Molecular detection and genetic diversity of Ehrlichia spp. in bats and bat-associated Reticulinasus soft ticks in Thailand.

Ehrlichia is a genus of Gram-negative, obligate intracellular bacteria that causes ehrlichiosis in a wide range of domestic and wild animals and is primarily transmitted by ticks. Although Ehrlichia species have been reported in numerous vertebrate hosts, their occurrence in bats remains poorly understood. Thailand, located within the Indo-Burma Biodiversity Hotspot and home to more than 146 bat species, provides an ideal setting for investigating bat-associated microorganisms. This study investigated the molecular prevalence and genetic diversity of Ehrlichia spp. in bats and bat-associated ticks in Thailand. A total of 435 samples, comprising 387 blood samples from 28 bat species and 48 pooled Reticulinasus sp. tick samples, were collected between February 2018 and February 2023. These samples were screened using nested PCR assays targeting the groEL (1070 bp) and 16S rRNA (630 bp) genes, followed by Sanger sequencing. Species identity was assessed by BLASTn, and phylogenetic relationships were inferred using maximum likelihood analysis. Ehrlichia DNA was detected in 5.7% (22/387; 95% CI: 3.6-8.5%) of bats. For tick samples, the minimum infection rate (MIR) based on pooled testing was 4.17% (4/48 pools; 95% CI: 1.15-10.31%). Positive ticks were collected from Craseonycteris thonglongyai and Eonycteris spelaea. Sequence analyses showed the highest similarity to Candidatus Ehrlichia shimanensis and related Ehrlichia spp. from Japan, Australia, and China (92.06%-92.49% for the 16S rRNA gene and 97.26%-98.11% for the groEL gene). Phylogenetic analyses based on 16S rRNA and groEL genes resolved the sequences into two distinct clades, suggesting previously uncharacterized Ehrlichia lineages. These findings provide the first molecular evidence for Ehrlichia spp. in bats and bat-associated ticks in Thailand and underscore the need for genomic studies to clarify their taxonomy, evolutionary relationships, host associations, and ecological significance.