Malkinson M, Banet C
Kimron Veterinary Institute, Beit Dagan 50250, Israel.
Curr Top Microbiol Immunol. 2002;267:309-22. doi: 10.1007/978-3-642-59403-8_15.
Surveys on wild birds conducted during the last two decades in Europe, notably Poland and the Czech Republic, to determine their infection rate with WN virus have revealed endemic foci of infection. Some species of seropositive birds were nonmigrators while others were hatchlings of migrating species. Persistently infected avian reservoirs are potential sources of viruses for mosquitoes that multiply in the temperate European zone in hot, wet summers. In the past, evidence for geographical circulation of WN viruses was based on antigenic analysis of strains from different countries while more recent epidemiological studies have relied on analysis of nucleotide sequences of the envelope gene. With the reappearance of epidemic WN fever in European countries, interest has been focused once again on the African origin of the causal agent carried by migrating wild birds. In some epidemics, isolates were made from human cases or mosquitoes and only serologic evidence for infection was available from domestic and wild bird populations. In this respect the unusual findings of anti-WN virus antibodies in a population of storks maintained in northern Germany could be interpreted as evidence for local infection. The unique susceptibility of young domestic geese in Israel in 1997-2000 to WN virus and the isolation of similar strains from migrating White storks in Israel and Egypt suggest that the recent isolates are more pathogenic for certain avain species and that migrating birds do play a crucial role in geographical spread of the virus. Knowledge of the routes taken by birds migrating between Africa and Europe will therefore help in selecting sites where attempts to isolate viruses will be most fruitful. The appearance of the disease in western European equine populations (Italy and France) requires that other birds and their migratory routes be investigated once more. It remains to be determined whether the European endemic foci of WN virus are in themselves sources of infection for other birds that migrate across Europe and do not necessarily reach sub-Saharan Africa. If this is the case it will be necessary to define the strategies for detection of virus overwintering in the European temperate climate.
在过去二十年里，欧洲（尤其是波兰和捷克共和国）对野生鸟类进行了调查，以确定它们感染西尼罗病毒的比率，结果发现了地方性感染病灶。一些血清呈阳性的鸟类是留鸟，而其他一些则是候鸟的幼雏。持续感染的鸟类宿主是病毒的潜在来源，这些病毒会在欧洲温带地区炎热潮湿的夏季在蚊子体内繁殖。过去，西尼罗病毒地理传播的证据基于对来自不同国家毒株的抗原分析，而最近的流行病学研究则依赖于对包膜基因核苷酸序列的分析。随着西尼罗热在欧洲国家再次出现，人们的兴趣再次集中在迁徙野生鸟类携带的病原体的非洲起源上。在一些疫情中，从人类病例或蚊子中分离出了毒株，而关于家养和野生鸟类群体的感染情况仅有血清学证据。在这方面，在德国北部饲养的一群鹳中发现抗西尼罗病毒抗体这一不寻常的发现，可以被解释为当地感染的证据。1997年至2000年以色列幼龄家鹅对西尼罗病毒具有独特的易感性，以及在以色列和埃及的迁徙白鹳中分离出相似毒株，这表明最近分离出的毒株对某些鸟类物种更具致病性，并且迁徙鸟类在病毒的地理传播中确实起着关键作用。因此，了解鸟类在非洲和欧洲之间迁徙的路线，将有助于选择最有可能成功分离病毒的地点。西尼罗病毒在西欧马群（意大利和法国）中出现，这就需要再次对其他鸟类及其迁徙路线进行调查。西尼罗病毒在欧洲的地方性病灶本身是否是穿越欧洲且不一定到达撒哈拉以南非洲的其他鸟类的感染源，仍有待确定。如果是这样，就有必要确定在欧洲温带气候中检测病毒越冬的策略。
