Prevalence and risk factors associated with Leishmania infection in Trang Province, southern Thailand

Asymptomatic Leishmania Infection among Blood Donors in a Southern Province of Thailand

Leishmaniasis poses significant public health challenges in endemic regions. Understanding the prevalence of asymptomatic Leishmania infection and identifying risk factors among blood donors is crucial. This study addressed a knowledge gap by evaluating the prevalence of asymptomatic Leishmania infection and pinpointing associated risk factors among blood donors in an endemic area in Thailand and aimed to enhance blood donation safety protocols and reduce the risk of transfusion-transmitted Leishmania infection. A cross-sectional study and a longitudinal follow-up were conducted among 500 blood donors in Trang Province, southern Thailand. A serological test was performed using the direct agglutination test (DAT), and DNA detection was performed using nested polymerase chain reaction (nPCR) to screen for Leishmania infection. Potential risk factors associated with the infection were also assessed. The study identified a 19.0% prevalence of asymptomatic Leishmania infection among blood donors, with nPCR proving more effective in detecting infections (13.0%) than DAT (6.4%). Notably, Leishmania martiniquensis was the predominant species identified, highlighting the local epidemiological profile of Leishmania infection. Furthermore, using multivariate analysis, living in stilt houses was independently associated with Leishmania infection (adjusted odds ratio = 1.85; 95% CI = 1.04-3.28; P = 0.035). A high prevalence of asymptomatic Leishmania infection among blood donors underscores the need for integrating comprehensive Leishmania screening protocols into blood donation processes, particularly in endemic regions. It advocates for using molecular diagnostics to enhance detection accuracy. Furthermore, living in stilt houses as a risk factor emphasizes the importance of environmental management in leishmaniasis control efforts.

Incidence and persistence of asymptomatic Leishmania infection among HIV-infected patients in Trang province, Southern Thailand: A cohort study

Leishmaniasis poses a significant health burden, particularly among immunocompromised patients. In Thailand, Leishmania infection caused by Leishmania martiniquensis and Leishmania orientalis lacks information about the incidence and risk factors among HIV-infected populations. This longitudinal cohort study aimed to investigate the incidence and persistence of Leishmania infection among HIV-infected individuals in an affected area, Trang Province, Southern Thailand. The study also identified risk factors associated with the incidence of Leishmania infection. The study enrolled 373 participants in the HIV clinic, Trang Hospital, who initially tested negative for Leishmania infection during 2015-2016, and 133 individuals initially tested positive for Leishmania infection. Thus, follow-up visits of 506 participants occurred during 2018-2019. Direct Agglutination Test (DAT) and nested PCR (nPCR) identified incidents and persistent cases of Leishmania infection. Cox proportional-hazards regression analyses were performed to assess risk factors for the incidence of Leishmania infection. Among the initially negative group, 12 incident cases comprised one L. orientalis infection and 11 seropositive cases using DAT, resulting in a cumulative incidence of 3.2% and an incidence density of 10.38 per 1000 person-years. Increasing age was a significant predictor of the incidence of Leishmania infection. Five persistent cases comprised one Leishmania donovani complex and four seropositive cases using DAT in the initially positive group, with a cumulative persistence rate of 3.7% and a persistence density of 12.85 per 1000 person-years. All patients were asymptomatic. This study sheds light on the incidence and persistence of Leishmania infection among HIV-infected individuals in Trang Province, Southern Thailand, underscoring the importance of continued monitoring and tailored interventions to mitigate the impact of this co-infection.

Seasonal dynamics, Leishmania diversity, and nanopore-based metabarcoding of blood meal origins in Culicoides spp. in the newly emerging focus of leishmaniasis in Northern Thailand

BACKGROUND

Clinical cases of leishmaniasis caused by Leishmania (Mundinia) parasites have been increasingly reported in Southeast Asia, particularly Thailand. Recent evidence has shown that Leishmania (Mundinia) parasites successfully developed into infective metacyclic promastigotes in Culicoides biting midges, strongly supporting their putative role in disease transmission. However, Culicoides diversity, host preference, and Leishmania prevalence in endemic areas remain largely unknown.

METHODS

We investigated the seasonal dynamics, infection prevalence, and blood meal identification of Culicoides collected from the emerging focus of visceral leishmaniasis in Lampang Province, Northern Thailand, during 2021-2023. Midge samples were molecularly screened for Leishmania using SSU rRNA-qPCR and ITS1-PCR, followed by Sanger plasmid sequencing, and parasite haplotype diversity was analyzed. Host blood meal origins were comparatively identified using host-specific Cytb-PCRs and a nanopore-based metabarcoding approach.

RESULTS

A total of 501 parous and gravid females and 46 blood-engorged ones belonging to at least 17 species of five subgenera (Remmia, Trithecoides, Avaritia, Hoffmania, and Meijerehelea) and two species groups (Shortti and Calvipalpis) were collected with temporal differences in abundance. Leishmania was detected by SSU rRNA-qPCR in 31 samples of at least 11 midge species, consisting of Culicoides oxystoma, C. guttifer, C. orientalis, C. mahasarakhamense, C (Trithecoides) spp., C. innoxius, C. shortti, C. arakawae, C. sumatrae, C. actoni, and C. fulvus, with the overall infection prevalence of 5.7%. The latter six species represent the new records as putative leishmaniasis vectors in Northern Thailand. The ITS1-PCR and plasmid sequencing revealed that Leishmania martiniquensis was predominantly identified in all qPCR-positive species, whereas L. orientalis was identified only in three C. oxystoma samples. The most dominant haplotype of L. martiniquensis in Thailand was genetically intermixed with those from other geographical regions, confirming its globalization. Neutrality test statistics were also significantly negative on regional and country-wide scales, suggesting rapid population expansion or selective sweeps. Nanopore-based blood meal analysis revealed that most Culicoides species are mammalophilic, with peridomestic and wild mammals (cow, pig, deer, and goat-like species) and humans as hosts, while C. guttifer and C. mahasarakhamense fed preferentially on chickens.

CONCLUSIONS

This study revealed seasonal dynamics and sympatric circulation of L. martiniquensis and L. orientalis in different species of Culicoides. Evidence of human blood feeding was also demonstrated, implicating Culicoides as putative vectors of human leishmaniasis in endemic areas. Further research is therefore urgently needed to develop vector control strategies and assess the infection status of their reservoir hosts to effectively minimize disease transmission.

