*4.1. Viruses*

Two different WNV isolates from the Mediterranean basin were used in this study: Morocco/2003 (strain 04.05, GenBank acc. n◦: AY701413) [20] and Spain/2007 (strain GE-1b/B, GenBank acc. n◦: FJ766331) [21]. Details on the preparation of the inocula are given in Sotelo et al. [17].

### *4.2. Experimental Infection*

The partridges were obtained, maintained, handled, and inoculated as described in Sotelo et al. [17]. Briefly, two groups of 7-week-old red-legged partridges were subcutaneously inoculated in the cervical region with 10<sup>4</sup> PFU/individual of either WNV Morocco/2003 or Spain/2007 diluted in up to 0.1 mL Dulbecco's Minimum Essential Medium (DMEM) (supplemented with 2 mM L-glutamine, 100 U/mL penicillin, and 100 μg/mL streptomycin). For the specific purpose of the present study, we performed euthanasia by intravenous injection of embutramide (T61®, Intervet–Schering-Plough, Madrid, Spain) on two birds of each group at days 3 and 6 post-inoculation (dpi), and of two birds infected with Spain/2007 and one infected with Morocco/2003 at 14 dpi.
