Department of Fisheries and Wildlife, Michigan State University, East Lansing, MI 44824, USA.
J Med Entomol. 2011 Jul;48(4):896-903. doi: 10.1603/me10274.
Eastern equine encephalitis virus (EEEV; family Togaviridae, genus Alphavirus) epizootics are infrequent, but they can lead to high mortality in infected horses and humans. Despite the importance of EEEV to human and animal health, little is known about how the virus overwinters and reinitiates transmission each spring, particularly in temperate regions where infected adult mosquitoes are unlikely to survive through the winter. One hypothesis to explain the mechanism by which this virus persists from year to year is the spring recrudescence of latent virus in avian reservoir hosts. In this study, we tested the recrudescence hypothesis with gray catbirds (Dumatella carolinensis) captured in northern Ohio (July-August 2007). Birds were experimentally infected with EEEV on 1 October 2007. In January 2008, they were then exposed to exogenous testosterone and/or extended photoperiod to initiate reactivation of latent EEEV infection. All birds became viremic with EEEV, with mean viremia of 6.0 log10 plaque-forming units/ml serum occurring at 1 d postinoculation. One male in the testosterone, long-day treatment group had EEEV viral RNA in a cloacal swab collected on 18 January 2008. Otherwise, no other catbirds exhibited reactivated infections in cloacal swabs or blood. Antibody titers fluctuated over the course of the study, with lowest titers observed in January 2008, which corresponded with the lowest mean weight of the birds. No EEEV viral RNA was detected in the blood, kidney, spleen, brain, liver, and lower intestine upon necropsy at 19 wk postinfection.
东部马脑炎病毒（EEEV；黄病毒科，甲病毒属）疫情不常见，但它可导致受感染的马和人类死亡率高。尽管 EEEV 对人类和动物健康很重要，但人们对该病毒如何越冬以及每年春天重新开始传播知之甚少，特别是在温带地区，感染的成年蚊子不太可能在冬季存活。一种解释该病毒年复一年持续存在的机制的假设是，禽储主体内潜伏病毒的春季复发。在这项研究中，我们用 2007 年 7 月至 8 月在俄亥俄州北部捕获的灰噪鸦（Dumatella carolinensis）来检验这种病毒复发假说。这些鸟于 2007 年 10 月 1 日接受 EEEV 实验性感染。2008 年 1 月，它们被暴露于外源性睾酮和/或延长光照周期，以启动潜伏的 EEEV 感染的再激活。所有鸟类均出现 EEEV 血症，接种后 1 天的平均血清蚀斑形成单位/ml 为 6.0log10。在睾酮、长日照处理组的 1 只雄性中，在 2008 年 1 月 18 日采集的泄殖腔拭子中检测到 EEEV 病毒 RNA。否则，其他灰噪鸦在泄殖腔拭子或血液中均未显示出重新激活的感染。在研究过程中，抗体滴度波动，2008 年 1 月观察到最低滴度，与鸟类体重最低相对应。在感染后 19 周剖检时，在血液、肾脏、脾脏、大脑、肝脏和下肠中均未检测到 EEEV 病毒 RNA。
