Phlebotomine sand fly distribution, abundance and pathogen associations in Thailand: a scoping review

Phlebotomine sand flies are found across multiple regions of Thailand, with growing recognition of their role in transmitting zoonotic pathogens. Environmental factors, including climate variability and vector ecology, may influence their distribution and activity, contributing to the potential spread of zoonotic pathogens in Southeast Asia. However, comprehensive data on sand fly distribution in Thailand remain limited. To address this gap, a systematic review was conducted following PRISMA guidelines. Out of 112 records retrieved, 33 met the inclusion criteria and quality assessment for further analysis. As per results, sand flies are widespread in Thailand, with a high level of species diversity comprising 42 species of 6 different genera. However, several provinces lack data on the presence and distribution of sand flies. Eleven species were identified as the overall abundant species throughout the studies from January 2007 to June 2025 and grouped by abundance: low-abundance species (Sergentomyia barguesae, Sergentomyia phadangensis, Sergentomyia barraudi and Sergentomyia indica), abundant but understudied species (Sergentomyia sylvatica, Sergentomyia anodontis and Neopulpus vietnamensis) and most abundant species (Sergentomyia hodgsoni, Sergentomyia gemmea, Sergentomyia iyengari and Sergentomyia khawi). From the most abundant species, S. khawi tested positive for several pathogens, such as Leishmania spp., Trypanosoma spp., Bartonella spp. and orbivirus. Besides, S. khawi has been shown to exhibit human-biting behaviour through the analysis of blood meal. These findings raise concerns about its potential role in pathogen transmission, especially concerning zoonotic pathogens. However, vector competence remains unproven for some of these pathogens, suggesting the need for further research.