Leishmania Infection among HIV-Infected Patients in a Southern Province of Thailand: A Cross-Sectional Study

Leishmaniasis, a neglected tropical disease, imposes a notable health burden, especially on immunocompromised individuals such as HIV patients. Recognizing its prevalence and risk factors in specific populations is vital for effective prevention. This study in Satun Province, southern Thailand, aimed to ascertain leishmaniasis prevalence and identify associated risks among HIV-infected patients. A cross-sectional study was conducted among 650 HIV-infected individuals at a tertiary care hospital. Data on demographic characteristics, clinical parameters, and potential risk factors were collected. Individual plasma, buffy coat, and saliva samples were collected. Leishmania infection was determined using the direct agglutination test and nested polymerase chain reaction (nPCR) of nPCR-buffy coat and nPCR-saliva. The association between risk factors and Leishmania infection was assessed with logistic regression analysis. The prevalence of Leishmania infection was 8.61% (56/650). Species was identified among 20 HIV-infected patients as follows: Leishmania orientalis (n = 14), Leishmania martiniquensis (n = 4), and Leishmania donovani complex (n = 2). The factors associated with Leishmania infection included age (adjusted odds ratio [OR] = 1.03), intravenous drug use (adjusted OR = 2.39), CD4 cell count <500 cells/mm3 (adjusted OR = 2.40), and a viral load ≥50 copies/mL (adjusted OR = 5.16). The prevalence of Leishmania infection among HIV-infected patients in Satun Province was considerable. These findings underscore the need for integrated care and targeted interventions to address this infection and improve public health outcomes. Further research and collaborative efforts are warranted to develop effective prevention and control strategies for Leishmania infection in the HIV-infected Thai population.

Development of nucleic acid lateral flow immunoassay for duplex detection of Leishmania martiniquensis and Leishmania orientalis in asymptomatic patients with HIV

Leishmaniasis, a neglected tropical disease caused by parasitic protozoa of the Leishmania genus, remains a global health concern with significant morbidity and mortality. In Thailand, the rising incidence of autochthonous leishmaniasis cases involving Leishmania (Mundinia) martiniquensis and novel Leishmania (Mundinia) orientalis underscores the critical need for accurate diagnosis and effective control strategies. This study presents a sensitive and specific nucleic acid lateral flow immunoassay (NALFIA) that integrates a duplex PCR assay with a lateral flow device (LFD) strip format. Targeting the internal transcribed spacer 1 (ITS1) region, known for its unique combination of conserved and variable sequences, this assay employs primers labeled with biotin, digoxigenin, and fluorescein isothiocyanate (FITC) markers, enabling precise species identification and differentiation of these two Leishmania species. Remarkably, the assay achieves a sensitivity that surpasses agarose gel electrophoresis, detecting as few as 10-2 parasite/μL for L. martiniquensis and 10-4 parasite/μL for L. orientalis. Notably, the assay exhibited reliable specificity, revealing no cross-amplification with other major viscerotropic Leishmania species or reference organisms. Evaluation using 62 clinical samples further confirms the effectiveness of the PCR-LFD assay, with a sensitivity of 100% for L. martiniquensis and 83.3% for L. orientalis, and an excellent agreement (κ value = 0.948) with nested PCR. This integrated assay represents a promising advancement in diagnostic tools, offering rapid and accurate results that can significantly contribute to effective disease management and control. Given the increasing relevance of these Leishmania species in current public health scenarios, this assay serves as a valuable tool for both diagnostic and research applications.

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.

Steppe lemmings and Chinese hamsters as new potential animal models for the study of the Leishmania subgenus Mundinia (Kinetoplastida: Trypanosomatidae)

Leishmania, the dixenous trypanosomatid parasites, are the causative agents of leishmaniasis currently divided into four subgenera: Leishmania, Viannia, Sauroleishmania, and the recently described Mundinia, consisting of six species distributed sporadically all over the world infecting humans and/or animals. These parasites infect various mammalian species and also cause serious human diseases, but their reservoirs are unknown. Thus, adequate laboratory models are needed to enable proper research of Mundinia parasites. In this complex study, we compared experimental infections of five Mundinia species (L. enriettii, L. macropodum, L. chancei, L. orientalis, and four strains of L. martiniquensis) in three rodent species: BALB/c mouse, Chinese hamster (Cricetulus griseus) and steppe lemming (Lagurus lagurus). Culture-derived parasites were inoculated intradermally into the ear pinnae and progress of infection was monitored for 20 weeks, when the tissues and organs of animals were screened for the presence and quantity of Leishmania. Xenodiagnoses with Phlebotomus duboscqi were performed at weeks 5, 10, 15 and 20 post-infection to test the infectiousness of the animals throughout the experiment. BALB/c mice showed no signs of infection and were not infectious to sand flies, while Chinese hamsters and steppe lemmings proved susceptible to all five species of Mundinia tested, showing a wide spectrum of disease signs ranging from asymptomatic to visceral. Mundinia induced significantly higher infection rates in steppe lemmings compared to Chinese hamsters, and consequently steppe lemmings were more infectious to sand flies: In all groups tested, they were infectious from the 5th to the 20th week post infection. In conclusion, we identified two rodent species, Chinese hamster (Cricetulus griseus) and steppe lemming (Lagurus lagurus), as candidates for laboratory models for Mundinia allowing detailed studies of these enigmatic parasites. Furthermore, the long-term survival of all Mundinia species in steppe lemmings and their infectiousness to vectors support the hypothesis that some rodents have the potential to serve as reservoir hosts for Mundinia.

Genetic variation and geographic distribution of Leishmania orientalis and Leishmania martiniquensis among Leishmania/HIV co-infection in Thailand

Since 1999, the number of asymptomatic leishmaniasis cases has increased continuously in Thailand, particularly among patients with HIV who are prone to develop symptoms of cutaneous and visceral leishmaniasis further. The asymptomatic infection could play a key role in Leishmania transmission and distribution. Understanding population structure and phylogeographic patterns could be crucially needed to develop effective diagnoses and appropriate guidelines for therapy. In this study, genetic variation and geographic distribution of the Leishmania/HIV co-infected population were investigated in endemic northern and southern Thailand. Interestingly, Leishmania orientalis was common and predominant in these two regions with common regional haplotype distribution but not for the others. Recent population expansion was estimated, probably due to the movement and migration of asymptomatic individuals; therefore, the transmission and prevalence of Leishmania infection could be underestimated. These findings of imbalanced population structure and phylogeographic distribution patterns provide valuable, insightful population structure and geographic distribution of Leishmania/HIV co-infection to empower prevention and control of transmission and expansion of asymptomatic leishmaniasis.

