Taxonomical insights and ecology of sandfly (Diptera, Psychodidae) species in six provinces of Northern Vietnam

An integrative taxonomic approach reveals two putatively novel species of phlebotomine sand fly (Diptera: Psychodidae) in Thailand

BACKGROUND

The subfamily Phlebotominae comprises 1028 species of sand fly, of which only 90 are recognized as vectors of pathogenic agents such as Trypanosoma, Leishmania, and Bartonella. In Thailand, leishmaniasis-a sand fly-borne disease-is currently endemic, with 36 documented sand fly species. However, many cryptic species likely remain unidentified. To improve our understanding of the distribution, habitat preferences, and role in disease transmission of these sand flies, further research is necessary.

METHODS

Sand flies were collected using CDC light traps from 13 locations across four provinces in Thailand between October 2022 and October 2023. Initially, species identification was based on morphological characteristics, employing identification keys, and subsequently confirmed through mitochondrial cytochrome oxidase c subunit I (COI) and cytochrome b (Cytb) sequencing. Species identities were verified using BLASTN and BOLD searches. Species delimitation was conducted using Automatic Barcode Gap Discovery (ABGD) and Assemble Species by Automatic Partitioning (ASAP) with three substitution models. Additionally, intraspecific and interspecific genetic variation, neutrality tests (including Tajima's and Fu and Li's D* tests), phylogenetic analyses, and TCS haplotype network analysis were performed using the obtained sequences.

RESULTS

A total of 3693 phlebotomine sand flies were collected, with 2261 (61.22%) identified as female. Integrative analyses combining morphological data, BLASTN searches, phylogenetic assessments, and species delimitation confirmed the identification of four genera: Sergentomyia, Grassomyia, Phlebotomus, and Idiophlebotomus, encompassing 12 species: Sergentomyia anodontis, Se. sylvatica, Se. perturbans, Se. barraudi, Se. hivernus, Se. khawi, Se. siamensis, Grassomyia indica, Phlebotomus barguesae, Ph. stantoni, Idiophlebotomus asperulus, and Id. longiforceps. Furthermore, molecular analysis revealed cryptic and complex species, including two putatively novel species, Se. sp. 1 and Se. sp. 2, as well as a unique haplotype.

CONCLUSIONS

This study, which integrated genetic and morphological identification techniques, identified 12 sand fly species and unveiled cryptic and complex species, including two putatively novel species (Se. sp. 1 and Se. sp. 2) and a unique haplotype. The findings underscore the utility of mitochondrial genes, combined with species delimitation methodologies, as reliable approaches for identifying diverse sand fly species.

Cave-dwelling phlebotomine sand flies (Diptera: Psychodidae: Phlebotominae) in Thailand: population composition and pathogen detection of Bartonella and Trypanosoma

BACKGROUND

Leishmaniasis is an emerging vector-borne disease that occurs in Thailand. Although Leishmania (Mundinia) parasites, the causative agents of the disease have been identified, the vectors of the disease remain unidentified. In the present study, we collected sand flies from three caves located in endemic areas of leishmaniasis, including Lampang and Chiang Rai in northern Thailand, and Songkhla in southern Thailand.

METHODS

Female sand flies were identified on the basis of morphological characteristics and confirmed by cytochrome c oxidase subunit I (COI) sequencing. Sand fly DNA samples were screened for Leishmania, Trypanosoma, and Bartonella DNA by polymerase chain reaction (PCR) on the basis of the ITS1 region of the ribosomal RNA (rRNA), SSU rRNA, and gltA genes, followed by phylogenetic relationships and haplotype diversity analysis.

RESULTS

A total of 557 sand flies were identified, comprising four genera (Sergentomyia, Phlebotomus, Grassomyia, and Idiophlebotomus) and 11 species. Molecular detection of pathogens demonstrated that Leishmania DNA was not detected. However, Trypanosoma DNA was detected in 11 samples of Phlebotomus mascomai from Lampang (7 for T. noyesi), Se. anodontis from Chiang Rai (1 each for T. noyesi and Trypanosoma sp.), and Se. khawi from Songkhla (2 for Trypanosoma sp.). Bartonella DNA was detected in 16 samples of Se. anodontis and Se. barraudi s.l. from Chiang Rai, Se. anodontis from Lampang, and Se. khawi from Songkhla. The novel Bartonella sp. detected in Thai sand flies was phylogenetically related to Bartonella sp. from bats. Genetic diversity analysis showed high haplotype diversity in both Trypanosoma parasites and Bartonella bacteria.

