Detection of an Unknown Trypanosoma DNA in a Phlebotomus stantoni (Diptera: Psychodidae) Collected From Southern Thailand and Records of New Sand Flies With Reinstatement of Sergentomyia hivernus Raynal & Gaschen, 1935 (Diptera: Psychodidae)

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.

First Report of Anuran Trypanosoma DNA in Flat-Tailed House Geckos (Reptilia: Gekkonidae) Collected from Southern Thailand: No Evidence as a Reservoir for Human Trypanosomatids

Over the years, cases of autochthonous leishmaniasis have been dramatically increasing in Thailand. Recently, several publications have claimed certain species of the phlebotomine sand flies and biting midges potentially serve as natural vectors of Leishmania and Trypanosoma species in this country. However, more information regarding the vector–parasite relationships, as well as their natural reservoirs in the country, still needs to be explored. Herein, we hypothesized that synanthropic reptiles in the leishmaniasis-affected area might be a natural reservoir for these parasites. In this present study, a total of nineteen flat-tailed house geckos were collected from the house of a leishmaniasis patient in Songkhla province, southern Thailand, and then dissected for their visceral organs for parasite detection. Small subunit ribosomal RNA (SSU rRNA) gene and internal transcribed spacer 1 (ITS-1)-specific amplifications were conducted to verify the presence of Trypanosoma and Leishmania parasites, respectively. Only Trypanosoma DNA was screened positive in eight gecko individuals by SSU rRNA-PCR in at least one visceral organ (4, 4, and 6 of the heart, liver, and spleen, respectively) and phylogenetically related to the anuran Trypanosoma spp. (An04/Frog1 clade) previously detected in three Asian sand fly species (Phlebotomus kazeruni, Sergentomyia indica, and Se. khawi). Hence, our data indicate the first detection of anuran Trypanosoma sp. in the flat-tailed house geckos from southern Thailand. Essentially, it can be inferred that there is no evidence for the flat-tailed house gecko (Hemidactylus platyurus) as a natural reservoir of human pathogenic trypanosomatids in the leishmaniasis-affected area of southern Thailand.

Phlebotomine Sand Flies in Southern Thailand: Entomological Survey, Identification of Blood Meals and Molecular Detection of Trypanosoma spp

Simple Summary

Phlebotomine sand flies (Diptera: Psychodidae) are hematophagous insects, and many species serve as vectors of various human and animal pathogens, including Leishmania and Trypanosoma protozoa. In Thailand, the first case of autochthonous leishmaniasis was reported 62 years ago. At present, the number of human cases is increasing in different regions of the country, but most cases are reported from southern Thailand. Therefore, we studied the potential transmission of Leishmania and Trypanosoma by sand flies in three provinces of southern Thailand, and analyzed blood sources of engorged sand fly females. We detected Trypanosoma sp. DNA in Sergentomyia barraudi, S. indica, S. khawi and Idiophlebotomus asperulus but no Leishmania spp. DNA. Moreover, bloodmeal analysis revealed that Trypanopsoma-positive females of S. barraudi and Sergentomyia sp. fed on dogs and humans, respectively. The results of this study contribute to the knowledge of leishmaniasis and trypanosomiasis presence and sand fly feeding behavior in southern Thailand.

Abstract

An entomological survey at rural and cavernicolous localities in four provinces in southern Thailand provided 155 blood-fed females of sand flies (Diptera: Psychodidae) that were identified based on morphological characters as Idiophlebotomus asperulus (n = 19), Phlebotomus stantoni (n = 4), P. argentipes (n = 3), Sergentomyia anodontis (n = 20), S. barraudi (n = 9), S. hamidi (n = 23), S. hodgsoni (n = 4), S. hodgsoni hodgsoni (n = 32), S. indica (n = 5), S. iyengari (n = 2), S. khawi (n = 17), S. silvatica (n = 11) and Sergentomyia sp. (n = 6). The dominant species in this study was S. hodgsoni hodgsoni, which was collected specifically in a Buddha cave. Screening for DNA of parasitic protozoans revealed eight specimens (5.16%) of four species (S. barraudi, S. indica, S. khawi and Id. asperulus) positive for Trypanosoma sp., while no Leishmania spp. DNA was detected. Blood meals of engorged females were identified by PCR-Restriction Fragment Length Polymorphism (PCR-RFLP) assay on a fragment of cytochrome b (cyt b) gene with a success rate 36%, humans, dogs, and rats being determined as sources of blood. Bloodmeal analysis of two Trypanopsoma-positive females (S. barraudi and Sergentomyia sp.) identified blood from dogs and humans, respectively. Our findings indicate that S. barraudi, S. indica, S. khawi and Id. asperulus may be incriminated in circulation of detected Trypanosoma spp.

