Chronic generalized fibrotic skin lesions from disseminated leishmaniasis caused by Leishmania martiniquensis in two patients from northern Thailand infected with HIV

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.

An update on Leishmania martiniquensis infections: Transmission, clinical characteristics, and treatment

Leishmaniasis, caused by intracellular protozoa of the Leishmania genus, continues to be a global health issue, with approximately 700,000 to 1 million new cases occur annually worldwide. The disease is transmitted via the bite of infected female sand flies of the genus Phlebotomus, resulting in a range of symptoms known as cutaneous, mucocutaneous, and visceral leishmaniasis. The species Leishmania (Mundinia) martiniquensis, discovered in 1995, has been linked to cases in individuals with HIV, presenting with diverse clinical pictures. Interestingly, biting midges, not sandflies, has proved to serve as its potentially biological vector. This study focuses on understanding the transmission, clinical aspects, and effective treatment of L. martiniquensis infections. A comprehensive search strategy was employed to identify relevant published papers on the epidemiology, transmission, clinical characteristics, and treatment of L. martiniquensis up to August 2024. The clinical manifestations encompass localized cutaneous leishmaniasis, disseminated cutaneous leishmaniasis, mucocutaneous leishmaniasis, and visceral leishmaniasis. Leishmaniasis is associated with comorbidities such as inadequate nutrition, population displacement, and reduced immunity. Risk factors for Leishmania infection include the presence of domestic animals, age, gender, and environmental factors. Amphotericin B deoxycholate (AmB) is the main treatment. Combination therapy with allicin and andrographolide may reduce AmB side effects. Recent research investigates other treatments including 8-hydroxyquinoline, which works synergistically with AmB against L. martiniquensis.

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.

Nanopore-Based Surveillance of Leishmania Parasites in Culicoides Latrielle (Diptera: Ceratopogonidae) Caught from the Affected Community and Tham Phra Cave in Chiang Rai Province, the Endemic Area of Leishmaniasis in Northern Thailand

In this research, we elucidated the species composition of Culicoides biting midges, infection prevalence, and genetic diversity of Leishmania parasites circulating in the affected community in Chiang Rai Province, being the most endemic area in Northern Thailand. A total of 146 parous and gravid females, belonging to at least twelve Culicoides species in five subgenera and one species group, were trapped from three collection sites with an overall Leishmania prevalence of 26.7% (39/146). Leishmania was detected, using ITS1-PCR, in C. mahasarakamense (15), C. guttifer (11), C. (Trithecoides) spp. (8), C. jacobsoni (2), C. oxystoma (2), and C. orientalis (1). The evidence of Leishmania infection in these last five species represents new records in Northern Thailand. Given a high infection rate in cavernicolous specimens, this indicates an increased risk of parasite exposure when visiting the cave. Using the nanopore amplicon sequencing, L. martiniquensis was ubiquitously identified in all positives, and more than half of these were also co-infected with L. orientalis. The genetic diversity analysis revealed 13 and 17 unique haplotypes for L. martiniquensis and L. orientalis, respectively. Higher haplotype diversity and relatively low nucleotide diversity were observed in both parasite populations, suggesting recent population divergence. Neutrality tests (Tajima's D and Fu and Li's D) showed to be significantly negative, indicating rapid population growth or a selective sweep. Moreover, dominant haplotypes of both Leishmania species were 100% identical to those in all leishmaniasis patients previously reported from Northern Thailand, strongly supporting the imperative role of Culicoides spp. in disease transmission. Essentially, this research provides the first entomological surveillance data representing the sympatric existence, transmission dynamics, and genetic complexity of two autochthonous Leishmania (Mundinia) parasites in several Culicoides species in the endemic area of Northern Thailand. This would contribute to a more complete understanding of the epidemiology of vector infection and facilitate the development of vector control programs to effectively reduce the transmission of this neglected tropical disease in endemic areas of Northern Thailand.

In vitro susceptibility to miltefosine of amphotericin B-resistant Leishmania (Mundinia) martiniquensis

Leishmania (Mundinia) martiniquensis is a newly described species that causes human visceral, disseminated, and mucocutaneous leishmaniases. Amphotericin B deoxycholate (AmpB) is the first-line drug for the treatment of leishmaniasis in Thailand; however, several relapse cases of leishmaniasis caused by L. martiniquensis have been documented. In this study, in vitro susceptibility to AmpB and miltefosine (MIL) of wild-type (before treatment, LSCM1) and two AmpB-resistant L. martiniquensis strains (an in vitro-induced AmpB-resistant strain, AmpBRP2i, and a relapse strain, LSCM1-6) were determined. Results reveal that the IC50 value and resistance index against both drugs of promastigotes and intracellular amastigotes of the AmpBRP2i and LSCM1-6 strains were statistically significantly higher than those of the LSCM1 strain suggesting that cross-resistance with MIL occurred in both AmpB-resistant strains. The results of this study advocate further investigation into mechanisms that involve the complex nature of AmpB/MIL resistance in L. martiniquensis and development of effective methods for the identification of the AmpB-resistant parasites to help delivery of appropriate treatments for patients and for epidemiological surveys to survey the potential spread of drug-resistant strains.

