Survey of sand fy fauna in six provinces of Southern Vietnam with species identifcation using DNA barcoding

Background Sand fies, belonging to the Psychodidae family, represent small, hairy insects that serve as signifcant
vectors in various important medical and veterinary diseases. Despite being recognized by the World Health Organization as an endemic area for leishmaniasis, Southeast Asia lacks comprehensive information on the species composition and biology of sand fies. To address this, the current study aimed to survey sand fy biodiversity. Methods Sand fies from six provinces in Southern Vietnam were collected using CDC light traps. Sand fies were subsequently identifed morphologically and confrmed molecularly using mitochondrial cytochrome oxidase c subunit I (COI) and cytochrome b (cytb) sequences. BLASTN searches were conducted, and the species identity of sand fies was further confrmed through a Barcode of Life Database (BOLD) search utilizing COI sequences. Subsequently, nucleotide sequences were subjected to a panel of analyses including intraspecifc variation, phylogenetic relationships and haplotype network. The average densities of collected sand fies (sand fies/trap/night) and species richness were also recorded. Results A total of 753 sand fies were collected. After excluding damaged specimens, six sand fy species, namely Phlebotomus stantoni, Sergentomyia khawi, Se. silvatica, Se. barraudi, Se. bailyi and Grassomyia indica, were identifed. All conspecifc sand fy sequences, including Ph. stantoni, Se. barraudi, Gr. indica, Se. bailyi, Se. khawi and Se. silvatica, clustered with their reference sequences, corroborating the results of morphology-based identifcation, BLASTN analysis and BOLD search. For intraspecifc variation of sand fies obtained from the current study, COI diversity indices were consistently higher than those of cytb. Conclusions This study provides the frst updates on morphological and molecular characterization of sand fies
in Southern Vietnam. This acquired knowledge on sand fy species composition is essential for controlling sand fyborne diseases in this potentially endemic region.