In strain NY99 infected birds, the median peak viral RNA titer was 108.7 RNA copies/mL of serum (range 10 1010.0 [nontransformed values]), and the median peak infectious virus titer was 107.4 TCID50/mL of serum (range 101.8 108.8); these values include 1 bird in which detectable viremia did not develop during the entire course of infection.
During the 15-day observation period, clinical signs did not develop in any of the birds; none of the birds died.
Antibodies to ABV did not develop in the sentinel bird (se1) during the investigation period; however, increasing amounts of ABV RNA were detected in swab samples from the bird beginning 76 dpi.
These bird species were considered reservoir competent for WNV, whereas species that did not develop viremia of sufficient titer to infect these mosquitoes were considered incompetent.
Mosquitoes that feed on both birds and mammals are referred to as bridge vectors for WNV because they act as a "bridge" between an infected reservoir (birds) and mammalian incidental hosts which do not develop sufficiently high viremia to support transmission to mosquitoes [ 110, 111].
Viremia does not develop in most passerine birds (3,4), which are not able to pass the virus to ticks.
In birds, the postovulatory follicle shrinks, and identifiable corpora lutea do not develop, although some granulosa cells accumulate lipids of unknown significance.
The birds do not usually develop clinical disease, but they shed a large number of virus particles in their faeces, which may cause serious disease outbreaks when introduced into poultry flocks.