Species diversity of phlebotomine sand flies and sympatric occurrence of Leishmania (Mundinia) martiniquensis, Leishmania (Leishmania) donovani complex, and Trypanosoma spp. in the visceral leishmaniasis focus of southern Thailand

Autochthonous leishmaniasis in Thailand has recently been a public health concern due to an increasing number of new clinical cases. Most indigenous cases were diagnosed with Leishmania (Mundinia) martiniquensis, and Leishmania (Mundinia) orientalis. However, some doubts regarding vector misidentification have arisen and need to be elucidated. Accordingly, we aimed to assess the species composition of sand flies and determine the molecular prevalence of trypanosomatids in the transmission area of leishmaniasis in southern Thailand. In the present study, a total of 569 sand flies were caught from the vicinity of a visceral leishmaniasis patient's house in Na Thawi District, Songkhla Province. Of these, 229 parous and gravid females consisted of Sergentomyia khawi, Se. barraudi, Phlebotomus stantoni, Grassomyia indica, and Se. hivernus, accounting for 31.4%, 30.6%, 29.7%, 7.9%, and 0.4%, respectively. However, Se. gemmea, which has previously been proposed as the most abundant species and putative vector of visceral leishmaniasis, was not found in the present study. Based on ITS1-PCR and sequence analysis, two specimens of Gr. indica and Ph. stantoni showed positive amplification of L. martiniquensis and L. donovani complex, respectively, the first one being presumed indigenous and the second one being not. Anuran Trypanosoma was also molecularly detected using SSU rRNA-PCR and ubiquitously found in sixteen specimens of four dominant sand fly species except for Se. hivernus. The obtained sequences could be phylogenetically categorized into the two major amphibian clades (An04/Frog1 and An01+An02/Frog2). The existence of the monophyletic subgroup and distinct lineage suggests them as novel Trypanosoma species. The TCS network analysis of these anuran Trypanosoma sequences also revealed high haplotype diversity (Hd = 0.925 ± 0.050), but low nucleotide diversity (π = 0.019 ± 0.009). Furthermore, the living anuran trypanosomes were microscopically demonstrated in a single specimen of Gr. indica, supporting the vectorial capacity. Importantly, our data confirmed the scarcity of Se. gemmea and also uncovered, for the first time, the co-circulation of L. martiniquensis, L. donovani complex, and suspected novel anuran Trypanosoma spp. in phlebotomine sand files, implicating their potential role as vectors of trypanosomatid parasites. Therefore, the novel data from this study would greatly facilitate the comprehension of the complexity of trypanosomatid transmission and the establishment of prevention and control measures for this neglected disease more effectively.

Asymptomatic Leishmania infection in humans: A systematic review

BACKGROUND

Leishmaniasis is a highly prevalent neglected tropical disease. It mainly presents as two forms: cutaneous and visceral leishmaniasis, the latter being the most severe form. However, asymptomatic cases of Leishmania infection result in an increase in the underreporting and transmission of the protozoan OBJECTIVES: In this study, articles on the incidence of asymptomatic Leishmania infection were systematically reviewed.

METHODS

The publications identified in the Medline/PubMed and Science Direct databases included 4568 articles. Inclusion, exclusion, and eligibility criterion analysis resulted in 83 articles being retained. These studies were mostly performed in Brazil (n = 26) and India (n = 15).

RESULTS

Several detection techniques have been used for diagnosis. Among the species found were L. infantum and L. donovani, which result in visceral leishmaniasis, and L. amazonensis, L. braziliensis, and L. panamensis. The incidence rates varied between the analyzed locations, largely due to sampling and the presence or absence of endemism in the regions. The largest populations analyzed were in two studies performed in India and Nepal. One of these studies evaluated 32,529 people and the incidence rate was 8.3% (n = 2702), while the other study evaluated 21,267 people and the incidence rate was 1.76% (n = 375). Only 14.28% of the studies investigated leishmaniasis in blood donors. Preexisting diseases have also been reported.

CONCLUSION

The findings of this systematic review present the incidence of cases of asymptomatic Leishmania infection worldwide, in addition to detailing the studies and offering information for researchers and health authorities to seek alternatives to reduce the number of leishmaniasis cases.

Prevalence of visceral leishmaniasis among people with HIV: a systematic review and meta-analysis

Leishmaniasis is a parasitic infection expressing different clinical phenotypes. Visceral leishmaniasis (VL) is considered an opportunistic infection among people with human immunodeficiency virus (HIV). The objective of this review was to identify published data on the prevalence of Leishmania spp. infection among PWH and to define particular determinants that affect critically the epidemiological characteristics of VL-HIV coinfection and, potentially, its burden on public health. Two independent reviewers conducted a systematic literature search until June 30, 2022. Meta-analyses were conducted using random-effects models to calculate the summary prevalence and respective 95% confidence intervals (CI) of leishmaniasis among PWH. Meta-regression analysis was performed to investigate the impact of putative effect modifiers, such as the mean CD4 cell count, on the major findings. Thirty-four studies were eligible, yielding a summary prevalence of 6% (95%CI, 4-11%) for leishmaniasis (n = 1583) among PWH (n = 85,076). Higher prevalence rates were noted in Asia (17%, 95%CI, 9-30%) and America (9%, 95%CI, 5-17%) than in Europe (4%, 95%CI, 2-8%). Prevalence rates were significantly mediated by the age, sex, and CD4 cell count of participants. Heterogeneity remained significant in all meta-analyses (p < 0.0001). In the majority of included studies, people were coinfected with HIV and Leishmania species associated with VL, as opposed to those associated with cutaneous leishmaniasis. No sign of publication bias was shown (p = 0.06). Our summary of published studies on leishmaniasis among PWH is important to provide prevalence estimates and define potential underlying factors that could guide researchers to generate and further explore specific etiologic hypotheses.