CONCLUSIONS

The data from the present study indicate that phlebotomine sand flies could be potential vectors of zoonotic diseases caused by Trypanosoma sp. and Bartonella sp. To our knowledge, this is the first report of the natural infection of Bartonella associated with bats in Thailand, and the presence of T. noyesi and amphibian trypanosomes. However, further investigation is required to elucidate and enhance the understanding of potential vectors and transmission dynamics of pathogens in Thailand, particularly with regard to different seasonality, habitats, and host ranges.

Survey of sand fly fauna in six provinces of Southern Vietnam with species identification using DNA barcoding

BACKGROUND

Sand flies, belonging to the Psychodidae family, represent small, hairy insects that serve as significant 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 flies. To address this, the current study aimed to survey sand fly biodiversity.

METHODS

Sand flies from six provinces in Southern Vietnam were collected using CDC light traps. Sand flies were subsequently identified morphologically and confirmed molecularly using mitochondrial cytochrome oxidase c subunit I (COI) and cytochrome b (cytb) sequences. BLASTN searches were conducted, and the species identity of sand flies was further confirmed through a Barcode of Life Database (BOLD) search utilizing COI sequences. Subsequently, nucleotide sequences were subjected to a panel of analyses including intraspecific variation, phylogenetic relationships and haplotype network. The average densities of collected sand flies (sand flies/trap/night) and species richness were also recorded.

RESULTS

A total of 753 sand flies were collected. After excluding damaged specimens, six sand fly species, namely Phlebotomus stantoni, Sergentomyia khawi, Se. silvatica, Se. barraudi, Se. bailyi and Grassomyia indica, were identified. All conspecific sand fly 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 identification, BLASTN analysis and BOLD search. For intraspecific variation of sand flies obtained from the current study, COI diversity indices were consistently higher than those of cytb.

CONCLUSIONS

This study provides the first updates on morphological and molecular characterization of sand flies in Southern Vietnam. This acquired knowledge on sand fly species composition is essential for controlling sand fly-borne diseases in this potentially endemic region.

Novel duplex TaqMan-based quantitative PCR for rapid and accurate diagnosis of Leishmania (Mundinia) martiniquensis and Leishmania (Mundinia) orientalis, responsible for autochthonous leishmaniasis in Thailand

The World Health Organization has recently declared Thailand a leishmaniasis hotspot in Southeast Asia due to the continuous increase in new symptomatic and asymptomatic cases over the years. This emerging parasitic disease is known to be caused by two autochthonous species of Leishmania belonging to the newly described subgenus Mundinia, namely L. martiniquensis and L. orientalis. In Thailand, clinical cases due to L. martiniquensis typically present with visceral leishmaniasis, whereas L. orientalis mainly causes localized cutaneous leishmaniasis. Although Leishmania species confirmation is essential for clinical diagnosis and treatment planning, the availability of highly accurate and rapid diagnostic methods remains limited. In this study, we developed a duplex TaqMan quantitative PCR assay using newly designed species-specific primers and probes based on sequences from the nucleotide and genome databases of Leishmania spp. retrieved from GenBank. The duplex qPCR assay was optimized to specifically amplify the internal transcribed spacer 1 (ITS1) of L. martiniquensis and the heat shock protein 70 (type I) intergenic region (HSP70-I IR) of L. orientalis with high amplification efficiencies. The performance of the optimized duplex qPCR was evaluated by analyzing 46 DNA samples obtained from cultures, and clinical and insect specimens, consistent with the results of the previously validated 18S rRNA-qPCR and ITS1-PCR. The duplex qPCR could detect both species of Leishmania at a limit of detection of one copy per reaction and did not cross-amplify with other pathogen DNA samples. Standard curves of the singleplex and duplex assays showed good linearity with excellent amplification efficiency. Using conventional ITS1-PCR and plasmid sequencing as a reference standard assay, the duplex qPCR showed diagnostic sensitivity and specificity of 100% and positive and negative predictive values of 100% for both Leishmania species with a perfect level of agreement (kappa = 1.0). The novel duplex TaqMan-based qPCR has shown to be a rapid, cost-effective, and highly accurate diagnostic tool for the simultaneous detection and identification of two autochthonous Leishmania spp. in a variety of clinical and entomological samples. This will greatly facilitate early diagnosis, treatment monitoring, and surveillance, especially in leishmaniasis-endemic areas where sequencing-based diagnosis is not routinely available.

A study on the diversity of phlebotomine sand flies (Diptera, Psychodidae) in karstic limestone areas in Vientiane Province, Laos, with a description of two new species of Sergentomyia França and & Parrot

BACKGROUND

Southeast Asia is well known as a hotspot of biodiversity. However, very little is known about cave-dwelling hematophagous insects that are medically important. Taxonomic knowledge and ecology of phlebotomine sand flies are very poorly studied in Laos, as well as in other countries in the region. Herein, we report species diversity data and some notes on the ecology of the detected species from these karstic limestone areas of Laos.

