Forest fragment size shapes Trypanosoma cruzi transmission and vector-host dynamics in eastern Colombia.

Chagas disease, caused by the protozoan Trypanosoma cruzi, remains a major public health challenge in Latin America. Its transmission dynamics are tightly governed by ecological factors that influence vector-host interactions. Habitat fragmentation and land-use change disrupt sylvatic environments, forcing triatomine vectors to adapt to peridomestic settings, thereby increasing human-vector contact and modifying host availability. This study assesses how forest patch size influences T. cruzi transmission in three Attalea butyracea-dominated forest fragments of varying sizes (Canagüey: 109 ha, El Samán: 79 ha, La Dorada: 46 ha) in Casanare, eastern Colombia. Triatomines were collected using live-bait traps in 266 of the 330 sampled palms, and mammals were captured along edge and interior transects. A total of 2758 Rhodnius prolixus were collected, with the largest patch harboring the highest abundance. Among 1247 vectors analyzed by molecular methods, 91.48 % were infected with T. cruzi, exhibiting significant differences in parasite load among patches. Blood meal analysis using 12S rRNA gene amplicon sequencing revealed similar food sources across all vector developmental stages and forest sizes. Of the 147 mammals sampled, 6.8 % were infected in the smaller areas, while no infected mammals were found in the large forest, suggesting a higher parasite transmission in smaller forest fragments. These findings suggest that the forest fragments size influence the population concentration of triatomines and may facilitate increasing the risk of transmission of T. cruzi. Our results highlight the complex ecological interactions driving T. cruzi transmission and underscore the need for landscape-scale surveillance and targeted control measures to reduce the risk of parasite transmission in regions undergoing intense anthropogenic change.