Abstract
BackgroundPhlebotomine sand flies are vectors of Leishmania spp. At least 27 species of sand flies have been recorded in Thailand. Although human leishmaniasis cases in Thailand are mainly imported, autochthonous leishmaniasis has been increasingly reported in several regions of the country since 1999. Few studies have detected Leishmania infection in wild-caught sand flies, although these studies were carried out only in those areas reporting human leishmaniasis cases. The aim of this study was therefore to identity sand fly species and to investigate Leishmania infection across six provinces of Thailand.MethodsSpecies of wild-caught sand flies were initially identified based on morphological characters. However, problems identifying cryptic species complexes necessitated molecular identification using DNA barcoding in parallel with identification based on morphological characters. The wild-caught sand flies were pooled and the DNA isolated prior to the detection of Leishmania infection by a TaqMan real-time PCR assay.ResultsA total of 4498 sand flies (1158 males and 3340 females) were caught by trapping in six provinces in four regions of Thailand. The sand flies were morphologically classified into eight species belonging to three genera (Sergentomyia, Phlebotomus and Idiophlebotomus). Sergentomyia iyengari was found at all collection sites and was the dominant species at most of these, followed in frequency by Sergentomyia barraudi and Phlebotomus stantoni, respectively. DNA barcodes generated from 68 sand flies allowed sorting into 14 distinct species with 25 operational taxonomic units, indicating a higher diversity (by 75%) than that based on morphological identification. Twelve barcoding sequences could not be assigned to any species for which cytochrome c oxidase subunit I sequences are available. All tested sand flies were negative for Leishmania DNA.ConclusionsOur results confirm the presence of several sand fly species in different provinces of Thailand, highlighting the importance of using DNA barcoding as a tool to study sand fly species diversity. While all female sand flies tested in this study were negative for Leishmania, the circulation of Leishmania spp. in the investigated areas cannot be ruled out.Graphical abstract
Highlights
Phlebotomine sand flies are vectors of Leishmania spp
Leishmaniasis is a neglected tropical disease caused by flagellate protists of the genus Leishmania, which are transmitted by the bite of infected female phlebotomine sand flies (Diptera: Psychodidae: Phlebotominae) [1]
Leishmaniasis is responsible for 20,000−30,000 deaths annually, and there are an estimated 1.3 million new cases each year, with 30,000 new cases of visceral leishmaniasis (VL) and more than a million new cases of cutaneous leishmaniasis (CL) [3]
Summary
Phlebotomine sand flies are vectors of Leishmania spp. At least 27 species of sand flies have been recorded in Thailand. Few studies have detected Leishmania infection in wild-caught sand flies, these studies were carried out only in those areas reporting human leishmaniasis cases. Leishmaniasis is a neglected tropical disease caused by flagellate protists of the genus Leishmania, which are transmitted by the bite of infected female phlebotomine sand flies (Diptera: Psychodidae: Phlebotominae) [1]. This vector-borne disease is endemic in Central and North America, the Indian subcontinent, the Mediterranean basin, the Middle East and Central Asia. Vector control is an important strategy for disease prevention, as it reduces and interrupts the transmission of this disease by reducing the density of sand fly populations [12]
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