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.

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.

Distance-based paper device using combined SYBR safe and gold nanoparticle probe LAMP assay to detect Leishmania among patients with HIV

Asymptomatic visceral leishmaniasis cases increase continuously, particularly among patients with HIV who are at risk to develop further symptoms of leishmaniasis. A simple, sensitive and reliable diagnosis is crucially needed due to risk populations mostly residing in rural communities with limited resources of laboratory equipment. In this study, a highly sensitive and selective determination of Leishmania among asymptomatic patients with Leishmania/HIV co-infection was achieved to simultaneously interpret and semi-quantify using colorimetric precipitates (gold-nanoparticle probe; AuNP-probe) and fluorescence (SYBR safe dye and distance-based paper device; dPAD) in one-step loop-mediated isothermal amplification (LAMP) assay. The sensitivities and specificities of 3 detection methods were equivalent and had reliable performances achieving as high as 95.5%. Detection limits were 10² parasites/mL (0.0147 ng/µL) which were 10 times more sensitive than other related studies. To empower leishmaniasis surveillance as well as prevention and control, this dPAD combined with SYBR safe and gold nanoparticle probe LAMP assay is reliably fast, simple, inexpensive and practical for field diagnostics to point-of-care settings in resource-limited areas which can be set up in all levels of healthcare facilities, especially in low to middle income countries.

Making the Most of Its Short Reads: A Bioinformatics Workflow for Analysing the Short-Read-Only Data of Leishmania orientalis (Formerly Named Leishmania siamensis) Isolate PCM2 in Thailand

Simple Summary

Leishmaniasis is a parasitic disease caused by flagellated protozoa of the genus Leishmania. Multiple genome sequencing platforms have been employed to complete Leishmania genomes at the expense of high cost. This study proposes an integrative bioinformatic workflow for assembling only the short-read data of Leishmania orientalis isolate PCM2 from Thailand and produce an acceptable-quality genome for further genomic analysis. This workflow gives extensive information required for identifying strain-specific markers and virulence-associated genes useful for drug and vaccine development before a more exhaustive and expensive investigation.

Abstract

Background: Leishmania orientalis (formerly named Leishmania siamensis) has been neglected for years in Thailand. The genomic study of L. orientalis has gained much attention recently after the release of the first high-quality reference genome of the isolate LSCM4. The integrative approach of multiple sequencing platforms for whole-genome sequencing has proven effective at the expense of considerably expensive costs. This study presents a preliminary bioinformatic workflow including the use of multi-step de novo assembly coupled with the reference-based assembly method to produce high-quality genomic drafts from the short-read Illumina sequence data of L. orientalis isolate PCM2. Results: The integrating multi-step de novo assembly by MEGAHIT and SPAdes with the reference-based method using the L. enriettii genome and salvaging the unmapped reads resulted in the 30.27 Mb genomic draft of L. orientalis isolate PCM2 with 3367 contigs and 8887 predicted genes. The results from the integrated approach showed the best integrity, coverage, and contig alignment when compared to the genome of L. orientalis isolate LSCM4 collected from the northern province of Thailand. Similar patterns of gene ratios and frequency were observed from the GO biological process annotation. Fifty GO terms were assigned to the assembled genomes, and 23 of these (accounting for 61.6% of the annotated genes) showed higher gene counts and ratios when results from our workflow were compared to those of the LSCM4 isolate. Conclusions: These results indicated that our proposed bioinformatic workflow produced an acceptable-quality genome of L. orientalis strain PCM2 for functional genomic analysis, maximising the usage of the short-read data. This workflow would give extensive information required for identifying strain-specific markers and virulence-associated genes useful for drug and vaccine development before a more exhaustive and expensive investigation.

Non-Endemic Leishmaniases Reported Globally in Humans between 2000 and 2021—A Comprehensive Review

Leishmaniases are human and animal parasitic diseases transmitted by phlebotomine sand flies. Globalization is an important driver of the burden and in the current dynamics of these diseases. A systematic review of articles published between 2000 and 2021 was conducted using the PubMed search engine to identify the epidemiology and clinical management of imported human leishmaniases as a fundamental step to better manage individual cases and traveler and migrant health from a global perspective. A total of 275 articles were selected, representing 10,341 human imported cases. Identified drivers of changing patterns in epidemiology include conflict and war, as well as host factors, such as immunosuppression, natural and iatrogenic. Leishmania species diversity associated with different clinical presentations implies diagnostic and treatment strategies often complex to select and apply, especially in non-endemic settings. Thus, diagnostic and management algorithms for medical clinical decision support are proposed. Increased surveillance of non-endemic cases, whether in vulnerable populations such as refugees/migrants and immunocompromised individuals or travelers, could improve individual health and mitigate the public health risk of introducing Leishmania species into new areas.

Genotypic and phylogenic analyses of cutaneous leishmaniasis in Al Ahsa, Eastern Saudi Arabia during the coronavirus disease 2019 pandemic: First cases of Leishmania tropica with the predominance of Leishmania major

During the coronavirus disease 2019 lockdown period, a surge in sandflies and cutaneous leishmaniasis (CL) cases was observed in Al-Ahsa, Saudi Arabia. Skin punch biopsies were obtained from 100 patients clinically diagnosed with CL in Al-Ahsa who had no travel history in the last 6 months. Impression smears were used following a three-step polymerase chain reaction (PCR) protocol using genus-specific primers targeting kDNA and ITS1. Leishmania speciation was determined by ITS1 PCR/nested PCR-restriction fragment length polymorphism and sequencing. A phylogenetic tree was constructed. The associated patient characteristics were analyzed. Using internal transcribed spacer one (ITS1)-PCR/nested PCR, 98 cases were considered true-positive CL. Leishmania major was the predominant species, and Leishmania tropica was identified in three cases. Microscopy had poor sensitivity and perfect specificity. Direct ITS1-PCR missed nine cases. Sex, residence, and treatment outcome were significantly associated with the occurrence of Leishmania; distribution of skin lesion(s) and treatment outcome were significantly associated with Leishmania genotype. This is the first time that L. tropica was identified as a cause of CL in human in Al-Ahsa, in addition to the predominant zoonotic species, L. major. We recommend using ITS1-nested PCR for negative cases by ITS1-PCR. Further exploration of Leishmania transmission dynamics in vectors and reservoir animals is essential for designing effective preventive measures.