Culicoides Latreille (Diptera: Ceratopogonidae) as potential vectors for Leishmania martiniquensis and Trypanosoma sp. in northern Thailand

Biting midges of genus Culicoides (Diptera: Ceratopogonidae) are the vectors of several pathogenic arboviruses and parasites of humans and animals. Several reports have suggested that biting midges might be a potential vector of Leishmania parasites. In this study, we screened for Leishmania and Trypanosoma DNA in biting midges collected from near the home of a leishmaniasis patient in Lamphun province, northern Thailand by using UV-CDC light traps. The identification of biting midge species was based on morphological characters and confirmed using the Cytochrome C oxidase subunit I (COI) gene. The detection of Leishmania and Trypanosoma DNA was performed by amplifying the internal transcribed spacer 1 (ITS1) and small subunit ribosomal RNA (SSU rRNA) genes, respectively. All the amplified PCR amplicons were cloned and sequenced. The collected 223 biting midges belonged to seven species (Culicoides mahasarakhamense, C. guttifer, C. innoxius, C. sumatrae, C. huffi, C. oxystoma, and C. palpifer). The dominant species found in this study was C. mahasarakhamense (47.53%). Leishmania martiniquensis DNA was detected in three samples of 106 specimens of C. mahasarakhamense tested indicating a field infection rate of 2.83%, which is comparable to reported rates in local phlebotomines. Moreover, we also detected Trypanosoma sp. DNA in one sample of C. huffi. To our knowledge, this is the first molecular detection of L. martiniquensis in C. mahasarakhamense as well as the first detection of avian Trypanosoma in C. huffi. Blood meal analysis of engorged specimens of C. mahasarakhamense, C. guttifer, and C. huffi revealed that all specimens had fed on avian, however, further studies of the host ranges of Culicoides are needed to gain a better insight of potential vectors of emerging leishmaniasis. Clarification of the vectors of these parasites is also important to provide tools to establish effective disease prevention and control programs in Thailand.

Culicoides are known to be vectors of several pathogens, including arboviruses and parasites. However, other investigations have demonstrated that Culicoides could be involved in the transmission of Leishmania and Trypanosoma parasites. Our studies demonstrated the first detection of L. martiniquensis in Culicoides mahasarakhamense and Trypanosoma sp., which is closely related to avian Trypanosome in C. huffi from an endemic area of leishmaniasis in northern Thailand. The finding of this work suggested that Culicoides biting midges are suspected to be the potential vector of L. martiniquensis and Trypanosoma parasites in Thailand.

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

BACKGROUND

The distribution of phlebotomine sand flies is changing rapidly due to climate change. This issue has implications for the epidemiology of sand fly-borne diseases, especially sand fly-associated viruses. Few studies concerning sand fly-associated viruses have been conducted in Thailand. Therefore, this study aimed to perform a molecular survey of groups of pathogenic RNA viruses belonging to the Orbivirus, Phlebovirus, and Flavivirus genera and family Rhabdoviridae in sand fly samples collected from southern Thailand.

METHODS

Sand flies were collected at two locations in Trang and Songkhla provinces of southern Thailand, and individual sand fly samples were processed for species identification and virus detection. The Orbivirus, Phlebovirus, and Flavivirus genera and family Rhabdoviridae molecular determination was performed by RT-PCR, and positive samples were identified by cloning and sequencing, cell culture inoculation, and phylogenetic analysis.

RESULTS

The results presented in this study were based on the analysis of a total of 331 female sand flies. This molecular study revealed evidence of Rhabdoviridae family virus presence in Phlebotomus papatasi (3/331, 0.9%). The findings demonstrated a new cluster of rhabdovirus that was closely related to Bactrocera dorsalis sigmavirus strain BDSV.abc5 and the lineages of insect-specific Rhabdoviridae. In addition, the Bayesian tree suggested that the common ancestor of this group was the dimarhabdovirus clade. It was assumed that the virus may have switched hosts during its evolution. However, the detection of Orbivirus, Phlebovirus, and Flavivirus genera using specific primers for RT-PCR was negative in the collected sand flies.

