. WNV antigen was most often detected by IHC in heart, kidney, liver, and lung. RT-nPCR proved to be the most sensitive diagnostic test applied in this study irrespective of the tissue type. Wild caught rock pigeons (Columba livia) with WNV antibodies were monitored for 15 months to determine antibody persistence and compare results of three serologic techniques. Antibodies persisted for the entire study as detected by epitope-blocking enzyme-linked immunosorbent assay and plaque reduction neutralization test. Maternal antibodies in squabs derived from seropositive birds persisted for an average of 27 days. Avian species that are locally involved as potential amplifying hosts of WNV could serve as indicators of WNV transmission over the physiographic and land use variation present in the southeastern United States. Avian serum samples (n = 14,207) from 83 species of birds captured throughout Georgia during the summers of 2000 through 2004 were tested by plaque reduction neutralization test for antibodies to WNV. Antibodies to WNV were detected in 869 (6.1%) of the samples, increased significantly throughout the study, and were species dependent. The highest antibody prevalence rates were detected in rock pigeons (Columba livia), northern cardinals (Cardinalis cardinalis), and common ground doves (Columbina passerina). Geographic information systems (GIS) and logistic regression analyses were used to predict the distribution of WNV in the state of Georgia based on a wild bird indicator system, and to identify variables that are important in the determination of WNV distribution. Temperature, housing density, urban/suburban land use, and mountain physiographic region were important variables in predicting the distribution of WNV in the state of Georgia. The risks associated with WNV endemnicity appear to be increased in urban/suburban areas and decreased in the mountainous region of the state.