Unusual Observations in Leishmaniasis-An Overview

Leishmaniasis significantly affects the population of the tropics and subtropics. Clinical features and infective species of Leishmania are the primary factors driving the direction of diagnosis. The rise in incidences of atypical presentations present a challenge in patient treatment. Knowledge of unusual/rare presentations can aid in having a broader perspective for including the different aspects during the examination and thus avoid misdiagnosis. A comprehensive literature survey was performed to present the array of atypical presentations confounding clinicians which have been seen in leishmaniasis. Case reports of unusual findings based on the localizations and morphology of lesions and infective species and the predominant geographical sites over almost five decades highlight such presentations in the population. Information regarding the clinical features recorded in the patient and the chosen treatment was extracted to put forward the preferred drug regimen in such cases. This comprehensive review presents various unusual observations seen in visceral leishmaniasis, post-kala-azar dermal leishmaniasis, cutaneous leishmaniasis, and mucocutaneous leishmaniasis. It highlights the need to consider such features in association with differential diagnosis to facilitate proper treatment of the patient.

DESCRIPTION, BIOLOGY, AND MEDICAL SIGNIFICANCE OF LEISHMANIA (MUNDINIA) CHANCEI N. SP. (KINETOPLASTEA: TRYPANOSOMATIDAE) FROM GHANA AND LEISHMANIA (MUNDINIA) PROCAVIENSIS N. SP. (KINETOPLASTEA: TRYPANOSOMATIDAE) FROM NAMIBIA

Genetic and phylogenetic analysis was performed on 2 isolates of Leishmania using DNA sequence data from the RNA polymerase II large subunit gene and the ribosomal protein L23a intergenic sequence. This showed the isolates to represent 2 new species within the subgenus Leishmania (Mundinia). The addition of Leishmania (Mundinia) chancei and Leishmania (Mundinia) procaviensis creates a total of 6 named species to date within this recently described subgenus of parasitic protozoa, containing both human pathogens and nonpathogens. Their widespread geographical distribution, basal phylogenetic position within the genus Leishmania, and probable non-sand fly vectors make these L. (Mundinia) species of significant medical and biological interest.

Amphotericin B resistance correlates with increased fitness in vitro and in vivo in Leishmania (Mundinia) martiniquensis

Amphotericin B (AmpB) deoxycholate is the available first-line drug used to treat visceral leishmaniasis caused by Leishmania (Mundinia) martiniquensis, however, some cases of AmpB treatment failure have been reported in Thailand. Resistance to drugs is known to affect parasite fitness with a potential impact on parasite transmission but still little is known about the effect of resistance to drugs on L. martiniquensis. Here we aimed to gain insight into the fitness changes occurring after treatment failure or in vitro-induced resistance to AmpB. L. martiniquensis parasites isolated from a patient before (LSCM1) and after relapse (LSCM1-6) were compared for in vitro and in vivo fitness changes together with an in vitro induced AmpB-resistant parasite generated from LSCM1 parasites (AmpBRP2i). Results revealed increased metacyclogenesis of the AmpBPR2i and LSCM1-6 strains (AmpB-resistant strains) compared to the LSCM1 strain and increased fitness with respect to growth and infectivity. The LSCM1-6 and AmpBRP2i strains were present in mice for longer periods compared to the LSCM1 strain, but no clinical signs of the disease were observed. These results suggest that the AmpB-resistant parasites could be more efficiently transmitted to humans and maintained in asymptomatic hosts longer than the susceptible strain. The asymptomatic hosts therefore may represent "reservoirs" for the resistant parasites enhancing transmission. The results in this study advocate an urgent need to search and monitor for AmpB-resistant L. martiniquensis in patients with relapsing leishmaniasis and in asymptomatic patients, especially, in HIV/Leishmania coinfected patients.

Leishmania spp. in indigenous populations: A mini-review

Leishmaniasis, considered a neglected vector-borne disease complex of global concern, has a significant impact on indigenous communities due to daily human and animal exposure in periurban, rural, and naturally preserved areas. This mini-review aims to assess and discuss studies of leishmaniasis in these communities of the New World and Old World, particularly those in the Americas and Asia. Such indigenous communities have been mostly built in poor traditional households with no mosquito-net protection, mostly located in environmentally protected areas, favoring vectors and reservoirs. The presence of leishmaniasis cases surrounding such indigenous areas indicated a high risk of infection, which may have been historically underestimated due to a lack of surveillance, even at present. The absence of studies of indigenous populations in recognized endemic areas may reflect insufficient health services. In conclusion, the persistence of this neglectful scenario may impact tragic outcomes and potential outbreaks in indigenous peoples and surroundings populations worldwide.

Case Report: Autochthonous Disseminated Cutaneous, Mucocutaneous, and Visceral Leishmaniasis Caused by Leishmania martiniquensis in a Patient with HIV/AIDS from Northern Thailand and Literature Review

