Hofmeister Erik, Porter Robert E, Franson J Christian
1 US Geological Survey, National Wildlife Health Center, 6006 Schroeder Road, Madison, Wisconsin 53711, USA.
J Wildl Dis. 2015 Apr;51(2):411-8. doi: 10.7589/2014-08-216. Epub 2015 Jan 14.
Detection of West Nile virus (WNV) has been reported in a variety of wild ducks in the US, but little is known about the pathogenesis and outcome of exposure of the disease in these species. Previous experimental studies of WNV in ducks either have challenged a small number of ducks with WNV or have tested domesticated ducks. To determine susceptibility and immune response, we challenged 7-wk-old Wood Ducks (Aix sponsa) with a 1999 American Crow (Corvus brachyrhynchos) isolate of WNV. Wood Ducks were susceptible to infection with the virus, and, although clinical signs or mortality were not observed, microscopic lesions were noted, particularly in the heart and brain. West Nile virus viremia peaked on day 2 postinfection (pi) at 10(4.54) plaque-forming units (PFU) of virus/mL serum and WNV was shed orally (between 10(2) and 10(2.9) PFU per swab) and cloacally. Specific anti-WNV antibody response was rapid, with anti-WNV IgM detected on day 3 pi followed on day 5 pi by anti-WNV IgG. Neutralizing antibodies were detected by plaque-reduction neutralization assay in one duck on day 4 pi, and in all sampled ducks on day 5. These results indicate that Wood Ducks are susceptible to WNV, but it is unlikely that significant WNV mortality events occur in Wood Ducks or that they play a significant role in transmission. However, WNV viremia was sufficient, in theory, to infect mosquitoes, and oral and cloacal shedding of the virus may increase the risk of infection to other waterbirds.
在美国，已报道在多种野鸭中检测到西尼罗河病毒（WNV），但对于这些物种感染该疾病的发病机制和结果却知之甚少。此前关于鸭感染WNV的实验研究，要么是用WNV感染少量鸭子，要么是检测家鸭。为了确定易感性和免疫反应，我们用1999年从美国乌鸦（短嘴鸦）分离出的WNV毒株感染7周龄的林鸳鸯（美洲鸳鸯）。林鸳鸯对该病毒易感，虽然未观察到临床症状或死亡情况，但发现了微观病变，尤其是在心脏和脑部。西尼罗河病毒血症在感染后第2天达到峰值，病毒滴度为10(4.54) 蚀斑形成单位（PFU）/毫升血清，WNV通过口腔（每次拭子检测到10(2)至10(2.9) PFU）和泄殖腔排出。特异性抗WNV抗体反应迅速，在感染后第3天检测到抗WNV IgM，第5天检测到抗WNV IgG。在感染后第4天，通过蚀斑减少中和试验在一只鸭子中检测到中和抗体，在第5天所有采样鸭子中均检测到。这些结果表明，林鸳鸯对WNV易感，但林鸳鸯不太可能发生大量WNV致死事件，也不太可能在传播中起重要作用。然而，理论上WNV病毒血症足以感染蚊子，病毒通过口腔和泄殖腔排出可能会增加其他水鸟的感染风险。