METHODS

Phlebotomine sand flies were collected using Centers for Disease Control and Prevention (CDC) light traps from limestone cave locations in three districts of Vientiane Province, Laos. Both morphological and molecular techniques were used for sand fly identification. Species diversity and abundance were analyzed according to sites, locations, collection seasons, and trapping positions.

RESULTS

A total of 6564 sand flies, of which 5038 were females and 1526 were males, were morphologically identified into 20 species belonging to five genera (Chinius, Idiophlebotomus, Phlebotomus, Sergentomyia, and Grassomyia). The most abundant species were Chinius eunicegalatiae, Phlebotomus stantoni, Sergentomyia hivernus, Se. siamensis, and Idiophlebotomus longiforceps. Cytochrome b analysis results supported the morphological identification and revealed that Se. siamensis was separated from other members of the Se. barraudi group. Two new species, Se. dvoraki n. sp. and Se. marolii n. sp., were described. Sand fly density was generally high except in a cave in Vangvieng, with species richness ranging from 14 to 18 across different caves. Outside caves had higher species richness (R = 20) and diversity (H = 2.50) than cave entrances (R = 18, H = 2.41) and interiors (R = 16, H = 2.13). Seasonal variations showed high sand fly density in Feung and Hinheup during both dry and rainy seasons, while Vangvieng had a notable decrease in density during the dry season (D = 6.29).

CONCLUSIONS

This study revealed that the diversity of phlebotomine sand fly fauna in Laos, particularly in karstic limestone areas, is greater than previously known. However, the taxonomic status of many species in Laos, as well as Southeast Asia, still needs more in-depth study using both morphological characters and molecular methods. Many species could be found from inside, at the entrance, and outside of caves, indicating a wide range of host-seeking behavior or possible natural breeding in the karstic cave areas.

Sergentomyia khawi: a potential vector for Leishmania and Trypanosoma parasites affecting humans and animals and insecticide resistance status in endemic areas of Songkhla, southern Thailand

BACKGROUND

Sand flies serve as crucial vectors in various medical and veterinary diseases. Sand fly-borne diseases pose a significant public health burden globally, as the causative agents can infect a diverse range of hosts, leading to severe consequences such as leishmaniasis and sand fly fever. Additionally, the widespread use of insecticides for agricultural purposes and mosquito control is not specifically targeted at sand flies, potentially leading to resistance development. We investigated sand fly species, their potential role as vectors of various parasitic agents, and insecticide resistance in the endemic regions of Natawi and Sadao districts in Songkhla, Thailand.

METHODS

Sand flies were collected using CDC light traps. The collected sand flies were then identified to species level using molecular techniques. Subsequent analyses included the detection of pathogens and the identification of pyrethroid resistance mutations within the voltage-sensitive sodium channel (Vgsc) domain IIS6 gene, followed by sequence analysis.

RESULTS

The study identified nine sand fly species belonging to the genera Phlebotomus and Sergentomyia. The DNA of Sergentomyia khawi was the only species found to test positive for one sample of Leishmania orientalis in Sadao district. This finding represents the first detection of L. orientalis in Thailand. Moreover, three samples of Leishmania martiniquensis and four samples of Trypanosoma sp. were found in the Natawi district. No I1011M, L1014F/S, V1016G, or F1020S mutations were detected in Vgsc gene.

CONCLUSIONS

The results of this study provide valuable information on sand fly species and the continuous circulation of Leishmania spp. and Trypanosoma spp. in Songkhla, southern Thailand. Moreover, the development of geo-spatial information on vectors, parasites, and insecticide resistance in sand flies has the potential to provide well-informed risk assessments and evidence-based guidance for targeted vector control in Thailand. These results can serve as a foundation for integrating the One Health approach, which is crucial for disease control, considering the diverse ecological interactions among human and/or animal reservoir hosts, parasites, and sand fly vectors.

Phlebotomine sand flies (Diptera, Psychodidae) from Pha Tong cave, Northern Thailand with a description of two new species and taxonomical thoughts about Phlebotomus stantoni

BACKGROUND

In South-East Asia, Thailand is the country with the highest number of human autochthonous cases of leishmaniases mostly due to Leishmania martiniquensis. Their transmission remains unresolved to date even though sand flies are known vectors of leishmaniases. As such, we focused a study on the sand fly fauna of a cave in Thailand to explore the biodiversity of potential Leishmania vectors.

