**2. Results**

### *2.1. Clinical Signs and Gross Pathology*

As described in our previous study [17], clinical signs included loss of appetite, ruffled feathers, paralysis, and lack of responsiveness. These started earlier (4 vs. 5 dpi) and were more severe in partridges infected with Morocco/2003. Macroscopic lesions were observed in all euthanized animals from 3 dpi on. The most affected organs were the heart, spleen, liver, and kidney. While the heart and kidney showed lesions from 3 dpi, the spleen and liver were not affected until 6 dpi. Main macroscopic lesions were pallor of the myocardium and hepatic, splenic, and renal parenchyma, as well as the presence of diffuse petechiae. At 14 dpi, congestion of the kidney and lung were also observed.

### *2.2. Virus Genome Detection*

All tissue samples collected from euthanized animals at 3 and 6 dpi tested positive by RRT-PCR. The lowest Ct values (i.e., highest viral loads) were reached at 6 dpi (Table 1). The viral load in tissues, estimated using Ct values, was similar in Morocco/2003- and Spain/2007-infected partridges (or slightly higher for Morocco/2003) (Table 1). At 3 and 6 dpi, the highest viral loads were found in the spleen, kidney, and heart (Table 1). High amounts of viral RNA were also detected in feather pulps collected at 6 dpi (Table 1). At 14 dpi, viral loads were low in most cases, and several tissues were negative in the Spain/2007-infected partridges (Table 1).