Autochthonous leishmaniasis cases have been increasing continuously in Thailand over the years. We report multiple presentations of leishmaniasis in a 47-year-old patient with HIV/AIDS from Chiang Rai Province, northern Thailand. Physical examination showed multiple ulcerated papules, nodules, and plaques in a sporotrichoid distribution. Firm mucosal nodules on the hard palate and nasal opening, hepatosplenomegaly, and bilateral inguinal lymphadenopathy were found. Histopathological examination of the biopsies revealed an inflammatory infiltrate containing intramacrophage amastigotes compatible with Leishmania infection. In addition, Leishmania promastigotes were isolated successfully from the palatal biopsy and assigned the code MHOM/TH/2022/CULE6. Using internal transcribed spacer 1 polymerase chain reaction and sequence analysis, the causative parasite was identified as Leishmania martiniquensis. A definitive diagnosis of multiform leishmaniasis with disseminated cutaneous, mucocutaneous, and visceral involvement was established. The patient was administered intravenous amphotericin B 1 mg/kg/d for 2 weeks, followed by oral itraconazole 400 mg daily. At the 2-month follow-up, the cutaneous and mucosal lesions had improved significantly. To our knowledge, this is the first report of mucocutaneous involvement caused by L. martiniquensis in an immunocompromised patient with HIV/AIDS. In addition, we provide a literature review of leishmaniasis cases, reported formally in Thailand, resulting from this autochthonous parasite.

First Evidence of Co-Circulation of Emerging Leishmania martiniquensis, Leishmania orientalis, and Crithidia sp. in Culicoides Biting Midges (Diptera: Ceratopogonidae), the Putative Vectors for Autochthonous Transmission in Southern Thailand

Since 1996, autochthonous cases of emerging leishmaniasis caused by Leishmania (Mundinia) martiniquensis and Leishmania (Mundinia) orientalis have been more frequently reported, especially in the northern and southern parts of Thailand. However, the accurate identification of their natural vectors and reservoirs remains unconfirmed. Previous studies have suggested that these emerging parasites might be transmitted by other non-phlebotomine vectors. Herein, we speculated that Culicoides biting midges might act as the competent vectors responsible for autochthonous leishmaniasis in southern Thailand. In this research, 187 non-engorged, parous and gravid Culicoides females and 47 blood-engorged ones were trapped from the residences of two recently diagnosed visceral leishmaniasis patients in Sadao District and the unaffected site in Rattaphum District, Songkhla Province, southern Thailand. Species diversity and abundance of biting midges varied among the trapping sites. Using ITS1-PCR and BLASTn analysis, L. martiniquensis was predominantly detected in several Culicoides species, including C. peregrinus, C. oxystoma, C. mahasarakhamense, and C. huffi from the vicinity of patients’ houses; and in C. fordae and C. fulvus from the unaffected site. L. orientalis was also co-circulated in C. peregrinus and C. oxystoma caught near the second patient’s house. Additionally, Crithidia sp. were also detected using SSU rRNA-PCR across Culicoides spp. Host blood meal analysis of eight different Culicoides species from the unaffected site also revealed that all trapped Culicoides had fed on cows and goats, indicating the possible role of these mammalian species as reservoir hosts. Essentially, this study is the first entomological investigation, revealing the co-circulation of emerging trypanosomatids among several species of Culicoides biting midges and strongly supporting the potential role of this insect group as the main vectors responsible for the epidemiology of autochthonous leishmaniasis in southern Thailand.

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.

Genome Assembly and Genome Annotation of Leishmania martiniquensis Isolated from a Leishmaniasis Patient in Thailand

Leishmaniasis is a parasitic disease caused by Leishmania spp. with worldwide distribution. Autochthonous leishmaniasis has been reported to result from the infection by Leishmania martiniquensis in Thailand. This species was isolated in culture and subjected to high-throughput whole-genome sequencing. A total of 30.8 Mb in 36 chromosomes of the whole genome was assembled, annotated, and characterized. The L. martiniquensis under study was shown to segregate into the same clade and thus closely related to the previously identified L. martiniquensis (LU_Lmar_1.0), as determined by phylogenetic analysis of their genomic sequences along with those of representative kinetoplastid species. The total number of open reading frames genomewide predicts 8,209 protein-coding genes, of which 359 are putative virulence factors, including two previously known, e.g., cysteine proteinase C and superoxide dismutase B1. The results obtained from this study will be useful for further annotation and comparison with other Leishmania martiniquensis in the future.

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.

Anti-Leishmania activity of artesunate and combination effects with amphotericin B against Leishmania (Mundinia) martiniquensis in vitro

Leishmaniasis is an emerging disease in several countries over the world, especially in tropical regions. In Thailand, Leishmania (Mundinia) martiniquensis is the most frequent cause of visceral leishmaniasis and disseminated cutaneous leishmaniasis among HIV/AIDs patients. Amphotericin B (AmB) is the only drug currently available for the treatment of leishmaniasis in Thailand, but has some limitations like high renal toxicity and the prolonged hospitalization required for the treatment. Moreover, recurrence of the disease has been reported in several cases, indicating that new drugs or treatment strategies should be improved. In this study, Artesunate (ARS) was determined for anti-Leishmania activity against L. martiniquensis in promastigotes and amastigotes. In addition, the combination effects of ARS and AmB against intracellular amastigotes on THP-1 derived macrophages were also investigated for the first time. The result showed that L. martiniquensis was susceptible to ARS in both stages of the parasite. ARS was effective against intracellular amastigotes and safe to macrophage host cells, showing a SI value of 1,065. Furthermore, combination effects of ARS and AmB showed five synergistic combinations with a combination index (CI) value less than 1.0 (0.28-0.92) for intracellular amastigotes ranging from slight synergism to strong synergism. The strong synergistic combination had the highest dose reduction index (DRI), approximately a 9.7-fold reduction in AmB used. None of the treatments in combination had noticeable toxicity to THP-1 derived macrophages in the concentration range examined. The data provided in this study lead to further study in vivo and to develop a novel formulation of drug combinations to improve the outcome of leishmaniasis treatment.

