The applicability of real-time PCR in the diagnostic of cutaneous leishmaniasis and parasite quantification for clinical management: Current status and perspectives

High detection rate of parasitic load by qPCR targeting 18S rDNA in blood of patients with active leishmaniasis lesions

This study aimed to standardize qPCR techniques using these molecular markers kDNA and 18S rDNA across three sample types: peripheral blood, guanidine-treated blood, and tissue. The secondary objective is to evaluate the performance of 18S rDNA target in samples from 46 patients with confirmed tegumentary leishmaniasis. After obtaining the standard curve from reference strains with Leishmania, qPCR curves were standardizations and the Cts results of the patient samples were described using abstract measures. Specific specification equations (EEG) with normal distribution and identity link function were constructed to compare each type of clinical sample. To identify the differences among samples and techniques, multiple comparisons with Bonferroni post-test was performed. The kDNA and 18S rDNA demonstrated high sensitivity, detecting as few as 10⁻1 parasites/mL. However, 18S rDNA showed limited species discrimination. qPCR performance was evaluated using blood and tissue samples, showing a sensitivity of 54.2% in blood, 12.5% in guanidine-treated blood, and 86.4% in tissue. qPCR agreement with the 18S rDNA target with the three types of samples, positive and negative, in relation to screening were 56.2% in blood, 31.8% in guanidine- blood and tissue 78.6%. As for true positives (PPV), tissue samples presented a probability percentage of individuals being sick of 86.4%, while in blood it was 81.3%. The results underscore the importance of molecular diagnostics in blood samples, improving the accuracy and monitoring of tegumentary leishmaniasis.

Formulation, in vitro evaluation and therapeutic effect of chitosan coated pluronic F127 micelles containing miltefosine for the treatment of visceral leishmaniasis in domestic dogs naturally infected by Leishmania infantum

There are a limited number of chemotherapeutic agents for the treatment canine visceral leishmaniasis (CVL). This study aimed to formulate and assess micellar formulation of miltefosine (MTF) to increase antileishmanial therapeutic effects in dogs naturally infected by Leishmania (L) infantum for the first time. MTF loaded pluronic F127 (PF/MTF) micelles were formulated and coated with chitosan (Cs/PF/MTF). Toxicity of compounds was evaluated. The in vitro and in vivo antileishmanial effect of Cs/PF/MTF was examined in L. infantum promastigotes and amastigotes as well as naturally infected dogs by L. infantum. In-vitro efficacy studies in promastigotes and amastigotes demonstrated that inhibitory concentration (IC50) of Cs/PF/MTF was significantly lower in comparison to miltefosine. In vivo data showed that Cs/PF/MTF is more effective against CVL compared with miltefosine alone. The result of this study indicated that intravenous injection of new formulation of Cs/PF/MTF was tolerated and treated on L. infantum naturally infected dogs with the dosages of 170 μg/kg daily for 28 days.

Diagnostic techniques for visceral leishmaniasis: An overview of methods used in East Africa

Leishmanias is a parasitic infection caused by a protozoan belonging to the genus Leishmania and transmitted by sand fly, Phlebotomus fly in the old world and Lutzomyia in the New world. The disease is prevalent in the tropics, subtropics, and Southern Europe, where it affects about 1.5 million to 2 million people annually. India, Bangladesh, Sudan, South Sudan, Brazil and Ethiopia account for up to 90% of all the VL cases. While Leishmania cases in Asia are declining, cases in East Africa especially in Somalia, Sudan, South Sudan, Ethiopia and Kenya have been increasing. The rise in East African cases is partially attributed to ongoing armed conflicts especially in Somalia, Sudan and Southern Sudan, which has displaced people and increased their exposure to sand fly bites. Migration from endemic to non-endemic regions, misdiagnosis, famine, malnutrition, climate change and an increase in HIV cases are other contributing factors. The clinical diagnosis of Leishmania in East Africa combines the patient's clinical signs with either serological or parasitological test, with rK39 strip and microscopy being the major methods used. Diagnosis of the condition remains challenging, as current techniques have limitations, including the inability to detect parasites in tissue, the need for specialized expertise, prohibitive costs of testing equipment, low antibody titers, and the risk of misdiagnosis due to co-infections with diseases such as HIV, tuberculosis, malaria and typhoid. Various techniques, including serological and molecular parasitological methods, have been employed in attempts to address these challenges, but with limited success. This article therefore, reviews some of the techniques that have been used in Leishmania diagnosis in East Africa and discusses other available new techniques with aim of overcoming the current challenges.