CONCLUSIONS

There is limited knowledge on the genetic diversity and ecology of Rhabdoviridae in Thailand. This is the first data regarding the circulation of Rhabdoviridae in Ph. papatasi from Thailand. We found a new cluster of rhabdoviruses that was close to the new B. dorsalis sigmavirus. It is possible that there is a great deal of diversity in this family yet to be discovered, and a more extensive survey for new rhabdoviruses may uncover viruses from a wide diversity of host taxa and broaden our understanding of the relationships among the Rhabdoviridae.

Sand fly identification and screening for Leishmania spp. in six provinces of Thailand

Background

Phlebotomine 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.

Methods

Species 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.

Results

A 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.

Conclusions

Our 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

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-04856-6.

Detection of Changuinola virus (Reoviridae: Orbivirus) in field-caught sand flies in southern Thailand

BACKGROUND

Phlebotomine sand flies are vectors for several pathogenic bacteria, parasites and viruses that have significant impacts on public health. Sand fly-associated viruses that cause diseases in humans and animals have recently received more attention. This study aimed to detect pathogenic viruses belonging to the Orbivirus genus, Phlebovirus genus, Flavivirus genus and family Rhabdoviridae in several field-caught sand fly species in southern Thailand.

METHODS

Sand flies were collected in southern Thailand using CDC light traps. Each sample was processed individually for virus screening using RT-PCR and sequencing.

RESULTS

Seven out of 60 sand fly samples (two samples of Idiophlebotomus spp., three of Phlebotomus papatasi and two of Sergentomyia khawi) were positive for the Orbivirus genus, which is closely related to Changuinola virus (CGLV). Phlebovirus genus, Flavivirus genus and family Rhabdoviridae were negative in all samples.

CONCLUSIONS

CGLV causes Changuinola virus disease or Changuinola fever, a febrile illness in Central and South America. The virus has never been reported in Thailand. This study is the first report of the detection of CGLV in sand flies from Thailand. An extensive study of sand flies from other regions of the country and the associations between sand flies, viruses and vertebrate hosts in Thailand should be undertaken.

Morphological identification keys for adults of sand flies (Diptera: Psychodidae) in Sri Lanka

Background

Phlebotomine sand flies are a medically important group of insects that is responsible for the transmission of leishmaniasis. Surveillance plays a major role in vector control programmes through exploring species abundance, potential entomological risk and designing appropriate control measures. In field surveillance programmes of such nature, morphological identification of vector species is of paramount importance. However, in Sri Lanka, there is no published taxonomic key available for the identification of leishmaniasis vectors.

Method

Identification keys for both male and females of the sand flies recorded in Sri Lanka were developed using morphological features. Main identification features were compared with the original observation of specimens collected from surveys and the use of published literature. Photographic illustrations of morphological features are included with the intention of making the keys user-friendly for non-taxonomists.

Results

A total of 22 sand fly species (Diptera: Psychodidae) of the genera Phlebotomus and Sergentomyia reported in Sri Lanka from 1910 to 2019 are included in the present work.

Conclusion

This simplified key, along with photographs taken from specimens would be beneficial to the health staff, entomologists and research staff who deal with leishmaniasis control programmes and vector-related studies.

Identification of trypanosomatids and blood feeding preferences of phlebotomine sand fly species common in Sicily, Southern Italy

In this study, the presence of Leishmania DNA and blood feeding sources in phlebotomine sand fly species commonly present in Sicily were investigated. A total of 1,866 female sand flies including 176 blood fed specimens were sampled over two seasons in five selected sites in Sicily (southern Italy). Sergentomyia minuta (n = 1,264) and Phlebotomus perniciousus (n = 594) were the most abundant species at all the sites, while three other species from the genus Phlebotomus (i.e., P. sergenti n = 4, P. perfiliewi n = 3 and P. neglectus n = 1) were only sporadically captured. Twenty-eight out of the 1,866 (1.5%) sand flies tested positive for Leishmania spp. Leishmania tarentolae DNA was identified in 26 specimens of S. minuta, while the DNA of Leishmania donovani complex was detected in a single specimen each of S. minuta and P. perniciosus. Interestingly, seven S. minuta specimens (0.4%) tested positive for reptilian Trypanosoma sp. Blood sources were successfully identified in 108 out of 176 blood fed females. Twenty-seven out of 82 blood sources identified in fed females of P. perniciosus were represented by blood of wild rabbit, S. minuta mainly fed on humans (16/25), while the sole P. sergenti fed specimen took a blood meal on rat. Other vertebrate hosts including horse, goat, pig, dog, chicken, cow, cat and donkey were recognized as blood sources for P. perniciosus and S. minuta, and, surprisingly, no reptilian blood was identified in blood-fed S. minuta specimens. Results of this study agree with the well-known role of P. perniciosus as vector of L. infantum in the western Mediterranean; also, vector feeding preferences herein described support the hypothesis on the involvement of lagomorphs as sylvatic reservoirs of Leishmania. The detection of L. donovani complex in S. minuta, together with the anthropophilic feeding-behaviour herein observed, warrants further research to clarify the capacity of this species in the transmission of pathogens to humans and other animals.

