MULTIPLE BLOOD FEEDING BY MOSQUITOES

每日存活概率和人类吸血频率是蚊子在病原体传播中作用的两个最敏感的因素。大多数媒介传播疾病的模型认为，生存和取食行为不会随着蚊子年龄的增长而改变。到目前为止，这一假设没有受到强烈挑战，因为没有准确的方法来估计蚊子一生中不同流行病学阶段的年龄，也没有准确的方法来识别蚊子叮咬过的人；很难或不可能测量蚊子的年龄段和寄主摄食模式。我们已经开发了新的、更准确的方法，可以第一次确定随着蚊子媒介变老和感染，宿主接触的存活率和频率是否会增加。在这项更新建议中，我们将使用这些方法来检验这样一个假设，即埃及伊蚊的每日存活概率和人类觅血频率随着蚊子年龄的增长而增加。年长女性Ae.埃及伊蚊在流行病学上是最重要的，因为它们比年轻的蚊子更容易感染和传播登革热病毒。为了确定大约21日龄的野生蚊子的年龄，我们分析了角质碳氢化合物(CH)。我们可以通过DNA指纹识别蚊子进食的人(S)(S)来重建蚊子的觅血行为。在标记-再捕获研究中的高再捕获率(约30%)使我们能够调查自由放养的蚊子在自然环境中的生存、扩散和觅血。我们的研究有两个具体目标，我们将在泰国西北部进行。埃及伊蚊传播的登革热病毒是地方性的。在目标1中，我们将把观察到的野生蚊子的年龄结构(CH年龄分级)和取食模式(DNA指纹)与预期的模式进行比较，该模式假设这些传播成分随着蚊子年龄的增长保持不变。在直接测试我们在目标2中的研究假设之前，我们将定义我们当前标记-重新捕获方法的局限性，并为后续关于存活、扩散和吸血方面的年龄差异的实验选择最佳程序。在我们的最后一组实验中，我们将通过释放两个不同的年龄队列，并比较它们的重新捕获率、存活率和觅血行为，直接测试生存动态和觅血频率随着蚊子年龄的增加而增加的想法。每次实验结束时的杀虫剂处理将在蚊子感染和传播病毒之前杀死任何幸存的被释放的蚊子。

Daily probability of survival and frequency of human blood- feeding are the 2 most sensitive components of a mosquito's role in pathogen transmission. Most models of vector-borne diseases assume that survival and feeding behavior do not change as mosquitoes grow older. Until now this assumption has not been strongly challenged because accurate methods for estimating age across epidemiologically different portions of a mosquito's lifetime or identifying the people a mosquito had bitten were not available; measurement of mosquito chronological age and host- feeding patterns were difficult or impossible. We have developed novel, more accurate methods that can determine for the 1st time if survival and frequency of host contact increase as mosquito vectors grow older and become infective. In this renewal proposal we will use these methods to test the hypothesis that Aedes aegypti's daily probability of survival and frequency of human blood-feeding increase as mosquitoes age. Older female Ae. aegypti are epidemiologically most important, because they are more likely to be infected with and transmit dengue virus than younger mosquitoes. To determine the chronological age of wild mosquitoes up to approximately 21 days of age we analyze cuticular hydrocarbons (CH). We can reconstruct mosquito blood- feeding behavior with a DNA fingerprinting procedure that identifies the person(s) from which a mosquito took its meal(s). High recapture rates in mark-recapture studies (approximately 30 percent) allow us to investigate survival, dispersal, and blood- feeding for free-ranging mosquitoes in the natural environment. Our study has 2 specific aims that we will carry out in northwestern Thailand, where Ae. aegypti-borne dengue virus is endemic. In Aim 1 we will compare the observed age structure (CH age-grading) and feeding patterns (DNA fingerprinting) of wild mosquitoes to the patterns expected under the assumption that these components of transmission remain constant as mosquitoes grow older. Before directly testing our research hypothesis in Aim 2 we will define the limitations of our current mark- recapture methods and select the best procedure for subsequent experiments on age-dependent differences in survival, dispersal, and blood-feeding. In our last set of experiments we will directly test the idea that dynamics in survival and blood- feeding frequency increase with mosquito age by releasing 2 distinct age cohorts and comparing their recapture rates, survival, and blood-feeding behavior. Insecticide treatments at the end of each experiment will kill any surviving released mosquitoes before they could become infective and transmit virus.