Dynamics of passive immunity to West Nile virus in domestic chickens (Gallus gallus domesticus).

Birds are the principle amplifying hosts for West Nile virus (WNV), and understanding the acquisition and decay of passive immunity is important to avian surveillance and diagnostics. We characterized passive transfer of WNV-neutralizing antibody from chicken (Gallus gallus domesticus) hens to eggs and chicks and the protective efficacy and decay of maternally acquired antibody over time. We also characterized age-associated changes in magnitude of viremia and examined the possibility of vertical transmission of WNV. All egg yolks and chicks from seropositive hens were maternal antibody positive. Maternal antibodies were undetectable in most chicks by 28 days post-hatch (PH), but some chicks remained protected as late as 42 days PH. By 56 days PH, chicks from immune hens had viremia profiles similar to control chicks. There were significant age-related differences in WNV-attributed morbidity and viremia levels of unprotected chicks. Vertical transmission of WNV was not detected.