Molecular Occurrence, Diversity and Ecological Patterns of Bartonella spp. in Cave-Dwelling Bats and Associated Streblid Flies

Bats are important reservoirs of vector-borne bacteria, including species of Bartonella, yet the ecological mechanisms underlying their circulation in bat–ectoparasite systems remain poorly understood. Here, we investigated the molecular occurrence, diversity, ecological drivers, and interaction structure of Bartonella spp. in cave-dwelling bats and their associated streblid flies in northeastern Brazil. A total of 492 bats were captured across six caves, from which 231 blood samples and 1017 streblid flies were collected. Molecular screening for Bartonella was performed using a qPCR targeting the 16S–23S rRNA intergenic region, followed by characterization with multiple molecular markers (ftsZ, gltA, ribC, and rpoB). Phylogenetic and genotype diversity analyses revealed high genetic diversity, including lineage clustering with previously described bat-associated Bartonella and ftsZ sequences related to ruminant-associated lineages. Ten genotypes were shared across caves, indicating broad spatial circulation. Generalized linear models showed that streblid load did not predict infection in bats, whereas detection varied significantly among streblid species. Network analyses revealed low specialization of Bartonella molecular markers in bats and significantly higher specialization in flies compared to null expectations. Overall, Bartonella dynamics in cave bats were not explained by streblid abundance alone but instead reflect the combined influence of host ecology, ectoparasite identity, and interaction structure.