Predicting West Nile virus seroprevalence in wild birds in Senegal.

West Nile fever epidemiology is complex, and the role of birds in the maintenance, amplification, and dissemination of the West Nile virus (WNV) remains partially unknown. In 2003, a serological study was performed in Senegal, where West Nile infection is considered endemic. The goal was to identify potential reservoirs of WNV among bird species present in the Ferlo area (northern Senegal) and the Senegal River Valley, and to screen the ecological factors possibly related to West Nile infection. Serological data were analyzed using a generalized linear model. Statistical association between ecological factors and the risk of infection were then modeled to derive a species-specific risk. A cross-validation was conducted. The overall observed prevalence rate was 5.5% (n = 422). Thirteen bird species were found positive, from which five were migrating: Lanius senator, Anthus trivialis, Hippolais opaca, Jynx torquilla, and Cercotrichas galactotes. The nesting type in resident birds was positively correlated with the risk of infection (odds ratio [OR] = 11, p = 0.0003); the gregariousness level of birds appeared as a protective factor (OR = 0.3, p = 0.01). The predicted prevalence varied between 1% and 39% for resident species and between 1% and 7% for migrating species. Results of model internal validation were satisfactory at the individual and species level. However, more field and experimental investigations are needed to confirm these preliminary results and help target the future research and surveillance in Senegal.