Trypanosoma infection and bloodmeal analysis in post-feeding sand flies across Thailand

Phlebotomine sand flies are recognized as a primary vector of Leishmania and are also suspected vectors of Trypanosoma. The transmission cycle of these parasites relies on the distribution of sand fly vectors, parasites, and reservoir animals. This study aimed to detect Leishmania and Trypanosoma DNA and identify the sources of bloodmeals in post-feeding sand flies captured across Thailand. A total of 42,911 field female sand flies were collected from 11 provinces across Thailand using CDC light traps. Among these, 253 post-feeding sand flies were selected for analysis. The predominant species in this study was Sergentomyia khawi (33.60 %). The DNA was extracted from individual female sand flies. Polymerase chain reaction (PCR), specific to the internal transcribed spacer 1 (ITS1) and the small subunit ribosomal RNA (SSU rRNA) gene regions were used to detect the presence of Leishmania and Trypanosoma DNA, respectively. Additionally, cytochrome c oxidase subunit I (COI) gene region was utilized to identify the sources of host bloodmeals. Leishmania DNA was not detected in any specimens. The analysis of SSU rRNA sequences revealed the presence of Trypanosoma DNA (11.46 %, 29/253) in sand fly samples. Among these samples, T. noyesi (1.58 %, 4/253) was identified in Idiophlebotomus longiforceps and Phlebotomus asperulus, Trypanosoma Anura01+02/Frog2 (1.18 %, 3/253) in Se. khawi, and Trypanosoma Anura04/Frog1 (8.70 %, 22/253) in Se. khawi, Se. hivernus and Grossomyia indica. Bloodmeal analysis utilizing the COI gene revealed a diverse range of vertebrate hosts' blood, including bird, bat, frog and sun skink. Our findings confirm the presence of Trypanosoma DNA and identify the sources of bloodmeals from vertebrate hosts in various sand fly species, suggesting their potential as possible vectors for Trypanosoma in Thailand. Furthermore, our study is the first to provide molecular evidence using the COI gene to identify frogs as a host blood source for sand flies in Thailand. Further studies focusing on the isolation of live parasites in sand flies to confirm vector potential and examining the role of animal reservoirs will enhance our understanding of the host-parasite relationship and enable more efficient control for disease transmission.