West Nile Virus Seroprevalence in Horses from Romania: First Step in the Infection Risk Assessment

West Nile virus (WNV) infections are known to be endemic in some areas of Romania. After the last epidemics registered in 2010 in the country, it is considered that WNV has changed its patterns of evolution. The surveillance of West Nile virus includes surveillance of host species and mosquitoes vectors in order to assess the risk of WNV infection in human population. In this paper we describe the preliminary investigations made for the establishment of mosquitoes collection sites consisting in a seroepidemiological study for the detection of WNV specific antibodies made in three counties from the eastern Romania. Horse blood samples were collected from Buzau, Braila and Tulcea Counties. From these, 60 samples were chosen randomly (at least 5 from each sampling area) and tested using a competitive ELISA. The results showed that in Tulcea and Braila Counties WNV is enzootic. In Tulcea, high values of seroconversion were registered not only in Danube Delta (eastern part of the County), but also in the central and southern area of the county. As for Buzau County, the tested sera were negative for specific anti WNV antibodies. In Braila and Tulcea Counties, the high rates of seroprevalence in certain areas permitted us to establish collecting sites for mosquitoes. In Buzau County West Nile virus specific antibodies were not detected until now. The collection of mosquitoes and further detection of WNV will gave us the possibility to characterize WNV circulating strains in Romania and to determine the risk areas for human infection.