Liver- and Spleen-Specific Immune Responses in Experimental Leishmania martiniquensis Infection in BALB/c Mice

Leishmania martiniquensis is a neglected cause of an emerging leishmaniasis in many countries, including France, Germany, Switzerland, the United States of America, Myanmar, and Thailand, with different clinical manifestations ranging from asymptomatic, cutaneous (CL), visceral (VL), and atypically disseminated CL and VL. The persistence of parasites and the recurrence of the disease after treatment are challenges in controlling the disease. To explore efficient prophylaxis and therapy, this study aimed to investigate infection outcome and organ-specific immune responses after inoculation with L. martiniquensis (MHOM/TH/2011/PG; 5 x 10⁶ promastigotes) in BALB/c mice via intravenous and intraperitoneal routes. A quantitative PCR technique, targeting L. martiniquensis ITS1, was primarily established to estimate the parasite burden. We found that the infection in the liver resolved; however, persistent infection was observed in the spleen. Histopathology with Leishmania-specific immunostaining revealed efficient hepatic granuloma formation, while splenic disorganization with parasitized macrophages at different locations was demonstrated. The mRNA expression of Th1 cytokines (IFN-γ, TNF-α, IL-12p40) and iNOS in the liver and spleen was upregulated. In addition, high expression of IL-10 was observed in the spleen in the chronic phase, revealing a significant moderate correlation with the parasite persistence [r₍₁₂₎ = 0.72, P = 0.009]. Further clarification of the mechanisms of persistent infection and experimental infection in immunosuppressed murine models are warranted.

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.

Molecular identification of two newly identified human pathogens causing leishmaniasis using PCR-based methods on the 3' untranslated region of the heat shock protein 70 (type I) gene

PCR-based methods to amplify the 3′ untranslated region (3′-UTR) of the heat shock protein 70 (type I) gene (HSP70-I) have previously been used for typing of Leishmania but not with Leishmania (Mundinia) martiniquensis and L. (Mundinia) orientalis, newly identified human pathogens. Here, the 3′-UTRs of HSP70-I of L. martiniquensis, L. orientalis, and 10 other species were sequenced and analyzed. PCR-Restriction Fragment Length Polymorphism (RFLP) analysis targeting the 3′-UTR of HSP70-I was developed. Also, the detection limit of HSP70-I-3′-UTR PCR methods was compared with two other commonly used targets: the 18S small subunit ribosomal RNA (SSU-rRNA) gene and the internal transcribed spacer 1 region of the rRNA (ITS1-rRNA) gene. Results showed that HSP70-I-3′-UTR PCR methods could be used to identify and differentiate between L. martiniquensis (480–2 bp) and L. orientalis (674 bp) and distinguished them from parasites of the subgenus Viannia and of the subgenus Leishmania. PCR-RFLP patterns of the 3′-UTR of HSP70-I fragments digested with BsuRI restriction enzyme successfully differentiated L. martiniquensis, L. orientalis, L. braziliensis, L. guyanensis = L. panamensis, L. mexicana = L. aethiopica = L. tropica, L. amazonensis, L. major, and L. donovani = L. infantum. For the detection limit, the HSP70-I-3′-UTR PCR method could detect the DNA of L. martiniquensis and L. orientalis at the same concentration, 1 pg/μL, at a similar level to the SSU-rRNA PCR. The PCR that amplified ITS1-rRNA was more sensitive (0.01 pg/μL) than that of the HSP70-I-3′-UTR PCR. However, the sizes of both SSU-rRNA and ITS1-rRNA PCR amplicons could not differentiate between L. martiniquensis and L. orientalis. This is the first report of using HSP70-I-3′-UTR PCR based methods to identify the parasites causing leishmaniasis in Thailand. Also, the BsuRI-PCR-RFLP method can be used for differentiating some species within other subgenera.

L. martiniquensis and L. orientalis, newly identified human pathogens, cause visceral leishmaniasis and cutaneous leishmaniasis in HIV-negative patients, respectively. However, both parasite species cause disseminated cutaneous leishmaniasis accompanying visceral leishmaniasis in HIV-positive patients. Species typing in leishmaniasis is important in diagnostics, epidemiology, and clinical studies. We show here that the 3′-UTR of HSP70-I region is a suitable target for PCR-based identification and discrimination between L. martiniquensis and L. orientalis. The technique is simple to perform and can be implemented in all settings where PCR is available. In species with similar PCR product size, the BsuRI-PCR-RFLP patterns of the 3′-UTR of HSP70-I fragments can be used for differentiating some species within other subgenera. However, where identification of species is essential or there is a travel history outside Thailand, sequencing of the HSP70-I-3′-UTR product or a similar discriminating target sequence is recommended. The PCR-based methods used in this study can also be applicable to the identification of Leishmania species obtained from vectors and reservoirs.

