Pathogenesis of Two Western Mediterranean West Nile Virus Lineage 1 Isolates in Experimentally Infected Red-Legged Partridges (Alectoris rufa)

Abstract

West Nile virus (WNV) is the most widespread flavivirus in the world with a wide vertebrate host range. Its geographic expansion and activity continue to increase with important human and equine outbreaks and local bird mortality. In a previous experiment, we demonstrated the susceptibility of 7-week-old red-legged partridges (Alectoris rufa) to Mediterranean WNV isolates Morocco/2003 and Spain/2007, which varied in virulence for this gallinaceous species. Here we study the pathogenesis of the infection with these two strains to explain the different course of infection and mortality. Day six post-inoculation was critical in the course of infection, with the highest viral load in tissues, the most widespread virus antigen, and more severe lesions. The most affected organs were the heart, liver, and spleen. Comparing infections with Morocco/2003 and Spain/2007, differences were observed in the viral load, virus antigen distribution, and lesion nature and severity. A more acute and marked inflammatory reaction (characterized by participation of microglia and CD3+ T cells) as well as neuronal necrosis in the brain were observed in partridges infected with Morocco/2003 as compared to those infected with Spain/2007. This suggests a higher neurovirulence of Morocco/2003, probably related to one or more specific molecular determinants of virulence different from Spain/2007.

Pathogenesis of West Nile Virus Lineage 2 in Domestic Geese after Experimental Infection

“…The feather pulps were frequently infected in 9/15 geese up to 14 dpi, as detected by RT-qPCR, containing up to 10 6.1 TCID 50 /mL (G 8, 3 dpi), as proven by virus titration (Table S6). Thus, the virus was detectable in the feather pulps for a longer duration than in the blood in both our study and in red-legged partridges (Alectoris rufa) infected with a WNV lineage 1 strain [42]. Therefore, our results not only support direct horizontal transmission cycles via pulp by feather pecking but also indicate an alternative method for collecting and analyzing feather pulps for the monitoring of WNV in live/succumbed (wild/zoo) birds.…”

“…This is in accordance with the viral load seen in RT-qPCR (Figure 6, Table S5), showing positive IHC staining only with CT values below 20. Furthermore, in other studies, IHC was positive only at high viral loads detected by RT-qPCR and at early time points pi because of the lower sensitivity compared to RT-qPCR [42,58,59]. This lower sensitivity could be due to the fact that the antibody of the IHC detects a different target than the RT-qPCR or that only many small amounts of antigen are present in the tissue.…”

Experimental infections in red-legged partridges reveal differences in host competence between West Nile and Usutu virus strains from Southern Spain

“…Notably, it was found to reach viremic levels high enough to infect mosquitoes (i.e., it is a competent host). Furthermore, it is useful to discriminate between WNV strains in terms of pathogenicity ( Sotelo et al., 2011 ; Pérez-Ramírez et al., 2018 ; Gamino et al., 2021 ). However, the susceptibility of this wild bird species to USUV infection and disease, as well as its competence for virus transmission and overall epidemiological role, is still unclear.…”

West Nile Virus Infection

“…In relation to WNV pathogenesis Gamino et al [ 7 ] delved into the pathogenesis of WNV in birds. In a previous study the authors demonstrated the susceptibility of red-legged partridge ( Alectoris rufa ) to two Mediterranean WNV strains from Morocco and Spain via experimental infection, showing higher mortality and morbidity in the birds infected with the Moroccan isolate.…”