MAIN RESULTS

We carried out an inventory in Pha Tong cave. We caught and identified 570 Phlebotomine sand flies (452 females and 118 males) and identified 14 species belonging to the genera Phlebotomus, Idiophlebotomus, Chinius, Sergentomyia and Grassomyia. Among these 14 species, two could not be related to known sand fly species. Herein, we propose the description of two new sand fly species, previously unknown to science. The first new species, Phlebotomus shadenae n. sp. is a sand fly of the subgenus Anaphlebotomus. It is morphologically close to Ph. stantoni, a species widely distributed throughout Southeast Asia. However, it differs by the length of the genital filaments in males or by the length of the ducts of the spermathecae in females as well as the high divergence of cytochrome b sequences. Additionally, we revised the systematics of the subgenus Anaphlebotomus and reinstated, by examination of its holotype, the validity of Ph. maynei, an Indian wrongly considered as a synonym of Ph. stantoni in the past. The second new species, Sergentomyia maiae n. sp., differs from a species in the same group, Se. barraudi, by an original cibarial double row of vertical teeth as well as by molecular data.

CONCLUSIONS

We propose the description of two new sand fly species for Science with morphological and molecular evidence. Ph. shadenae n. sp. was also found to be distributed in the south of Thailand and in Laos. Future studies need to determine whether these two species can play a role as vectors of Leishmania parasites, Trypanosomatids or Phlebovirus. Most of the species caught in the present study are strictly cavernicolous except Grassomyia sp. and a few Sergentomyia.

Phlebotomine sand flies (Diptera: Psychodidae) and sand fly-borne pathogens in the Greater Mekong Subregion: a systematic review

Phlebotomine sand flies are proven or suspected vectors of several pathogens of importance, including leishmaniasis, bartonellosis and sand fly fevers. Although sand flies have a worldwide distribution, there has been limited research published on sand flies and sand fly-borne pathogens throughout the Greater Mekong Sub-region (GMS). This review followed the PRISMA guidelines to determine the biodiversity and presence of phlebotomine sand flies and their associated pathogens in the GMS, specifically Cambodia, Thailand, the Lao People's Democratic Republic (Laos), Malaysia and Vietnam. A total of 1472 records were identified by searching electronic databases, scanning reference lists of articles and consulting experts in the field. After screening of title and abstracts, 178 records remained and were further screened for original data (n = 34), not having regional data (n = 14), duplication of data (n = 4), records not available (n = 4) and no language translation available (n = 2). A total of 120 studies were then included for full review, with 41 studies on sand fly-related disease in humans, 33 studies on sand fly-related disease in animals and 54 entomological studies focused on sand flies (5 papers contained data on > 1 category), with a majority of the overall data from Thailand. There were relatively few studies on each country, with the exception of Thailand, and the studies applied different methods to investigate sand flies and sand fly-borne diseases, impacting the ability to conduct meaningful meta-analysis. The findings suggest that leishmaniasis in humans and the presence of sand fly vectors have been reported across several GMS countries over the past 100 years, with local transmission in humans confirmed in Thailand and Vietnam. Additionally, local Mundinia species are likely transmitted by biting midges. Findings from this study provide a framework for future investigations to determine the geographic distribution and risk profiles of leishmaniasis and other associated sand fly-borne disease throughout the GMS. It is recommended that researchers expand surveillance efforts across the GMS, with an emphasis placed on entomological surveys, syndromic and asymptomatic monitoring in both humans and animals and molecular characterization of sand flies and sand fly-borne pathogens, particularly in the understudied countries of Cambodia, Vietnam and Laos.

Case Report: The First Case Report of Visceral Leishmaniasis in Cambodia

Leishmaniasis is considered a neglected tropical disease that is commonly found in Asia, Africa, South America, and Mediterranean countries. Visceral leishmaniasis (VL) is the most severe form of the disease and is almost universally fatal if left untreated. The symptoms of VL overlap with many infectious diseases, malignancies, and other blood disorders. The most common findings include fever, cytopenias, and splenomegaly. Given the nonspecific symptoms, the diagnosis requires detailed laboratory investigations, including bone marrow examination, that can be challenging in low- and middle-income countries. Diagnostic limitations likely lead to the underdiagnosis or delay in diagnosis of VL. We describe, to our knowledge, the first case report of VL in Cambodia in a child presenting with fever, anemia, and thrombocytopenia. The diagnosis required a liver biopsy and multiple bone marrow biopsies to visualize intracellular Leishmania spp. Our case illustrates the diagnostic challenges and the importance of timely diagnosis. This case also highlights the need for heightened awareness of the diagnostic findings of VL and improved reporting of tropical diseases.