Field evaluation of four commercial light traps, trap placement, and effect of carbon dioxide on phlebotomine sand fly collection in northern Thailand

Several light trap devices have been invented and developed to assess the abundance of sand flies. Traps available in the market have different designs and attractant combinations to catch sand fly vectors. We evaluated the efficacy of four commercial light traps and determined the effect of trap placement and carbon dioxide (CO₂) on sand fly collection in northern Thailand. Trap evaluations were conducted at two natural caves located in Chiang Rai province, Thailand. In the first part of the study, the efficacies of four trap types including the Centers for Disease Control miniature light trap (CDC LT), Encephalitis Vector Survey trap (EVS), CDC Updraft Blacklight trap (CDC UB), and Laika trap (LK) were evaluated and compared using a Latin square experimental design. The second half of the study evaluated the influence of trap placement and CO₂ on sand fly collection. Additionally, CDC LT were placed inside, outside, and at the entrance of caves to compare the number of sand flies collected. For the trap efficacy experiment, a total of 11,876 phlebotomine sand flies were collected over 32 trap-nights. Results demonstrated that CDC LT, CDC UB, and LK collected significantly more sand flies than EVS (P > 0.05). However, there were no significant differences between the numbers of sand flies collected by CDC LT, CDC UB, and LK. A total of 6,698 sand flies were collected from the trap placement and CO₂ experiment over 72 trap-nights. Results showed that CO₂ did not influence the numbers of sand flies captured (P < 0.05), whereas trap placement at the entrance of the caves resulted in collection of significantly more sand flies than traps placed inside and outside of the caves. We found the CDC LT, CDC UB, and LK without CO₂ captured the greatest amount of sand flies. This was particularly observed when traps were placed at the entrance of a cave, perhaps because of the greater passage of stimuli caused by wind flow at the entrance of the cave. The light traps in this study can be used effectively to collect sand fly vectors in northern Thailand.

Lutzomyia longipalpis: an update on this sand fly vector

Lutzomyia longipalpis is the most important vector of Leishmania infantum, the etiological agent of visceral leishmaniasis (VL) in the New World. It is a permissive vector susceptible to infection with several Leishmania species. One of the advantages that favors the study of this sand fly is the possibility of colonization in the laboratory. For this reason, several researchers around the world use this species as a model for different subjects including biology, insecticides testing, host-parasite interaction, physiology, genetics, proteomics, molecular biology, and saliva among others. In 2003, we published our first review (Soares & Turco 2003) on this vector covering several aspects of Lu. longipalpis. This current review summarizes what has been published between 2003-2020. During this period, modern approaches were incorporated following the development of more advanced and sensitive techniques to assess this sand fly.

Experimental infection of Leishmania (Mundinia) martiniquensis in BALB/c mice and Syrian golden hamsters

Our objective was to investigate clinical progression, presence of parasites and DNAs, parasite loads, and histological alterations in BALB/c mice and Syrian golden hamsters after intraperitoneal inoculation with Leishmania (Mundinia) martiniquensis promastigotes with a goal to choosing an appropriate animal model for visceral leishmaniasis. Infections were monitored for 16 weeks. Infected BALB/c mice were asymptomatic during the infection course. Parasite DNAs were detected in the liver at week 8 of infection, followed by clearance in most animals at week 16; whereas in the spleen, parasite DNAs were detected until week 16. These results are correlated to those obtained measuring parasite loads in both organs. No parasite DNA and no alteration in the bone marrow were observed indicating that no dissemination occurred. These results suggest the control of visceralization of L. martiniquensis by BALB/c mice. In hamsters, weight loss, cachexia, and fatigue were observed after week 11. Leishmania martiniquensis parasites were observed in tissue smears of the liver, spleen, and bone marrow by week 16. Parasite loads correlated with those from the presence of parasites and DNAs in the examined tissues. Alterations in the liver with nuclear destruction and cytoplasmic degeneration of infected hepatocytes, presence of inflammatory infiltrates, necrosis of hepatocytes, and changes in splenic architecture and reduction and deformation of white pulp in the spleen were noted. These results indicate a chronic form of visceral leishmaniasis indicating that the hamster is a suitable animal model for the study of pathological features of chronic visceral leishmaniasis caused by L. martiniquensis.

Determination of anti-leishmanial drugs efficacy against Leishmania martiniquensis using a colorimetric assay

Autochthonous leishmaniasis caused by Leishmania martiniquensis cases in Thailand have dramatically increased in the recent years. L. martiniquensis infection primarily occurs in immunocompromised patients, especially AIDS patients. In Thailand, amphotericin B is the only drug available for leishmaniasis treatment, and some patients relapse after amphotericin B therapy. Moreover, the efficacy of anti-leishmanial drugs against L. martiniquensis has not been evaluated to date. In this study, we determined the efficacy of various anti-leishmanial drugs against the promastigote and intracellular amastigote stages of L. martiniquensis using a colorimetric assay. Two strains (CU1 and CU1R1) were isolated from leishmaniasis HIV co-infected patient from Songkhla province, southern Thailand. The CU1 strain was isolated from the patient in 2011, and CU1R1 was isolated from the same patient in 2013, when he was diagnosed as relapse leishmaniasis. The third strain (LSCM1) used in this study has been isolated from immunocompetent patient from Lamphun province, northern Thailand. All strains were identified as L. martiniquensis by sequencing of ribosomal RNA ITS-1 and large subunit of RNA polymerase II gene. Bioassays have been conducted both with promastigote and intracellular amastigote stages of the parasite. All L. martiniquensis strains have been tested against amphotericin B, miltefosine and pentamidine to determine the efficacy of the drugs against the parasite by using a PrestoBlue. The efficacy of miltefosine and pentamidine exhibit no significant difference between each stage of L. martiniquensis among all strains. Surprisingly, the promastigote and intracellular amastigote of the CU1R1 isolate, which was isolated from a relapsed patient after amphotericin B treatment, exhibited a two-fold increased inhibitory concentration (IC50) against amphotericin B compared with other strains, and the difference was statistically significant (p < 0.05). Moreover, intracellular amastigotes isolated from CU1R1 exhibited slightly increased susceptibility to amphotericin B compared with the promastigote (p < 0.05). The result of this experiment is a scientific evident to support that in case of relapsed leishmaniasis caused by L. martiniquensis, increasing dosage of amphotericin B is essential. Moreover, this study also determined efficacy of other anti-leishmanial drugs for treatment the leishmaniasis in Thailand in case of these drugs are available in the country and the clinicians should have alternative drugs for treatment leishmaniasis in Thailand apart from amphotericin B.