Comparative Draft Genomes of Leishmania orientalis Isolate PCM2 (Formerly Named Leishmania siamensis) and Leishmania martiniquensis Isolate PCM3 from the Southern Province of Thailand

Simple Summary

This study successfully sequenced the draft genomes of the southern isolates of Leishmania orientalis and Leishmania martiniquensis in Thailand. The comparison with the genomes of the northern isolates revealed species-level similarity with a level of genome and proteome variation, suggesting the different emerging strains. Comparing the proteins of these southern strains to those of the northern ones and 14 other Leishmania species showed six protein groups with numerous unique proteins: 53 for the southern strain PCM2 of L. orientalis and 97 for the strain PCM3 of L. martiniquensis. Some of these proteins were related to virulence, drug resistance, drug target, and stress response, which could be targeted for further experimental characterization. Therefore, the findings could initiate further genetic and population genomic investigation, and the close monitoring of L. orientalis and L. martiniquensis in Thailand and neighboring regions.

Abstract

(1) Background: Autochthonous leishmaniasis, a sandfly-borne disease caused by the protozoan parasites Leishmania orientalis (formerly named Leishmania siamensis) and Leishmania martiniquensis, has been reported for immunocompromised and immunocompetent patients in the southern province of Thailand. Apart from the recent genomes of the northern isolates, limited information is known on the emergence and genetics of these parasites. (2) Methods: This study sequenced and compared the genomes of L. orientalis isolate PCM2 and L. martiniquensis isolate PCM3 with those of the northern isolates and other 14 Leishmania species using short-read whole-genome sequencing methods and comparative bioinformatic analyses. (3) Results: The genomes of the southern isolates of L. orientalis and L. martiniquensis were 30.01 Mbp and 32.39 Mbp, and the comparison with the genomes of the northern isolates revealed species-level similarity with a level of genome and proteome variation, suggesting the different strains. Comparative proteome analysis showed six protein groups with 53 unique proteins for the strain PCM2 and 97 for the strain PCM3. Certain proteins were related to virulence, drug resistance, and stress response. (4) Conclusion: Therefore, the findings could indicate the need for more genetic and population genomic investigation, and the close monitoring of L. orientalis and L. martiniquensis in Thailand and neighboring regions.

Prevalence and associated risk factors of Leishmania infection among immunocompetent hosts, a community-based study in Chiang Rai, Thailand

Background

Leishmaniasis is an emerging infectious disease reported in the north and south of Thailand of which patients with HIV/AIDS are a high risk group for acquiring the infection. A lack of information regarding prevalence, and the risk association of Leishmania infection among asymptomatic immunocompetent hosts needs further investigation. Information on potential vectors and animal reservoirs in the affected areas is also important to control disease transmission.

Methods

An outbreak investigation and a cross-sectional study were conducted following one index case of cutaneous leishmaniasis (CL) caused by L. martiniquensis in an immunocompetent male patient reported in August 2015, Chiang Rai Province, Thailand. From September to November 2015, a total of 392 participants at two study areas who were related to the index case, 130 students at a semi-boarding vocational school and 262 hill tribe villagers in the patient’s hometown, were recruited in this study. The nested internal transcribed spacer 1-PCR (ITS1-PCR) was performed to detect Leishmania DNA in buffy coat, and nucleotide sequencing was used to identify species. Antibody screening in plasma was performed using the Direct Agglutination Test (DAT), and associated risk factors were analyzed using a standardized questionnaire. Captured sandflies within the study areas were identified and detected for Leishmania DNA using nested ITS1-PCR. Moreover, the animal reservoirs in the study areas were also explored for Leishmania infection.

Results

Of 392 participants, 28 (7.1%) were positive for Leishmania infection of which 1 (4.8%) was L. martiniquensis, 12 (57.1%) were L. orientalis and 8 (38.1%) were Leishmania spp. Of 28, 15 (53.6%) were DAT positive. None showed any symptoms of CL or visceral leishmaniasis. Risk factors were associated with being female (adjusted odds ratio, AOR 2.52, 95%CI 1.01–6.26), increasing age (AOR 1.05, 95%CI 1.02–1.08), having an animal enclosure in a housing area (AOR 3.04, 95%CI 1.13–8.22), being exposed to termite mounds (AOR 3.74, 95%CI 1.11–12.58) and having domestic animals in a housing area (AOR 7.11, 95%CI 2.08–24.37). At the semi-boarding vocational school, six Sergentomyia gemmea samples were PCR positive for DNA of L. orientalis and one S. gemmea was PCR positive for DNA of L. donovani/L. infantum. Additionally, one Phlebotomus stantoni was PCR positive for DNA of L. martiniquensis, and one black rat (Rattus rattus) was PCR positive for DNA of L. martiniquensis.

Conclusion

This information could be useful for monitoring Leishmania infection among immunocompetent hosts in affected areas and also setting up strategies for prevention and control. A follow-up study of asymptomatic individuals with seropositive results as well as those with positive PCR results is recommended.

This is the first community-based study investigating the prevalence and associated risk factors of Leishmania infection among immunocompetent individuals, demonstrating the situation of Leishmania infection in endemic areas of Thailand. An outbreak investigation and a cross-sectional study were conducted following one index case of cutaneous leishmaniasis (CL) caused by L. martiniquensis in an immunocompetent male patient reported in August 2015, Chiang Rai Province, Thailand. Of 392 participants, 28 (7.1%) were positive for Leishmania infection of which 1 (4.8%) was L. martiniquensis, 12 (57.1%) were L. orientalis and 8 (38.1%) were Leishmania spp. The factors associated with Leishmania infection included being female, increasing age, having an animal enclosure in a housing area, being exposed to termite mounds and having domestic animals in a housing area. This information revealed the first burden and risk factors of Leishmania infection among immunocompetent individuals in Thailand and highlighted the urgent need for effective interventions to prevent and control the disease in high risk populations in endemic areas.

