Climate and Environmental Influences on the Ecology of Vectors and Vector-borne Diseases

摘要

Recently researchers have recognized the potential effects of climate variability and climate change on infectious disease ecology. Mosquito-borne diseases are of considerable concern due to their reliance on temperature to regulate vector reproduction, survival, and vector and agent development. Precipitation is also influential because it helps maintain habitat for immature mosquitoes. The interactions between climate, vector, and agent are complex, however, and thus assessing the overall impact of climate on disease occurrence is difficult. Discerning the influence of climate on mosquito-borne diseases requires an interdisciplinary synthesis of knowledge about the relationships between components of the disease system and analysis techniques that account for the individual and interacting roles that each element contributes to the ecology of the disease. In this dissertation, climate and climate change influences on dengue fever and West Nile virus are identified through process based modeling to simulate changes in vector and viral transmission dynamics. Analysis of the literature pertaining to climate influences on dengue virus ecology reveals that climate variables often interact interdependently to influence dengue virus transmission. Statistical techniques correlating or modeling climate-dengue relationships are often inconsistent and location specific. Process based modeling has been employed to better simulate the intricacies and non-linear dynamics involved, but most models focus only on vector populations. Therefore, models should incorporate viral development and transmission components to better simulate dengue virus ecology. A model of West Nile virus vector dynamics across the southern United States reveals that impacts from climate change are very location and context-specific. While temperatures generally increase the season length of vector activity, changes in precipitation and evapotranspiration dynamics often lead to lower summer mosquito populations and limited population development in water-stressed areas. A simulation of dengue fever cases in San Juan County, Puerto Rico with a coupled vector-epidemiological model showed strong agreement when compared with reported case data (Willmott's d = 0.90 and r2 = 0.71). The model indicates that certain climate variables became disease limiting during specific times of the year. Temperature limits virus transmission during the winter by slowing viral development while lower precipitation limits spring transmission by suppressing vector populations.