Mitochondrial genome characterization of a Reticulinasus sp. (Argasidae: Ornithodorinae) parasitizing bats in Thailand.

BACKGROUND

Second only to mosquitoes, ticks (Acari: Ixodida) are significant blood-feeding ectoparasites and vectors of numerous pathogens affecting both animals and humans. Despite bats serving as hosts to various tick species, they remain relatively understudied due to their nocturnal behavior and laborious capture procedures. Soft ticks in particular display diverse ecological behaviors, inhabiting bat roosts, caves, and occasionally human dwellings. This overlap in habitats suggests soft ticks may play a critical role as vectors of zoonotic pathogens. In Southeast Asia, research on soft ticks has primarily focused on island nations, with limited studies on bat-associated ticks in Thailand. This study aimed to examine the identity and distribution of bat ticks in Thailand.

METHODS

Bats were captured across ten provinces in Thailand between 2018 and 2023. Ticks were removed from the bats' skin and identified through morphological examination using a stereomicroscope, with molecular confirmation. Scanning electron micrographs were recorded. Prevalence, mean abundance, and mean intensity of tick infestations were calculated. The mitochondrial genomes of the ticks were sequenced, annotated, and subjected to phylogenetic analysis.

RESULTS

A total of 1031 bats, representing 7 families, 11 genera, and 28 species, were captured. Tick infestations were found in 34 bats (3.30%), specifically in two species: Craseonycteris thonglongyai (33/139, 23.74%) and Eonycteris spelaea (1/2, 50%). All ticks were in the larval stage. Basic local alignment search tool for nucleotide (BLASTN) searches using 16S rRNA (425 bp) and COI (825 bp) sequences, along with Barcode of Life Database (BOLD) database queries, revealed the highest similarity to tick in the genus Reticulinasus found on bats in Zambia. The mitochondrial genomes of ticks collected from C. thonglongyai and E. spelaea were 14,433 bp and 14,439 bp in length, respectively, and contained 13 protein-coding genes, 22 tRNA genes, and 2 rRNA genes. Phylogenetic analysis placed these ticks within the Reticulinasus clade, with strong support indicated by high bootstrap values.

CONCLUSIONS

This study identified Reticulinasus sp. infestations on C. thonglongyai and E. spelaea bats, marking the first report of soft ticks in bats from Thailand, with potential implications for zoonotic disease transmission.