Development of loop-mediated isothermal amplification (LAMP) assay using SYBR safe and gold-nanoparticle probe for detection of Leishmania in HIV patients

Asymptomatic leishmaniasis cases have continuously increased, especially among patients with HIV who are at risk to develop further symptoms of cutaneous and visceral leishmaniasis. Thus, early diagnosis using a simple, sensitive and reliable diagnostic assay is important because populations at risk mostly reside in rural communities where laboratory equipment is limited. In this study, the highly sensitive and selective determination of Leishmania infection in asymptomatic HIV patients was achieved using dual indicators (SYBR safe and gold-nanoparticle probe; AuNP-probe) in one-step LAMP method based on basic instruments. The assay can be simply evaluated under the naked eye due to clear interpretation of fluorescent emission of LAMP-SYBR safe dye-complex and colorimetric precipitate of specific AuNP-probes. The sensitivities and specificities of fluorescent SYBR safe dye and AuNP-probe indicators were equal, which were as high as 94.1 and 97.1%, respectively. Additionally, detection limits were 10² parasites/mL (0.0147 ng/µL), ten times more sensitivity than other related studies. To empower leishmaniasis surveillance, this inexpensive one-step SYBR safe and AuNP-LAMP assay is reliably fast and simple for field diagnostics to point-of-care settings, which can be set up in all levels of health care facilities including resource limited areas, especially in low to middle income countries.

Cutaneous Leishmaniasis Outbreak Investigation in Hajjah Governorate, Yemen, in 2018: Case-Control Study

Background

Cutaneous leishmaniasis (CL) is endemic in Yemen. About 4440 cases were reported in 2019. On July 23, 2018, a Hajjah governorate surveillance officer notified the Ministry of Public Health and Population about an increase in the number of CL cases in Bani-Oshb, Kuhlan district, Hajjah governorate. On July 24, 2018, Yemen Field Epidemiology Training Program sent a team to perform an investigation.

Objective

We aimed to describe a CL outbreak in Hajjah governorate and determine its risk factors.

Methods

A descriptive study and case-control study (1:1 ratio) were conducted. Cases included people who met the suspected or confirmed case definition of the World Health Organization and lived in Bani-Oshb subdistrict during the period from August 2017 to July 2018. Controls included people living for at least 1 year in Bani-Oshb without new or old skin lesions. Crude odds ratios (cORs) and adjusted odds ratios (aORs) with 95% CI were used to test the significance of associations.

Results

We identified 30 CL cases. Among the 30 patients, 7 (23%) were younger than 5 years, 17 (57%) were 5 to 14 years, 17 (57%) were females, and 23 (77%) had one lesion. The attack rate was 7 per 1000 population in the age group <15 years and 1 per 1000 population in the age group ≥15 years. On bivariate analysis, the following factors were significantly associated with CL: female gender (cOR 5.2, 95% CI 1.7-16.5), malnutrition (cOR 5.2, 95% CI 1.7-16.5), not using a bed net (cOR 14.5, 95% CI 1.7-122.4), poor house lighting (cOR 6.4, 95% CI 2.1-19.7), poor house hygiene (cOR 11.2, 95% CI 3.1-40.7), poor sanitation (cOR 14.5, 95% CI 1.7-122.4), living in houses without window nets (cOR 5.2, 95% CI 1.3-21.2), plantation around the house (cOR 6.5, 95% CI 2.1-20.5), animal barn inside or close to the house (cOR 9.3, 95% CI 1.9-46.7), raising animals (cOR 8.1, 95% CI 1.6-40.7), and having animal dung in or near the house (cOR 6.8, 95% CI 1.7-27.7). The following risk factors remained significant on multivariate stepwise analysis: female gender (aOR 22.7, 95% CI 1.6-320.5), malnutrition (aOR 17.2, 95% CI 1.3-225.8), poor house hygiene (aOR 45.6, 95% CI 2.5-846.4), plantation around the house (aOR 43.8, 95% CI 1.9-1009.9), and raising animals (aOR 287.1, 95% CI 5.4-15205.6).

Conclusions

CL was endemic in Hajjah governorate, and an increase in cases was confirmed. Many individual, housing, and animal related factors were shown to contribute to CL endemicity. Implementation of control measures directed toward altering the factors favoring contact among vectors, reservoirs, and susceptible humans is strongly recommended to control future outbreaks.

A Molecular Modeling Approach to Identify Potential Antileishmanial Compounds Against the Cell Division Cycle (cdc)-2-Related Kinase 12 (CRK12) Receptor of Leishmania donovani

The huge burden of leishmaniasis caused by the trypanosomatid protozoan parasite Leishmania is well known. This illness was included in the list of neglected tropical diseases targeted for elimination by the World Health Organization. However, the increasing evidence of resistance to existing antimonial drugs has made the eradication of the disease difficult to achieve, thus warranting the search for new drug targets. We report here studies that used computational methods to identify inhibitors of receptors from natural products. The cell division cycle-2-related kinase 12 (CRK12) receptor is a plausible drug target against Leishmania donovani. This study modelled the 3D molecular structure of the L. donovani CRK12 (LdCRK12) and screened for small molecules with potential inhibitory activity from African flora. An integrated library of 7722 African natural product-derived compounds and known inhibitors were screened against the LdCRK12 using AutoDock Vina after performing energy minimization with GROMACS 2018. Four natural products, namely sesamin (NANPDB1649), methyl ellagic acid (NANPDB1406), stylopine (NANPDB2581), and sennecicannabine (NANPDB6446) were found to be potential LdCRK12 inhibitory molecules. The molecular docking studies revealed two compounds NANPDB1406 and NANPDB2581 with binding affinities of -9.5 and -9.2 kcal/mol, respectively, against LdCRK12 which were higher than those of the known inhibitors and drugs, including GSK3186899, amphotericin B, miltefosine, and paromomycin. All the four compounds were predicted to have inhibitory constant (Ki) values ranging from 0.108 to 0.587 μM. NANPDB2581, NANPDB1649 and NANPDB1406 were also predicted as antileishmanial with Pa and Pi values of 0.415 and 0.043, 0.391 and 0.052, and 0.351 and 0.071, respectively. Molecular dynamics simulations coupled with molecular mechanics Poisson-Boltzmann surface area (MM/PBSA) computations reinforced their good binding mechanisms. Most compounds were observed to bind in the ATP binding pocket of the kinase domain. Lys488 was predicted as a key residue critical for ligand binding in the ATP binding pocket of the LdCRK12. The molecules were pharmacologically profiled as druglike with inconsequential toxicity. The identified molecules have scaffolds that could form the backbone for fragment-based drug design of novel leishmanicides but warrant further studies to evaluate their therapeutic potential.

