Tick-associated microorganisms (Borrelia, Rickettsia, Hepatozoon, and Hemolivia) in Amblyomma varanense ticks parasitizing Asian water monitors (Varanus salvator): Insights from a hotspot in Ratchaburi Province, Western Thailand

Asian water monitors ( Varanus salvator ) serve as significant hosts for ticks in Southeast Asia, yet the diversity of microorganisms potentially vectored or endosymbiotic within their ticks in Western Thailand remains underexplored. This study investigated the occurrence and genetic diversity of tick-associated microorganisms in ticks parasitizing this varanid species at the Khaozon Wildlife Breeding Center (KWBC), Ratchaburi Province. Morphological and molecular analyses confirmed that all 30 adult ticks collected were Amblyomma varanense (Arachnida: Ixodidae). PCR-based analysis coupled with DNA sequencing revealed that Rickettsia was the most prevalent microorganism detected (90.0%, 27/30), with gltA sequences genetically clustering within the spotted fever group (SFG) and closely related to the human pathogenic Rickettsia monacensis and Rickettsia tamurae . Utilizing the flaB gene, Borrelia spp. were identified in 76.66% (23/30) of ticks, forming lineages within the reptile-associated (REP) clade, distinct from Lyme borreliosis (LB) group. Furthermore, Hepatozoon sp. and Hemolivia sp. were each identified in 3.33% (1/30) of ticks; notably, this represents the first molecular record of Hemolivia sp. in A. varanense from a varanid host. Nevertheless, this discovery relies on a single genetic marker (18S rRNA gene). Our study revealed a diverse microbial community in varanid-associated A. varanense ticks at the KWBC. Despite the absence of human infections by reptile-associated Borrelia spp. and Rickettsia spp., the existence of these microorganisms underscores the critical need for ongoing One Health surveillance at this anthropogenic-forest interface. • Amblyomma varanense was the sole tick species found on Varanus salvator. • Four genera of tick-associated microorganisms were detected in A. varanense. • Borrelia lineages formed a unique reptile-associated clade distinct from Lyme group. • Rickettsia sp. was the major microorganism detected and may function as primary endosymbiont of ticks. • First molecular detection of Hemolivia sp. in A. varanense from a varanid host.