Detection of Leishmania and Trypanosoma DNA in Field-Caught Sand Flies from Endemic and Non-Endemic Areas of Leishmaniasis in Southern Thailand

Phlebotomine sand flies are tiny, hairy, blood-sucking nematoceran insects that feed on a wide range of hosts. They are known as a principal vector of parasites, responsible for human and animal leishmaniasis worldwide. In Thailand, human autochthonous leishmaniasis and trypanosomiasis have been reported. However, information on the vectors for Leishmania and Trypanosoma in the country is still limited. Therefore, this study aims to detect Leishmania and Trypanosoma DNA in field-caught sand flies from endemic areas (Songkhla and Phatthalung Provinces) and non-endemic area (Chumphon Province) of leishmaniasis. A total of 439 sand flies (220 females and 219 males) were collected. Head and genitalia dissection of female sandflies were done for morphology identification, and the remaining parts of those sand flies were then used for the detection of Leishmania and Trypanosoma parasites. The DNA was extracted from individual female sand flies. Polymerase chain reaction (PCR) anneal, specific to the ITS1 and SSU rRNA gene regions, was used to detect Leishmania and Trypanosoma DNA, respectively. The positive PCR products were cloned and sequenced. The results showed that the female sand fly species in this study consisted of Sergentomyia khawi (35.9%); Se. anodontis (23.6%); Phlebotomus betisi (18.6%); Ph. kiangsuensis (9.5%); Ph. asperulus (6.4%); Se. barraudi (2.3%); 0.9% of each Se. indica, Ph. stantoni, and Ph. major major; and 0.5% of each Se. sylvatica and Ph. mascomai. The PCR and sequence analysis were able to detect Leishmania and Trypanosoma DNA in sand fly samples, which were identified as L. martiniquensis, 1/220 (0.45%) in Se. khawi, 3/220 (1.36%) of T. noyesi in Se. anodontis, and Ph. asperulus. Fourteen (6.36%) of the unidentified trypanosome species in Se. khawi, Se. indica, Se. anodontis, Ph. asperulus, and Ph. betisi were found in all of the areas of this study. Interestingly, we found a 1/220 (0.45%) co-infection sample of L. martiniquensis and Trypanosoma in Se. khawi from Songkhla Province. These data indicate that several species of sand flies might be potential vectors of Leishmania and Trypanosoma parasites in southern Thailand. However, more extensive study for potential vectors using a larger number of sand flies should be conducted to prove whether these sand flies can be natural vectors of leishmaniasis and trypanosomiasis in both humans and animals. In addition, our study could be useful for the future study of infection prevention, including effective vector control for leishmaniasis and trypanosomiasis in Thailand.

Isolation of a Trypanosome Related to Trypanosoma theileri (Kinetoplastea: Trypanosomatidae) from Phlebotomus perfiliewi (Diptera: Psychodidae)

The Trypanosoma theileri group includes several trypanosome species hardly distinguishable due to the lack of discriminating morphological characters. Trypanosomes belonging to this group have been isolated from different bovine, ovine, and cervids in Europe, Africa, Asia, and Americas. The principal vectors of the T. theileri group are considered tabanid flies; however, T. melophagium is transmitted exclusively by sheep keds. In 2016, 128 sand flies out of 2,728 trapped in Valsamoggia municipality, Italy, were individually dissected and an unknown trypanosome strain, named TrPhp1, was isolated from a female of the sand fly Phlebotomus perfiliewi. Sequence analysis placed this trypanosome in the T. theileri group with very high homology to other trypanosomes detected in European cervids. This is the first report of the T. theileri group isolation from a sand fly, and the possible role of this insect group in the trypanosome transmission cycle is discussed. Within the T. theileri group, the phylogenetic analysis distinguished several lineages, which, unfortunately, do not correspond with their host specificity and their taxonomic status remains ambiguous.