Hidden in plain sight: Discovery of sand flies in Singapore and description of four species new to science

Phlebotomine sand flies (Diptera: Psychodidae) are small, blood-sucking insects that are of significant public and veterinary health importance for their role in the transmission of Leishmania parasites, bacteria and arboviruses. Although sand flies have been documented in most Southeast Asian countries, there are no published records confirming their presence in Singapore. Here, we provide the first documented evidence on the presence of sand flies in Singapore. Using an integrated taxonomic approach that combines morphological analysis with DNA barcoding of the mitochondrial cytochrome b (cytb) and cytochrome c oxidase subunit I (COI) genes, we identified eight sand fly species, including four newly described species - Phlebotomus seowpohi n. sp., Sergentomyia leechingae n. sp., Sergentomyia gubleri n. sp., and Sergentomyia retrocalcarae n. sp.. Phylogenetic analyses suggest that the new Phlebotomus species, belonging to subgenus Euphlebotomus, is closely related to Phlebotomus argentipes, an important vector of Leishmania donovani from the South Asian region. The discovery of phlebotomine sand flies in Singapore underscores the importance of biosurveillance of biting arthropods. Given Singapores status as a major travel hub, there is a potential risk of leishmaniasis being introduced either by residents returning, or visitors arriving from endemic regions. This risk is compounded by the recent detection of local canine leishmaniasis. Thus, continuous monitoring is essential to assess and manage the risk of disease transmission, support the development of an early warning system, and enable timely and targeted public health interventions. The findings from this study contributes to the global knowledge on sand fly and enhance our understanding of local sand fly diversity and distribution. Author SummaryPhlebotomine sand flies are small, blood-sucking insects recognized as significant vectors for various diseases including leishmaniasis. This study provides the first evidence of their presence in Singapore. Using an integrated taxonomic approach combining morphological analysis with DNA barcoding, we identified eight sand fly species that include four new species: Phlebotomus seowpohi n. sp., Sergentomyia leechingae n. sp., Sergentomyia gubleri n. sp., and Sergentomyia retrocalcarae n. sp. The presence of sand flies in Singapore highlights an important biosurveillance need, as the regions status as a major travel hub increases the risk of leishmaniasis being introduced. Importantly, recent findings of canine leishmaniasis in local dogs amplify the threat of disease transmission. Continuous monitoring and understanding of sand fly diversity and ecology are essential for developing effective public health strategies and early warning systems to manage this risk.