Molecular Detection of Filarioid Nematodes in Bats from the Western Brazilian Amazon.

PURPOSE: Filarial nematodes (Onchocercidae) infect diverse mammals, but their occurrence and molecular diversity in Amazonian bats remain poorly documented. We investigated bat-associated filarioids in urban and peri-urban forest fragments in Rio Branco, Acre, western Brazilian Amazon. METHODS: Between December 2022 and October 2023, bats were captured with mist nets in five forest fragments and identified morphologically. Blood was screened for microfilariae by thin smear and microhematocrit. A mitochondrial 12 S rRNA fragment (~ 330 bp) was amplified, and PCR-positive products were Sanger sequenced. Consensus sequences were assessed by BLASTn; after alignment and trimming, 300 nucleotide positions were retained for pairwise p-distance analysis and maximum-likelihood phylogenetic inference (HKY + G; 1,000 bootstraps). RESULTS: Ninety bats representing 20 species, 13 genera, and four families were captured. Microfilariae were detected in 2/90 bats (2.2%): Artibeus planirostris and Tonatia maresi. UDV06 (PZ124269), from A. planirostris, showed strong affinity with Litomosoides, with ~ 98-99% BLASTn identity, complete query coverage, low divergence, and clustering within the genus. HF17 (PZ124268), from T. maresi, showed only ~ 87-88% identity to available Litomosoides sequences and a markedly divergent phylogenetic position, supporting its conservative treatment as an unresolved member of Onchocercidae. CONCLUSION: These findings document bat-associated filarioid occurrence and molecular diversity in the western Brazilian Amazon. UDV06 is supported as Litomosoides at the genus level, whereas HF17 remains unresolved within Onchocercidae. Additional mitochondrial, particularly cox1, and nuclear markers are needed for improved taxonomic resolution.