Simplified closed tube loop mediated isothermal amplification (LAMP) assay for visual diagnosis of Leishmania infection

In Thailand, asymptomatic leishmaniasis cases have continuously increased, especially among patients with HIV at risk to develop further symptoms of cutaneous and visceral leishmaniasis. Thus, earlier diagnosis using a simple, sensitive and reliable diagnostic tool is needed because populations at risk mostly reside in rural communities where only basic laboratory equipment is available for health care services. In this present study, a closed tube loop mediated isothermal amplification (LAMP) was developed using a piece of parafilm placed between the dye and LAMP reaction mixture to form semi-layer that partially secured SYBR green I from spilling during amplification. No post-amplification preparation was required and accidental spill of the dye during LAMP amplification was prevented. The result could be visually interpreted under visible and UV lights after dye spinning down. The semi-layer modification of a closed tube LAMP showed successful amplification of Leishmania DNA with clear interpretation using both color and fluorescence dyes when observing by the naked eye. The sensitivity and specificity were as high as 94.4 and 96.9%, respectively whereas detection limits were 10² parasites/mL being ten fold more sensitive than other related studies. This user-friendly inexpensive approach is affordable and suitable for empowering leishmaniasis surveillance without the need of expensive devices in all levels of hospitals, including health services, as well as fieldwork, especially in low income countries.

Risk Factors of Leishmania Infection among HIV-Infected Patients in Trang Province, Southern Thailand: A Study on Three Prevalent Species

There are two main species of Leishmania reported in Thailand, that is, Leishmania siamensis and Leishmania martiniquensis. Moreover, leishmaniasis cases caused by Leishmania donovani complex were also reported. There is still a lack of information concerning risk factors of Leishmania infection in Thailand. This study aimed to identify the risk factors of Leishmania infection caused by these three species among HIV-infected patients. A cross-sectional study was conducted in HIV clinic at Trang Hospital, Thailand. Nested PCR and sequencing were performed to detect Leishmania DNA in blood and saliva samples and identify Leishmania species. A standardized questionnaire was used to interview individuals. A total of 526 patients were recruited in this study. Sixty-three (12.0%) were positive for L. siamensis, 24 (4.6%) were positive for L. martiniquensis, and 23 (4.4%) were positive for L. donovani complex. Risk factors of L. siamensis infection included using intravenous drug (adjusted odds ratio [AOR] 2.01, 95% CI: 1.01-4.02). Risk factors of L. martiniquensis infection included female gender (AOR 4.23, 95% CI: 1.52-11.75), using recreational drug (AOR 3.43, 95% CI: 1.00-11.74), and having comorbidities (AOR 4.94, 95% CI: 2.00-12.21). Risk factors of L. donovani complex infection included having opportunistic infection (AOR 4.22, 95% CI: 1.00-17.79), CD4 count 200-500 cells/mm³ (AOR 3.64, 95% CI: 1.14-6.86), and not using insect repellent (AOR 3.04, 95% CI: 1.08-8.58). This study identified the risk factors of Leishmania infection caused by three Leishmania species in Thailand. The data could be useful for disease prevention and control. Further studies on trends of Leishmania infection and preventive measures are recommended.

Outwitting an Old Neglected Nemesis: A Review on Leveraging Integrated Data-Driven Approaches to Aid in Unraveling of Leishmanicides of Therapeutic Potential

The global prevalence of leishmaniasis has increased with skyrocketed mortality in the past decade. The causative agent of leishmaniasis is Leishmania species, which infects populations in almost all the continents. Prevailing treatment regimens are consistently inefficient with reported side effects, toxicity and drug resistance. This review complements existing ones by discussing the current state of treatment options, therapeutic bottlenecks including chemoresistance and toxicity, as well as drug targets. It further highlights innovative applications of nanotherapeutics-based formulations, inhibitory potential of leishmanicides, anti-microbial peptides and organometallic compounds on leishmanial species. Moreover, it provides essential insights into recent machine learning-based models that have been used to predict novel leishmanicides and also discusses other new models that could be adopted to develop fast, efficient, robust and novel algorithms to aid in unraveling the next generation of anti-leishmanial drugs. A plethora of enriched functional genomic, proteomic, structural biology, high throughput bioassay and drug-related datasets are currently warehoused in both general and leishmania-specific databases. The warehoused datasets are essential inputs for training and testing algorithms to augment the prediction of biotherapeutic entities. In addition, we demonstrate how pharmacoinformatics techniques including ligand-, structure- and pharmacophore-based virtual screening approaches have been utilized to screen ligand libraries against both modeled and experimentally solved 3D structures of essential drug targets. In the era of data-driven decision-making, we believe that highlighting intricately linked topical issues relevant to leishmanial drug discovery offers a one-stop-shop opportunity to decipher critical literature with the potential to unlock implicit breakthroughs.

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.

In vitro growth characteristics and morphological differentiation of Leishmania martiniquensis promastigotes in different culture media

The protozoan hemoflagellate, Leishmania martiniquensis, is the causative agent of cutaneous and visceral leishmaniasis among humans. This parasite was first isolated from an autochthonous case of cutaneous leishmaniasis in Martinique Island (French West Indies) in 1995 and its taxonomical position was later established in 2002. At present, the emergence of this globally infectious disease caused by L.martiniquensis raises serious concerns and has gained attention from the national public health policy. Epidemiological studies indicated that Thailand is one of the endemic areas of L.martiniquensis with hundreds of cases, both symptomatic and asymptomatic, have been reported among patients positive for HIV/AIDS. Information on its basic biology including suitable conditions for parasite propagation is limited. To assess this, we used four established media, that is, Medium 199 (M199), RPMI 1640 medium (RPMI), Grace's insect medium (GIM), and Schneider's insect medium (SIM) to investigate the promastigote growth by evaluating the growth characteristics, viability, and kinetics of stage differentiation in each medium. The findings from this study showed that parasites growing in different media exhibited different biological characteristics, which would be suitable for very specific research purposes, i.e., RPMI; for long term parasite maintenance, M199; for mass culture of parasites, M199 and GIM; for initial isolation of the parasites in clinical specimens, and SIM; for metacyclogenesis study.

