Cellular and Molecular Biology Program, ICBM, Faculty of Medicine, University of Chile, Casilla, Santiago, Chile.
J Med Entomol. 2019 Sep 3;56(5):1384-1388. doi: 10.1093/jme/tjz124.
The etiologic agent of Chagas disease, Trypanosoma cruzi, is transmitted by hematophagous insect vectors that subsist on repeated blood meals over their lives separated by periods of fasting. Using naturally infected Mepraia spinolai, we measured the influence of parasite infection on this host vector's mortality during regular feeding and after fasting. After their capture, the insects were fed twice with uninfected mice to evaluate parasitic infection in their fecal samples by microscopic observation and PCR. Then the insects were subjected to a fasting period, followed by a third (final) feeding. After each feeding, a fecal sample was obtained to evaluate T. cruzi infection. To determine its progress through ontogeny, mortality and ecdysis of the infected and uninfected nymphs and adults were recorded on three occasions, over 140 d, and analyzed. Detections of infection by T. cruzi between the two first feedings increased, but this detection level was generally reduced after final feeding unless reinfected. For nymphs (stages III-V), their mortality was highest when infected after the fasting period, whereas adults were equally resistant to death after fasting when infected with T. cruzi. Metacyclic trypomastigotes were principally excreted in the fecal samples. Our results confirm that T. cruzi is pathogenic to its invertebrate hosts under nutritional stress conditions, when nymphs' mortality is higher while infected than uninfected when they were hungry. These results are epidemiologically important because T. cruzi harms the fasting vector M. spinolai, reducing its lifespan and competence as a disease vector, and thereby its rates of parasite transmission.
恰加斯病的病原体克氏锥虫通过吸血昆虫传播，这些昆虫在其生命周期中通过反复吸血来维持生命，其间会有禁食期。我们使用自然感染的 Mepraia spinolai 来衡量寄生虫感染对宿主昆虫在正常进食和禁食后死亡率的影响。在捕获昆虫后，用未感染的老鼠喂养它们两次，通过显微镜观察和 PCR 评估它们粪便样本中的寄生虫感染情况。然后，让昆虫禁食一段时间，再进行第三次（最后一次）喂养。每次喂养后，都会取粪便样本以评估 T. cruzi 感染情况。为了确定其在个体发育过程中的进展，记录了感染和未感染的若虫和成虫的死亡率和蜕皮情况，共进行了三次，历时 140 天，并进行了分析。在最初的两次喂养之间，感染 T. cruzi 的检测率增加了，但在最后一次喂养后，这种检测水平通常会降低，除非再次感染。对于若虫（III-V 期），在禁食后感染时死亡率最高，而在感染 T. cruzi 后禁食的成虫死亡率则相等。循环型锥鞭毛体主要从粪便样本中排出。我们的研究结果证实，在营养压力条件下，T. cruzi 对其无脊椎宿主是致病的，当饥饿时，感染的若虫死亡率高于未感染的若虫。这些结果在流行病学上很重要，因为 T. cruzi 会损害禁食的媒介 M. spinolai，降低其寿命和作为疾病媒介的能力，从而降低寄生虫的传播率。
