Implementation of a sampling strategy to detect West Nile virus in oral and cloacal samples in live song birds

In 1999, West Nile virus (WNV) first appeared in the United States and has subsequently infected more than a million people and untold numbers of wildlife. Though primarily an avian virus, WNV can also infect humans and horses. The current status of WNV and its effects on wildlife in Pennsylvania (PA) is sparsely monitored through sporadic testing of dead birds. In order to acquire a more comprehensive understanding of the status of WNV in wild birds, a study was designed and implemented to sample populations of migratory and local birds at Powdermill Nature Reserve near Rector, PA. Resident and migratory bird species totaling 276 individuals were sampled cloacally and orally to compare the effectiveness of sampling methods. The presence of WNV was tested for using RT-PCR. Two positive samples were found, one from a migrating Tennessee warbler and another from an American robin. The low infection rates indicate that WNV may not be a critical conservation concern in the Westmoreland County region of PA. There was also agreement between oral and cloacal swabs, which provides support for both methods. This study describes a surveillance method that is easily incorporated into any banding operation and which determines the risks of WNV to various bird populations.