Abstract. Characteristics of Trypanosoma cruzi infection were studied in a rural area of the eastern plains of Colombia. Using enzyme-linked immunosorbent assay and indirect fluorescent-antibody tests, the infection was determined in 11.6% of the inhabitants of 142 dwellings. During 6 months of community surveillance, in 42.3% dwellings, 609 triatomines were collected (597 Rhodnius prolixus and seven, three, one, and one of Panstrongylus geniculatus, Psammolestes arturi, Eratyrus mucronatus, and Triatoma maculata, respectively). Rhodnius prolixus was found in 80% peridomiciliary Attalea butyracea palms examined with baited traps, and its infection with T. cruzi was 30% and 38.5% in dwellings and palms, respectively. Trypanosoma cruzi was isolated in five of 35 triatomines and in one of 24 dogs. The blood of domestic and wild animals was identified in triatomines collected in the intradomicile and in palms. These results support the extension of the wild cycle of T. cruzi to human dwellings and the characterization of a new scenario for transmission in Colombia.Trypanosoma cruzi infection continues to affect nearly 6 million people in 21 countries of the Americas 1 despite the success of control programs against domestic triatomines. 2There are zones where dwellings are infested by other species of Triatominae with peridomiciliary and wild ecotopes. In the Amazon, some of the more than 27 wild species described, principally of the genus Rhodnius, have made incursions into dwellings, with the risk of infecting human populations. 3In Colombia, the Andean region in the eastern zone below 2,000 m above sea level has been considered endemic for Chagas disease because of the high degree of domiciliary infestation, wide dispersion, and the high densities of Rhodnius prolixus.4,5 A decade after the adoption of a government program to control domiciliary triatomines, in our observation, this species has been controlled. However, another transmission scenario has begun to be known with checking of the wild cycle in peridomiciliary palms as a transmission risk factor in the departments of the eastern plains 6 and the reporting of high prevalence rates of human infection with T. cruzi.7 This study was conducted for the purpose of clarifying the epidemiological characteristics of this scenario in this region.In December 2008, the prevalence of T. cruzi infection was evaluated in the inhabitants of 142 dwellings in the department of Casanare, dispersed in rural areas of the municipalities of Maní (04°49′02″N/72°17′19″W) and Aguazul (05°10′23″N/ 72°33′17″W), which were fumigated by the program of VectorTransmitted Diseases (Enfermedades Transmitidas por Vectores [ETV], in Spanish) in that department. This territory corresponds to the alluvial and eolic plains of the Orinoquía, composed of flooded savannas with herbaceous and graminaceous vegetation in the humid warm thermal floor, with an average temperature of 25-27°C and an annual rainfall of 2,400-2,600 mm (Figure 1).The dwellings are constructed with brick walls, cement, ti...