A new cluster of rhabdovirus detected in field-caught sand flies (Diptera: Psychodidae: Phlebotominae) collected from southern Thailand

Viral metagenomics of hematophagous insects collected in the Carajas mining complex, Pará State, Brazil

Hematophagous insects are vectors of viruses that cause diseases in humans and animals worldwide. Mosquitoes (Culicidae), biting midges (Ceratopogonidae), and sandflies (Psychodidae) were collected in three municipalities (Marabá, Canaã dos Carajás, and Curionópolis) in the state of Pará, Brazil, in 2019. Morphological keys were used for the taxonomic identification of insect species. High-throughput sequencing and metagenomic analysis were employed to characterize the viromes of the hematophagous insects. We characterized the virome of 839 insects grouped into 14 pools. A total of 729 million paired reads were generated, with 12 million viral sequences (3 % of the reads). The families Reoviridae, Myoviridae, Retroviridae, and Poxviridae were found in all samples of this study. Phylogenies of RNA-dependent RNA polymerase (RdRp) from viruses of the families Chuviridae, Dicistroviridae, Flaviviridae, Iflaviridae, Mesoniviridae, Phenuiviridae, and Rhabdoviridae were performed. In this study, the first isolation of the Guaico Culex Virus (GCXV) in the northern region of Brazil was obtained from a pool of Culex (Melanoconion) spp. mosquitoes collected in Curionópolis. The data obtained in this study demonstrate that the Carajás region has an ecosystem rich in viruses. Additional studies are needed to understand the dynamics of viruses in vectors, vertebrates, and the human population in the region.

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.

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.

Significance of eggshell morphology as an additional tool to distinguish species of sand flies (Diptera: Psychodidae: Phlebotominae)

Morphological characteristics of eggshells are important in sand fly ootaxonomy. In this study, eggshells from Phlebotomus stantoni Newstead, Sergentomyia khawi (Raynal), and Grassomyia indica (Theodor) sand flies collected in Chiang Mai province, Thailand were examined and characterized using light microscopy (LM) and scanning electron microscopy (SEM). Then, eggshell morphology of these three species was described for the first time. Each gravid female was forced to lay eggs by decapitation and the eggs were collected for SEM analysis. Egg laying females were identified by morphological examination and molecular typing using cytochrome b (Cytb) as a molecular marker. The chorionic sculpturing of Ph. stantoni eggs combines two patterns on the same egg: unconnected parallel ridges and reticular patterns. Sergentomyia khawi and Gr. indica have similar chorionic polygonal patterns, but their exochorionic morphology and aeropylar area are different. Results indicate that eggshell morphological characteristics such as chorionic pattern, exochorionic morphology, inter-ridge/boundary area, aeropylar area (including the number of aeropyles) and basal layer, can be useful to develop morphological identification keys of eggs. These can serve as an additional tool to distinguish species of sand flies. In addition, the chorionic sculpturing of the eggs of the three species of sand flies observed by LM is useful for species identification in gravid females with spermathecae obscured by eggs.