High death rates are most frequently observed among passeriform birds, of which the family Corvidae comprises the most highly susceptible species to WNV ( 4). The virus subsequently spread rapidly across the continent, becoming the leading cause of arboviral encephalitis in humans and horses ( 2), and it was associated with deaths among at least 326 bird species ( 3). In 1999, WNV emerged in North America, where it was first detected in New York, New York. WNV has an extensive geographic range that includes Europe, Africa, the Middle East, southern Asia, and Australia ( 1). West Nile virus (WNV), a flavivirus (family Flaviviridae) transmitted by mosquitoes, uses birds as its primary vertebrate reservoir host. These results suggest that carrion crows are highly susceptible to WNV and may potentially be useful as part of dead bird surveillance for early warning of WNV activity in Europe. Infection with all strains, except WNV FIN, resulted in high rates of death and high-level viremia in both bird species and virus dissemination to several organs. We also inoculated American crows with a selection of these strains to examine the strains’ virulence in a highly susceptible bird species. To examine the susceptibility of the western European counterpart of American crows, we inoculated carrion crows ( Corvus corone) with WNV strains isolated in Greece (Gr-10), Italy (FIN and Ita09), and Hungary (578/10) and with the highly virulent North American genotype strain (NY99). In contrast, a low incidence of bird deaths has been observed during WNV epidemic activity in Europe. West Nile virus (WNV) outbreaks in North America have been characterized by substantial die-offs of American crows ( Corvus brachyrhynchos).
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