Chagas disease (American Trypanosomiasis), caused by Trypanosoma cruzi and transmitted by triatomine bugs, is the most important vector-borne disease in Latin America. Despite an ongoing eradication campaign, transmission persists in much of the continent, particularly in the Gran Chaco of northern Argentina, Paraguay and Bolivia, where Triatoma infestans is the main vector. Abundant peridomestic structures (particularly animal corrals) provide a refuge and source for repeated domestic reinfestation, dogs are a continuous source of infection for colonizing triatomine bugs, and sylvatic vectors invading human habitations may also play a role in reintroducing T. cruzi. The long-term goal of this project is to interrupt the reinfestation process and introduction of infection into homes. High degree of spatial, temporal and host heterogeneity with regard to vector and parasite survival, reproduction and spread, and ongoing anthropogenic changes have to be considered to understand infestation and infection patterns. Data derived from molecular tools, satellite imagery and field observations and experiments will be integrated into a GIS and mathematical models to elucidate the underlying biological mechanisms and epidemiological processes. The Specific Aims of the project are: 1) To analyze the spatial and temporal pattern of reinfestation by triatomine bugs and distribution of T. cruzi infection in bugs, dogs and people in three rural communities with the aid of satellite imagery, GIS, spatial statistics and other analytical tools; 2) To identify mechanisms underlying these patterns using field observations, field manipulations and experimental studies, and relate changes in these patterns to management strategies, habitat degradation and other anthropogenic changes; 3) To determine the source of colonizing vectors and T. cruzi infection by comparing the genetic makeup of bug and parasite strains using molecular techniques and morphometry; 4) To develop an empirically based, spatially structured mathematical model of the reinfestation and transmission process at the community-wide level; 5) On a coarser scale, to apply the results and develop risk maps of the distribution of household infestation by T. infestans and T. cruzi infection at the village, Department and Province-wide level; to compare effects of standard vs. scientifically designed intervention programs on infestation level and rate of reinfestation in new communities; and 6) To train scientists and NVCP personnel in the use of ecological and epidemiological tools, modeling, GIS and remote sensing techniques for research design and focused control strategies.