Pre-travel counseling for immunocompromised travelers: A 12-year single-center retrospective review

BACKGROUND

Immunocompromised travelers (ICTs) are medically complex and challenging for travel medicine providers. Our study hypothesizes that ICTs have high-risk travel itineraries and do not have adequate immunity against vaccine-preventable infections.

METHODS

This retrospective review of 321 ICTs from 2004 to 2015 included patients with solid organ transplant (SOT, n = 134), connective tissue disease (CTD, n = 121), inflammatory bowel disease (IBD, n = 46), and human immunodeficiency virus (HIV, n = 20). Variables included immunosuppressive medications, hepatitis A and B vaccination and serology, gamma-globulin use, and antimalarial and antidiarrheal prophylaxis. Chi-square analysis was used for categorical variables and Kruskal-Wallis for continuous variables.

RESULTS

Malaria-endemic regions accounted for 38.9% (125/321) of travel destinations. High-risk activities were planned by 37.4% (120/321) of travelers. A significant proportion of HIV patients [70.0% (14/20)] visited friends and relatives, whereas other ICTs traveled for tourism. Hepatitis A and B vaccination rates were 77.3% (248/321) and 72.3% (232/321). Post-vaccination hepatitis A and B serologic testing were completed by 66.1% (41/62) and 61.1% (11/18) of travelers, respectively.

CONCLUSION

ICTs demonstrate differences in travel patterns and risk. Serologic testing was uncommon, and vaccination rates were low. Providers should screen ICTs early for upcoming travel plans and advise vaccine completion prior to departure.

Detection of Leishmania DNA in saliva among patients with HIV/AIDS in Trang Province, southern Thailand

Leishmaniasis is a neglected tropical disease causing opportunistic infection among patients with HIV/AIDS. The fatal form of this disease is visceral leishmaniasis (VL). DNA of Leishmania can be detected in saliva, for which the collection is noninvasive and requires little expertise. This study aimed to evaluate the sensitivity and specificity of a nested-PCR to amplify the Internal Transcribed Spacer 1 (ITS1) to detect Leishmania DNA in paired saliva and buffy coat samples of 305 Thai patients with HIV/AIDS in Trang Hospital, Trang Province, southern Thailand. For asymptomatic Leishmania infection among Thai patients with HIV/AIDS, the sensitivity and specificity of the nested-PCR-ITS1 in buffy coat were 73.9 and 100%, respectively. However, the sensitivity in saliva was 26.1% and specificity was 100%. Using the nested-PCR-ITS1, saliva and buffy coat samples showed positive agreement in only 52.0% of patients. Saliva tested results with the nested-PCR-ITS1 showed positive agreement with the Direct Agglutination Test (DAT) in 46.5% of patients. Only 12.1% of the samples showed positive agreement for Leishmania infection among all the three tests: saliva, buffy coat and DAT results. Using nucleotide sequencing, at least three species of Leishmania infection were identified in saliva, i.e., L. siamensis (n = 28), L. martiniquensis (n = 9), and L. donovani complex (n = 1). As a result, buffy coat still appears to be a better specimen to diagnose asymptomatic VL infection among individuals with HIV. However, the use of both buffy coat and saliva together as clinical specimens would increase the sensitivity of Leishmania detection.

Detection of DNA of Leishmania siamensis in Sergentomyia (Neophlebotomus) iyengari (Diptera: Psychodidae) and Molecular Identification of Blood Meals of Sand Flies in an Affected Area, Southern Thailand

In Thailand, leishmaniasis is an emerging vector-borne disease that has become a public health concern. In related epidemiological surveys to identify potential Leishmania vectors in the affected areas, DNA of Leishmania martiniquensis (Kinetoplastida: Trypanosomatidae) was detected in Sergentomyia (Neophebotomus) gemmea (Diptera: Psychodidae) and Sergentomyia (Parrotomyia) barraudi (Diptera: Psychodidae). Recently, a more elaborate study was conducted in the same areas that included sand fly species identification, screening sand flies for the presence of Leishmania DNA and blood meal analysis to identify potential reservoir hosts directed toward assessing the risk of human infection. Twenty-nine archived pools of sand flies collected in Hat Samran District, Trang Province were used in this study. Sand fly species were confirmed using PCR encompassing regions within the mitochondrial DNA. Leishmania DNA was detected using PCR of the heat shock protein 70 region (hsp70-PCR) and blood meal identification was performed using PCR of the cyt b gene of vertebrate mitochondrial DNA (cytb-nd1-PCR) and human-specific AluYb8 repeat (AluYb8-PCR). Four sand fly species were confirmed, i.e., Phlebotomus (Anaphlebotomus) stantoni (Diptera: Psychodidae), S. barraudi, Sergentomyia (Neophlebotomus) iyengari (Diptera: Psychodidae), and S. gemmea. Leishmania siamensis was detected in one female S. iyengari. Only human blood was detected in P. stantoni and S. gemmea, while both sun skink (Mabuya multifasciata) and human blood were detected in S. iyengari. In this study, we showed that S. iyengari could be a potential vector of L. siamensis infection among humans.

Leishmaniasis recidivans by Leishmania tropica in Central Rift Valley Region in Kenya

OBJECTIVES

This study sought to determine the endemic Leishmania species, the clinical features of cutaneous leishmaniasis (CL) in the Central Rift Valley in Kenya and to give an account on unresponsiveness to treatment in the region.

METHODS

Participants were clinically identified and grouped into untreated, classical and recidivate based on clinical manifestation and clinical data. Leishmaniasis recidivans lesions were scaly hyperemic papules that appeared before the classic lesion had healed or after healing. The demographics and socio-economic data were recorded and lesion scraping samples screened through microscopy and Internal Transcribed Spacer 1-PCR. Leishmania species were identified using Restriction Fragment Length Polymorphism.

RESULTS

A total of 52 participants were sampled, of which, 44.2% of the cases were recidivate and L. tropica the only species identified. All patients had been treated using sodium stibogluconate (SSG) which is the recommended first-line drug in Kenya. 60% of the patients experienced prolonged exposure to the drug (>30 days).

CONCLUSION

L. tropica is the endemic Leishmania species for CL leading to classical and leishmaniasis recidivans. Treatment of CL in the area is not effective hence, alternative measures/therapy should be considered to cope with the unresponsiveness.

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.