Antileishmanial Activity and Synergistic Effects of Amphotericin B Deoxycholate with Allicin and Andrographolide against Leishmania martiniquensis In Vitro

Leishmania (Mundinia) martiniquensis is a causative agent of visceral leishmaniasis, but in HIV-infected patients both visceral and disseminated cutaneous leishmaniasis are presented. Recurrence of the disease after treatment has been reported in some cases indicating that improved chemotherapy is required. In this study, the susceptibility of L. martiniquensis to Amphotericin B deoxycholate (AmB), allicin, and andrographolide was evaluated and the synergistic effects of allicin or andrographolide combined with AmB against L. martiniquensis intracellular amastigotes in mouse peritoneal exudate macrophages (PEMs) were investigated in vitro for the first time. The results showed that L. martiniquensis was highly susceptible to AmB as expected, but allicin and andrographolide had selectivity index (SI) values greater than 10, indicating promise in both compounds for treatment of host cells infected with L. martiniquensis. Four AmB/allicin combinations presented combination index (CI) values less than 1 (0.58–0.68) for intracellular amastigotes indicating synergistic effects. The combination with the highest dose reduction index (DRI) allowed an approximately four-fold reduction of AmB use in that combination. No synergistic effects were observed in AmB/andrographolide combinations. The data provided in this study leads for further study to develop novel therapeutic agents and improve the treatment outcome for leishmaniasis caused by this Leishmania species.

Development of Leishmania orientalis in the sand fly Lutzomyia longipalpis (Diptera: Psychodidae) and the biting midge Culicoides soronensis (Diptera: Ceratopogonidae)

Leishmania (Mundinia) orientalis is a newly described species causing human leishmaniasis in Thailand whose natural vector is unknown. L. orientalis infections in sand flies and/or biting midges under laboratory conditions have not been previously investigated. In this study, the development of L. orientalis in two experimental vectors, Lutzomyia longipalpis sand flies and Culicoides sonorensis biting midges was investigated for the first time using light microscopy, scanning electron microscopy, and histological examination. The results showed that L. orientalis was unable to establish infection in Lu. longipalpis. No parasites were found in the sand fly gut 4 days post-infected blood meal (PIBM). In contrast, the parasite successfully established infection in C. sonorensis. The parasites differentiated from amastigotes to procyclic promastigotes in the abdominal midgut (AMG) on day 1 PIBM. On day 2 PIBM, nectomonad promastigotes were observed in the AMG and migrated to the thoracic midgut (TMG). Leptomonad promastigotes appeared at the TMG on day 3 PIBM. Clusters of leptomonad promastigotes and metacyclic promastigotes colonized around the stomodeal valve with the accumulation of a promastigote secretory gel-like material from day 3 PIBM onwards. Haptomonad-like promastigotes were observed from day 5 PIBM, and the proportion of metacyclic promastigotes reached 23% on day 7 PIBM. The results suggest that biting midges or other sand fly genera or species might be vectors of L. orientalis.

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.

Leishmania (Mundinia) orientalis n. sp. (Trypanosomatidae), a parasite from Thailand responsible for localised cutaneous leishmaniasis

BACKGROUND

Leishmaniasis is an emerging disease in Thailand with an unknown incidence or prevalence. Although the number of properly characterized and clinically confirmed cases is about 20, it is suspected that this low number masks a potentially high prevalence, with clinical disease typically manifesting itself against an immunocompromised background, but with a substantial number of subclinical or cured cases of infection. To date leishmaniasis in Thailand has been mainly ascribed to two taxa within the recently erected subgenus Mundinia Shaw, Camargo & Teixeira, 2016, Leishmania (Mundinia) martiniquensis Desbois, Pratlong & Dedet, 2014 and a species that has not been formally described prior to this study.

RESULTS

A case of simple cutaneous leishmaniasis was diagnosed in a patient from Nan Province, Thailand. Molecular analysis of parasites derived from a biopsy sample revealed this to be a new species of Leishmania Ross, 1908, which has been named as Leishmania (Mundinia) orientalis Bates & Jariyapan n. sp. A formal description is provided, and this new taxon supercedes some isolates from the invalid taxon "Leishmania siamensis". A summary of all known cases of leishmaniasis with a corrected species identification is provided.

