Department of Microbiology, Immunology and Pathology, Colorado State University, 3195 Rampart Road, Fort Collins, CO 80523, USA.
J Med Entomol. 2013 May;50(3):467-78. doi: 10.1603/me12245.
After more than a half century without recognized local dengue outbreaks in the continental United States, there were recent outbreaks of autochthonous dengue in the southern parts of Texas (2004-2005) and Florida (2009-2011). This dengue reemergence has provoked interest in the extent of the future threat posed by the yellow fever mosquito, Aedes (Stegomyia) aegypti (L.), the primary vector of dengue and yellow fever viruses in urban settings, to human health in the continental United States. Ae. aegypti is an intriguing example of a vector species that not only occurs in the southernmost portions of the eastern United States today but also is incriminated as the likely primary vector in historical outbreaks of yellow fever as far north as New York, Philadelphia, and Boston, from the 1690s to the 1820s. For vector species with geographic ranges limited, in part, by low temperature and cool range margins occurring in the southern part of the continental United States, as is currently the case for Ae. aegypti, it is tempting to speculate that climate warming may result in a northward range expansion (similar to that seen for Ixodes tick vectors of Lyme borreliosis spirochetes in Scandinavia and southern Canada in recent decades). Although there is no doubt that climate conditions directly impact many aspects of the life history of Ae. aegypti, this mosquito also is closely linked to the human environment and directly influenced by the availability of water-holding containers for oviposition and larval development. Competition with other container-inhabiting mosquito species, particularly Aedes (Stegomyia) albopictus (Skuse), also may impact the presence and local abundance of Ae. aegypti. Field-based studies that focus solely on the impact of weather or climate factors on the presence and abundance of Ae. aegypti, including assessments of the potential impact of climate warming on the mosquito's future range and abundance, do not consider the potential confounding effects of socioeconomic factors or biological competitors for establishment and proliferation of Ae. aegypti. The results of such studies therefore should not be assumed to apply in areas with different socioeconomic conditions or composition of container-inhabiting mosquito species. For example, results from field-based studies at the high altitude cool margins for Ae. aegypti in Mexico's central highlands or the Andes in South America cannot be assumed to be directly applicable to geographic areas in the United States with comparable climate conditions. Unfortunately, we have a very poor understanding of how climatic drivers interact with the human landscape and biological competitors to impact establishment and proliferation of Ae. aegypti at the cool margin of its range in the continental United States. A first step toward assessing the future threat this mosquito poses to human health in the continental United States is to design and conduct studies across strategic climatic and socioeconomic gradients in the United States (including the U.S.-Mexico border area) to determine the permissiveness of the coupled natural and human environment for Ae. aegypti at the present time. This approach will require experimental studies and field surveys that focus specifically on climate conditions relevant to the continental United States. These studies also must include assessments of how the human landscape, particularly the impact of availability of larval developmental sites and the permissiveness of homes for mosquito intrusion, and the presence of other container-inhabiting mosquitoes that may compete with Ae. aegypti for larval habitat affects the ability of Ae. aegypti to establish and proliferate. Until we are armed with such knowledge, it is not possible to meaningfully assess the potential for climate warming to impact the proliferation potential for Ae. aegypti in the United States outside of the geographic areas where the mosquito already is firmly established, and even less so for dengue virus transmission and dengue disease in humans.
在美国大陆半个多世纪没有被认可的本地登革热疫情之后，德克萨斯州南部（2004-2005 年）和佛罗里达州（2009-2011 年）最近爆发了地方性登革热疫情。这种登革热的再次出现引起了人们的兴趣，即美国大陆黄热病蚊子（埃及伊蚊）未来构成的威胁程度，黄热病蚊子是城市环境中登革热和黄热病病毒的主要媒介。埃及伊蚊是一个有趣的例子，它不仅存在于美国东部最南端，而且在历史上的黄热病疫情中被认为是北至纽约、费城和波士顿的主要媒介，这些疫情发生在 17 世纪 90 年代至 19 世纪 20 年代。对于那些地理范围部分受到美国南部低温和凉爽范围限制的媒介物种来说，如目前的埃及伊蚊，人们很容易推测气候变暖可能导致其分布范围向北扩展（类似于莱姆病螺旋体的伊蚊传播媒介在斯堪的纳维亚和加拿大南部近几十年来的情况）。尽管毫无疑问，气候条件直接影响埃及伊蚊的许多生活史方面，但这种蚊子也与人类环境密切相关，并直接受到产卵和幼虫发育用蓄水容器的可用性的影响。与其他容器栖息的蚊子物种的竞争，特别是白纹伊蚊（斯库塞），也可能影响埃及伊蚊的存在和当地丰度。仅关注天气或气候因素对埃及伊蚊存在和丰度的影响的实地研究，包括评估气候变暖对蚊子未来分布和丰度的潜在影响，没有考虑到社会经济因素或生物竞争者对埃及伊蚊建立和繁殖的潜在混杂影响。因此，此类研究的结果不应假定适用于具有不同社会经济条件或容器栖息蚊子物种组成的地区。例如，在墨西哥高原或南美洲安第斯山脉的埃及伊蚊高海拔凉爽边缘进行的实地研究结果，不能直接应用于美国具有类似气候条件的地理区域。不幸的是，我们对气候驱动因素如何与人类景观和生物竞争者相互作用，以影响埃及伊蚊在其分布范围的凉爽边缘的建立和繁殖，了解甚少。评估这种蚊子对美国大陆人类健康构成的未来威胁的第一步是在美国（包括美墨边境地区）沿战略气候和社会经济梯度进行设计和开展研究，以确定在当前情况下，自然和人类环境的耦合对埃及伊蚊的允许程度。这种方法将需要专门针对与美国大陆相关的气候条件进行实验研究和实地调查。这些研究还必须评估人类景观的影响，特别是幼虫发育场所的可用性以及蚊子入侵房屋的允许程度，以及可能与埃及伊蚊竞争幼虫栖息地的其他容器栖息蚊子的存在，如何影响埃及伊蚊建立和繁殖的能力。在我们掌握这些知识之前，不可能有意义地评估气候变暖对美国以外埃及伊蚊繁殖潜力的影响，也不可能评估登革热病毒传播和人类登革热疾病的潜在影响。
