Effect of patch size on the occupancy and spatial co-occurrence patterns of Trypanosoma cruzi (Trypanosomatida: Trypanosomatidae), Didelphis virginiana (Didelphimorphia: Didelphidae), and Triatoma dimidiata (Hemiptera: Reduviidae) in human-modified environments.

Chagas disease is caused by Trypanosoma cruzi Chagas, a parasite with a life cycle involving hematophagous triatomines and vertebrate mammals as hosts. The parasite's metapopulation is nested within its biological habitat patches, or hosts. In anthropogenic landscapes, the hierarchical arrangement of territorial units (locality, block, property) complicates the identification of an appropriate geographic patch size to assess parasite and host persistence. In this study, we evaluated local spatial co-occurrence patterns among Triatoma dimidiata (sensu lato) (Latreille), Didelphis virginiana Allen, and T. cruzi using 3 distinct patch sizes: (i) property area (x¯=3115 ± 1.01 m2), (ii) perceptual range of D. virginiana (x¯=16241 ± 5.29 m2), and (3) urban block area (x¯=36473 ± 4.89 m2) averages, replicated across 10 localities in Yucatán, Mexico. A total of 1,437 host individuals were sampled, with infection prevalence reaching 12% in triatomines and 50.1% in opossums. We delineated over 13,000 spatial patches for assessing parasite-host dynamics. Our results showed that block-sized patches had a higher density of hosts and stronger host-parasite interactions, resulting in increased parasite occupancy in a smaller number of patches. While interactions varied more across localities in these patches, most localities exhibited significant spatial autocorrelation in patches defined by the perceptual range of D. virginiana. Co-occurrence patterns were best captured at the urban block scale. Increasing patch size led to a higher probability of non-random spatial co-occurrence, indicating that geographic patch size is a key factor in understanding how the spatial ecology of its hosts affects the distribution and persistence of T. cruzi.