CONCLUSIONS

Three species of parasites are now known to cause leishmaniasis is Thailand, L. martiniquensis and L. orientalis n. sp. in the subgenus Mundinia, which contains the type-species Leishmania enriettii Muniz & Medina, 1948, and a single case of Leishmania infantum Nicolle, 1908. This study now enables epidemiological and other investigations into the biology of these unusual parasites to be conducted. It is recommended that the use of the taxonomically invalid name "L. siamensis" should be discontinued.

Comparison of LAMP and PCR for molecular mass screening of sand flies for Leishmania martiniquensis infection

BACKGROUND

Leishmaniasis caused by Leishmania martiniquensis infection has been reported in human and domestic animals of Martinique Island, Germany, Switzerland, USA, Myanmar and Thailand. The peculiar clinical features of disseminated cutaneous and visceral forms co-existence render the urgent need of specific diagnostic tool to identify the natural sand fly vectors for effective prevention and control strategies. Loop-mediated isothermal amplification (LAMP) of 18S rRNA gene as well as polymerase chain reaction (PCR) of minicircle kinetoplast DNA gene (PCR-mkDNA) have never been applied to detect L. martiniquensis and L. siamensis in sand fly vectors.

OBJECTIVE

The present study was aimed to validate malachite green-LAMP (MG-LAMP) and PCR-mkDNA techniques to detect L. martiniquensis in sand fly vectors, compared with the conventional PCR of internal transcribed spacer 1 (PCR-ITS1).

METHODS

We compared the validity of LAMP of 18S rRNA gene and PCR-mkDNA, to PCR-ITS1 in simulation model of L. martiniquensis infection in Sergentomyia gemmea sand flies. Attributable to the sensitivity and specificity, PCR-mkDNA was consecutively applied to detect L. martiniquensis in 380 female sand fly individuals captured in the newly identified affected region of Lamphun Province, Thailand.

FINDINGS AND MAIN CONCLUSIONS

Results showed that PCR-mkDNA could detect at least one promastigote per sand fly, which was 10-time superior to LAMP and PCR-ITS1. In addition, PCR-mkDNA was more specific, able to differentiate L. martiniquensis from other viscerotropic Leishmania species, such as L. siamensis, L. (L.) donovani, and L. (L.) infantum. Consecutively, mass screening of L. martiniquensis in 380 female sand fly individuals by PCR-mkDNA was implemented in a new affected area of Thailand where a patient with leishmaniasis/HIV co-infection resides; however Leishmania DNA was undetected. In conclusion, PCR-mkDNA is a promising tool for molecular mass screening of L. martiniquensis infection in outbreak areas where several species of Leishmania and sand flies co-exist.

Leishmaniasis in Thailand: A Review of Causative Agents and Situations

Before 1999, leishmaniasis was considered an imported disease in Thailand. Since then, autochthonous leishmaniasis was reported in both immmunocompetent and immmunocompromised patients especially in human immunodeficiency virus (HIV)/acquired immunodeficiency syndrome (AIDS). A new species was identified and named as Leishmania siamensis consisting of two lineages, that is, lineages TR and PG. Analysis of isoenzymes has clarified the more commonly detected L. siamensis lineage PG as Leishmania martiniquensis (MON-229), a species originally reported from the Martinique Island, whereas the L. siamensis lineage TR has been identified as the true novel species, L. siamensis (MON-324). Both cutaneous leishmaniasis (CL) and visceral leishmaniasis (VL) have been found among Thai patients. Disseminated CL and VL could be presented in some reported patients who had HIV/AIDS coinfection. So far, only sporadic cases have been reported; thus, the true prevalence of leishmaniasis should be determined in Thailand among the high-risk populations such as people with HIV/AIDS. A recent survey among animals identified L. martiniquensis DNA in black rats (Rattus rattus) suggesting a potential animal reservoir. In addition, L. martiniquensis DNA was identified in Sergentomyia gemmea and Sergentomyia barraudi, the predominant sandfly species in the affected areas. However, further studies are needed to prove that these sandflies could serve as the vector of leishmaniasis in Thailand.

Early detection of novel Leishmania species DNA in the saliva of two HIV-infected patients

BACKGROUND

Leishmaniasis caused by two new species of Leishmania; L. siamensis and L. martiniquensis have been recently described in Thailand. The disease has mainly been documented in AIDS patients from southern Thailand. In this study, polymerase chain reaction (PCR) was used to determine HIV-Leishmania co-infection in southern Thailand.

METHODS

One ml of saliva and 3 ml of EDTA blood were collected from HIV-infected patients for PCR detection of Leishmania DNA, cloning and sequencing. The positive PCR samples were then cultured on Schneider's insect medium.

RESULTS

Three out of 316 saliva samples collected from HIV-infected patients were found to be positive for Leishmania DNA (0.95%). Among the positive samples, one patient was observed with disseminated cutaneous lesions and also tested positive via saliva, whole blood and buffy coat in PCR. The second case presenting with nodular lesions also gave a positive saliva test via PCR two months prior to buffy coat. This diagnosis was confirmed by microscopic examination and a culture of biopsy samples from a nodule. The last case was an asymptomatic Leishmania infection which tested PCR positive only in saliva with a consecutive sample collection conducted for three months.

