This project develops detailed, spatially explicit models for the several sylvatic transmission cycles of Trypanosoma cruzi, which causes Chagas' disease, interacting in the U.S. and northern Mexico, which have been little studied at the population level. Differences in parasite strain, host and vector species (primarily raccoons, opossums, and woodrats, and the insect vectors Triatoma sanguisuga and gerstaeckeri), and their characteristics give each cycle distinct dynamics, but vector dispersal couples them together. Climate changes, both long-term and seasonal, affect these dynamics by regulating vector behavior, creating a potential for geographical invasion of non-native strains, while observed cross-immunity between strains in the U.S., together with parasite adaptations particular to each cycle, set up a competition between strains that may allow native (enzootic) strains to form a barrier to such invasion.
The project develops detailed small-scale models (agent-based as well as analytical) to study how local effects (like dispersal) affect global dynamics, detailed large-scale models to study the result-ing global dynamics, with classical metapopulation models (dynamical systems with both ordinary and stochastic differential equations) as a baseline from which to derive not only the more detailed models but also qualitative analytical and probabilistic results which can be used to anticipate and interpret numerical results. Four structural phases of the project develop corresponding models at low and high spatial resolution on local and regional scales, while overlaid across all model frameworks is the study of climate effects on vector feeding, maturation, mobility, and subsequent infection rates. The mathematical focus of the project is the development of a multi-level modeling approach in which local and global factors influence each other, while the biology centers around the need to understand the complex interactions between the evolutionary adaptations to different transmission avenues (stercorarian, vertical and oral) made by T. cruzi in response to local vector behavior, changes in vector behavior driven by differences in temperature and humidity, and the communications between transmission cycles caused by dispersal. The research not only answers the specific questions posed relative to these models and biological systems, but also provides an important case study in the areas of emerging/re-emerging vector-borne diseases, multiscale modeling, and ecosystem responses to climatic change.
This work involves a multidisciplinary and international collaboration with cooperating researchers in Georgia (U.S.), France and Mexico with expertise in vector population biology, evolutionary adaptations, land use and public health issues, and various aspects of modeling, as well as with undergraduate and graduate students and a postdoctorate researcher who will gain training in interdisciplinary collaborative research and mentoring skills while working on the project.
