A Retrospective Study on the Seroprevalence of West Nile Virus Among Donkeys and Mules in Bulgaria

West Nile virus (WNV) infection, caused by a flavivirus, emerged in Europe and America in the past two decades. The etiological agent causes asymptomatic to life-threatening infection in humans and in some animal species. The objective of this study was to evaluate the seroprevalence of WNV among donkeys and mules in Bulgaria.