CONCLUSIONS

The prevalence of Leishmania infection in HIV infected patients within this study is 0.95%. Leishmania DNA was detected in saliva by PCR prior to blood and buffy coat of two HIV infected patients. Early detection of Leishmania DNA in saliva would be beneficial for the follow up of asymptomatic Leishmania infected patients, the early treatment of leishmaniasis and for surveillance survey purpose. However, full evaluation of sensitivity and specificity of this technique with a large cohort of patients is required before deployment.

Development of loop-mediated isothermal amplification (LAMP) for simple detection of Leishmania infection

Background

Leishmaniasis is a neglected tropical disease that is caused by an obligate intracellular protozoan of the genus Leishmania. Recently, an increasing number of autochthonous leishmaniasis cases caused by L. martiniquensis and the novel species L. siamensis have been described in Thailand, rendering an accurate diagnosis of this disease critical. However, only a few laboratories are capable of diagnosing leishmaniasis in Thailand. To expand leishmaniasis diagnostic capabilities, we developed a simple colorimetric loop-mediated isothermal amplification (LAMP) technique for the direct detection of Leishmania DNA.

Methods

LAMP was performed for 75 min using four primers targeting the conserved region of the18S ribosomal RNA gene, and the DNA indicator used was malachite green (MG). To simulate crude samples, cultured promastigotes of L. siamensis were mixed with blood or saliva. Also, clinical samples (blood, saliva, and tissue biopsies) were obtained from patients with cutaneous leishmaniasis (CL) and visceral leishmaniasis (VL). All samples were boiled for 10 min and introduced directly into the LAMP reaction mixture without DNA purification.

Results

The use of MG resulted in an unambiguous differentiation of positive and negative controls. For L. siamensis, the detection limit was 10³ parasites/mL or 2.5 parasites/tube. Saliva, tissue biopsies, and whole blood were indicative of active Leishmania infection, and their direct usages did not adversely affect the detection limit. In addition, this LAMP assay could detect DNA from multiple Leishmania species other than L. siamensis and L. martiniquensis, including L. aethiopica, L. braziliensis, L. donovani and L. tropica.

Conclusions

The simplicity and sensitivity of LAMP in detecting active Leishmania infection could enable the rapid diagnosis of leishmaniasis, thereby facilitating the survey and control of leishmaniasis in Thailand. However, our limited number of samples warranted a further validation with a larger cohort of patients before this assay could be deployed.

The Biting Midge Culicoides sonorensis (Diptera: Ceratopogonidae) Is Capable of Developing Late Stage Infections of Leishmania enriettii

Background

Despite their importance in animal and human health, the epidemiology of species of the Leishmania enriettii complex remains poorly understood, including the identity of their biological vectors. Biting midges of the genus Forcipomyia (Lasiohelea) have been implicated in the transmission of a member of the L. enriettii complex in Australia, but the far larger and more widespread genus Culicoides has not been investigated for the potential to include vectors to date.

Methodology/Principal Findings

Females from colonies of the midges Culicoides nubeculosus Meigen and C. sonorensis Wirth & Jones and the sand fly Lutzomyia longipalpis Lutz & Nevia (Diptera: Psychodidae) were experimentally infected with two different species of Leishmania, originating from Australia (Leishmania sp. AM-2004) and Brazil (Leishmania enriettii). In addition, the infectivity of L. enriettii infections generated in guinea pigs and golden hamsters for Lu. longipalpis and C. sonorensis was tested by xenodiagnosis. Development of L. enriettii in Lu. longipalpis was relatively poor compared to other Leishmania species in this permissive vector. Culicoides nubeculosus was not susceptible to infection by parasites from the L. enriettii complex. In contrast, C. sonorensis developed late stage infections with colonization of the thoracic midgut and the stomodeal valve. In hamsters, experimental infection with L. enriettii led only to mild symptoms, while in guinea pigs L. enriettii grew aggressively, producing large, ulcerated, tumour-like lesions. A high proportion of C. sonorensis (up to 80%) feeding on the ears and nose of these guinea pigs became infected.

Conclusions/Significance

We demonstrate that L. enriettii can develop late stage infections in the biting midge Culicoides sonorensis. This midge was found to be susceptible to L. enriettii to a similar degree as Lutzomyia longipalpis, the vector of Leishmania infantum in South America. Our results support the hypothesis that some biting midges could be natural vectors of the L. enriettii complex because of their vector competence, although not Culicoides sonorensis itself, which is not sympatric, and midges should be assessed in the field while searching for vectors of related Leishmania species including L. martiniquensis and "L. siamensis".

This study investigates the laboratory infection of two species of Culicoides biting midges (Diptera: Ceratopogonidae) and one species of sand fly (Diptera: Psychodidae) with two species of Leishmania. These members of the L. enriettii complex were demonstrated to colonize the stomodeal valve of Culicoides sonorensis following membrane feeding on blood-parasite mixtures or direct feeding on guinea pigs that demonstrated clinical signs of infection. In contrast, three other species of Leishmania that are known to be transmitted by sand flies failed to successfully develop in C. sonorensis. A sand fly species which is highly permissive to Leishmania infection, Lu. longipalpis, a widespread vector of L. infantum in Latin America, was found to support only moderate infections of L. enriettii from Brazil and Leishmania sp. AM-2004 from Australia. In addition to establishing a suitable laboratory model for infection of Culicoides with L. enriettii, successful infection of C. sonorensis highlights that vectors other than sand flies should be considered as part of epidemiological studies on parasites belonging to the L. enriettii complex.