Molecular surveillance of bat flies (Diptera: Nycteribiidae and Streblidae) and other ectoparasites in Ratchaburi, Thailand: Unraveling host associations and coronavirus transmission dynamics in the context of zoonotic spillover risk

Abstract

Background: Bats act as hosts for various ectoparasites, including bat flies, bugs, fleas, ticks, and mites, which play crucial roles in the transmission of bat-borne pathogens. As obligate blood-feeding parasites, these ectoparasites can serve as direct vectors or indirectly influence pathogen dynamics in bat populations. In Thailand, molecular studies on bat ectoparasites are limited, with scarce data on their diversity, distribution, and role in zoonotic pathogen transmission. This study aims to provide the first molecular characterization of bat flies and other ectoparasites in Ratchaburi, Thailand, focusing on their blood meals and potential involvement in coronavirus transmission. Methods: Ectoparasites were identified using the cytochrome oxidase I (COI) gene, while host blood meals were confirmed using the cytochrome b (CytB) gene. A total of 37 bat flies and additional ectoparasites (ticks and flea) were analyzed. Coronavirus screening was conducted through targeted amplification of the RNA-dependent RNA polymerase (RdRp) gene, followed by sequencing and phylogenetic analysis of positive samples. Results: Three bat fly genera were identified: Nycteribia sp. (20), Phthiridium sp. (15), and Raymondia sp. (2). Blood meal analysis indicated host associations with Rhinolophus coelophyllus for Nycteribia sp., R. pusillus and Chaerephon plicatus for Phthiridium sp., and R. pusillus for Raymondia sp. Additionally, two Ixodes sp. ticks and one Hystrichopsylla sp. flea were found, all associated with C. plicatus. Coronavirus screening identified positive samples, with sequencing revealing alphacoronaviruses and betacoronaviruses. Conclusions: This study highlights the importance of molecular tools in characterizing ectoparasites, their blood meal sources, and associated pathogens. It underscores the potential of ectoparasites as non-invasive tools for coronavirus detection in bats, addressing knowledge gaps and contributing to public health strategies for mitigating zoonotic spillover risks.