Pathogenicity of West Nile Virus in Chickens

Abstract

In the fall of 1999, West Nile virus (WNV) was isolated for the first time in the Western Hemisphere during an outbreak of neurologic disease in humans, horses, and wild and zoo birds in the northeastern United States. Chickens are a potential reservoir for WNV, and little is known about the pathogenicity of WNV in domestic chickens. Seven-week-old chickens derived from a specific-pathogen-free flock were inoculated subcutaneously with 1.8 x 10(3) 50% tissue culture infectious dose of a crow isolate of WNV in order to observe clinical signs and evaluate the viremic phase, gross and microscopic lesions, contact transmission, and immunologic response. There were no observable clinical signs in the WNV-inoculated chickens during the 21-day observation period. However, histopathologic examination of tissues revealed myocardial necrosis, nephritis, and pneumonitis at 5 and 10 days postinoculation (DPI); moderate to severe nonsuppurative encephalitis also was observed in brain tissue from one of four inoculated birds examined at 21 DPI. WNV was recovered from blood plasma for up to 8 DPI. Virus titers as high as 10(5)/ml in plasma were observed at 4 DPI. Fecal shedding of virus was detected in cloacal swabs on 4 and 5 DPI only. The WNV also was isolated from myocardium, spleen, kidney, lung, and intestine collected from chickens euthanatized at 3, 5, and 10 DPI. No virus was isolated from inoculated chickens after 10 DPI. Antibodies specific to WNV were detected in inoculated chickens as early as 5 DPI by the plaque reduction neutralization test and 7 DPI by the indirect fluorescent antibody test. Chickens placed in contact with inoculated chickens at 1 DPI lacked WNV-specific antibodies, and no WNV was isolated from their blood plasma or cloacal swabs throughout the 21 days of the experiment.

West Nile Virus Detection in the Organs of Naturally Infected Blue Jays (Cyanocitta Cristata)

“…However, histopathologic lesions of encephalitis were not observed, and renal lesions were uncommon in the blue jays in this study, similar to reported findings in blue jays, crows, chickens, and turkeys (Senne et al, 2000;Swayne et al, 2001;Weingartl et al, 2004).…”

“…Gross hemorrhage of the brain, splenomegaly, meningoencephalitis, and myocarditis were the most prominent lesions noted in birds found dead at the beginning of the WNV epidemic (Steele et al, 2000). Subsequent studies noted similar lesions in experimentally infected blue jays, crows, chickens, and turkeys, as well as naturally infected owls (Senne et al, 2000;Swayne et al, 2000;Fitzgerald et al, 2003;Weingartl et al, 2004;Wü nschmann et al, 2004). No pathognomonic lesions for WNV have been described, however, and lesions between species are not consistent.…”

EXPERIMENTAL SUSCEPTIBILITY OF WOOD DUCKS (AIX SPONSA) FOR WEST NILE VIRUS

“…West Nile virusneutralizing antibodies have been reported as early as 5-7 d pi in experimentally challenged chickens (Senne et al 2000;Langevin et al 2001). Endpoint PRNT titers at 14 d in the present study are comparable to those developing in chickens at 14 d (Senne et al 2000;Langevin et al 2001).…”

Detection and Characterization of Naturally Acquired West Nile Virus Infection in a Female Wild Turkey

“…However, lesions in brain or other tissues were not observed in domestic turkeys inoculated with WNV. 15,16 The pathology of WNV and the viral tissue tropism in the turkey of this report were similar to what was found in many zoologic birds and wild birds, but not in experimentally infected domestic turkeys. 13 The levels of viremia in chickens and geese infected with WNV was sufficiently high to contribute to the transmission cycle, but the viral concentrations in domestic turkeys inoculated with WNV was insufficient to infect mosquitoes.…”