Antibodies to West Nile virus and related flaviviruses in wild boar, red foxes and other mesomammals from Spain.

Red foxes (Vulpes vulpes), wild boar (Sus scrofa) and Iberian pigs (Sus scrofa domestica) that are raised extensively outdoors, as well as other wild mesomammals from south central Spain and wild boar from Doñana National Park (DNP), were tested for antibodies against related flaviviruses by ELISA and for antibodies against WNV by VNT. Mean flavivirus seroprevalence according to ELISA was 20.4 ± 7.8% (21 out of 103) in red foxes, 12.6 ± 2.8% (69 out of 545) in wild boars, and 3.3±2.7% (6 out of 177) in Iberian pigs. A stone marten (Martes foina) also tested positive. Flavivirus seroprevalence in wild boar was significantly higher in DNP, and increased with age. Haemolysis of the serum samples limited interpretation of VNT to 28 samples, confirming WNV seroprevalence in one red fox, four Iberian pigs and nine wild boars. ELISA positive, microVNT negative samples suggest presence of non-neutralizing antibodies against WNV or antibodies to other antigenically related flaviviruses. Despite the importance of wetlands for flavivirus maintenance and amplification, WNV/flavivirus seroprevalence in wild boar and red foxes was not associated to wetland habitats. This is the first report of exposure of red foxes to WNV. With view to use of the tested species as sentinels for flavivirus activity, limited exposure of Iberian pigs that would be available for regular sampling, low numbers of foxes collected and concentration of wild boar harvest in the winter season are major drawbacks.