Reisen William K, Hahn D Caldwell
Center for Vectorborne Diseases and Department of Pathology, Microbiology and Immunology, School of Veterinary Medicine, University of California, Davis, California 95616, USA.
J Wildl Dis. 2007 Jul;43(3):439-49. doi: 10.7589/0090-3558-43.3.439.
The rapid geographic spread of West Nile virus (family Flaviviridae, genus Flavivirus, WNV) across the United States has stimulated interest in comparative host infection studies to delineate competent avian hosts critical for viral amplification. We compared the host competence of four taxonomically related blackbird species (Icteridae) after experimental infection with WNV and with two endemic, mosquito-borne encephalitis viruses, western equine encephalomyelitis virus (family Togaviridae, genus Alphavirus, WEEV), and St. Louis encephalitis virus (family Flaviviridae, genus Flavivirus, SLEV). We predicted differences in disease resistance among the blackbird species based on differences in life history, because they differ in geographic range and life history traits that include mating and breeding systems. Differences were observed among the response of these hosts to all three viruses. Red-winged Blackbirds were more susceptible to SLEV than Brewer's Blackbirds, whereas Brewer's Blackbirds were more susceptible to WEEV than Red-winged Blackbirds. In response to WNV infection, cowbirds showed the lowest mean viremias, cleared their infections faster, and showed lower antibody levels than concurrently infected species. Brown-headed Cowbirds also exhibited significantly lower viremia responses after infection with SLEV and WEEV as well as coinfection with WEEV and WNV than concurrently infected icterids. We concluded that cowbirds may be more resistant to infection to both native and introduced viruses because they experience heightened exposure to a variety of pathogens of parenting birds during the course of their parasitic life style.
西尼罗河病毒（黄病毒科黄病毒属，WNV）在美国的迅速地理扩散激发了人们对比较宿主感染研究的兴趣，以确定对病毒扩增至关重要的禽类宿主。我们在对四种分类学上相关的黑鹂物种（拟鹂科）进行西尼罗河病毒实验感染后，比较了它们与两种地方性蚊媒脑炎病毒（西部马脑炎病毒，披膜病毒科甲病毒属，WEEV；圣路易斯脑炎病毒，黄病毒科黄病毒属，SLEV）的宿主易感性。我们根据生活史差异预测了黑鹂物种之间的抗病性差异，因为它们在地理分布范围以及包括交配和繁殖系统在内的生活史特征方面存在差异。观察到这些宿主对所有三种病毒的反应存在差异。红翅黑鹂比棕头歌雀更容易感染圣路易斯脑炎病毒，而棕头歌雀比红翅黑鹂更容易感染西部马脑炎病毒。在感染西尼罗河病毒后，褐头牛鹂的平均病毒血症最低，清除感染更快，并且与同时感染的物种相比，抗体水平更低。在感染圣路易斯脑炎病毒和西部马脑炎病毒以及同时感染西部马脑炎病毒和西尼罗河病毒后，褐头牛鹂的病毒血症反应也明显低于同时感染的拟鹂科鸟类。我们得出结论，褐头牛鹂可能对本地和外来病毒的感染更具抵抗力，因为在其寄生生活方式中，它们接触育雏鸟类各种病原体的机会增加。