Evaluation of Loopamp Leishmania detection kit for the diagnosis of cutaneous leishmaniasis in Ethiopia

BACKGROUND

Cutaneous leishmaniasis (CL) in Ethiopia and some parts of Kenya is predominantly caused by Leishmania aethiopica. While skin-slit (SS) microscopy is routinely used for CL diagnosis, more sensitive molecular tests are available. The Loopamp™ Leishmania detection kit (Loopamp) is a robust loop-mediated isothermal amplification (LAMP) assay with the potential for implementation in primary healthcare facilities. In this study, we comparatively assessed the diagnostic accuracy of four methods currently used to diagnose CL: Loopamp, kinetoplast DNA (kDNA) PCR, spliced leader RNA (SL-RNA) PCR and SS microscopy.

METHODS

A study on 122 stored tape disc samples of suspected CL patients was conducted in Gondar, northwestern Ethiopia. Routine SS microscopy results were obtained from all patients. Total nucleic acids were extracted from the tapes and subjected to PCR testing targeting kDNA and SL-RNA, and Loopamp. Diagnostic accuracy was calculated with SS microscopy as a reference test. The limit of detection (LoD) of Loopamp and kDNA PCR were determined for cultured L. aethiopica and Leishmania donovani.

RESULTS

Of the 122 patients, 64 (52.5%) were identified as CL cases based on SS microscopy. Although the PCR tests showed a sensitivity of 95.3% (95% confidence interval [CI] 91.6-99.1), Loopamp only had 48.4% (95% CI 39.6-57.3) sensitivity and 87.9% (95% CI 82.1-93.7) specificity. The LoD of Loopamp for L. donovani was 100-fold lower (20 fg/µl) than that for L. aethiopica (2 pg/µl).

CONCLUSIONS

The Loopamp™ Leishmania detection kit is not suitable for the diagnosis of CL in Ethiopia, presumably due to a primer mismatch with the L. aethiopica 18S rRNA target. Further research is needed to develop a simple and sensitive point-of-care test that allows the decentralization of CL diagnosis in Ethiopia.

Non-invasive urine-based ELISA using a recombinant Leishmania protein to diagnose tegumentary leishmaniasis

The diagnosis of tegumentary leishmaniasis (TL) is hampered by variable sensitivity and/or specificity of the tests. Serological assays are suitable to diagnose visceral leishmaniasis (VL); however, they present low performance for the detection of TL cases. Additionally, blood collection to obtain patient serum represents a challenge, as it is an invasive and uncomfortable procedure, requiring laboratorial infrastructure and trained professionals. In this context, the present study proposed to evaluate patient urine to detect TL, given that this analyte has proven to be effective in ELISA experiments for the detection of VL cases. For this, a Leishmania protein called LiHyV, two specific B-cell epitopes derived from protein amino acid sequence, and a Leishmania antigenic extract (SLA) were used as antigens. A total of 215 paired urine and serum samples were evaluated, and results showed that, when serum was employed as an analyte, rLiHyV, Peptide1, Peptide2, and SLA presented a sensitivity of 85 %, 29 %, 58 %, and 31 %, respectively, and a specificity of 97.5 %, 98 %, 100 %, and 97.5 %, respectively, in the diagnosis of TL. When urine was used, rLiHyV, Peptide1, Peptide2, and SLA presented a sensitivity of 95 %, 74 %, 67 %, and 52 %, respectively, and a specificity of 100 %, 99 %, 98 %, and 86 %, respectively. In conclusion, preliminary data suggest that urine could be considered as an alternative biological sample for the detection of TL cases.

A real-time PCR for quantification of parasite burden and its correlations with clinical characteristics and anti-rKRP42 IgG level in cutaneous leishmaniasis in Sri Lanka

In visceral and mucocutaneous leishmaniasis, humoral immune response can reflect disease severity and parasite burden. Cutaneous leishmaniasis (CL) in Sri Lanka is caused by a usually visceralizing parasite, Leishmania donovani. We assessed the parasite burden (relative quantity-RQ) in 190 CL patients using quantitative real-time PCR (qPCR-with primers designed for this study) and smear microscopy, then correlated it with clinical parameters and IgG response. RQ of parasite DNA was determined with human-specific glyceraldehyde 3-phosphate dehydrogenase (GAPDH) as the internal control. The qPCR sensitivity was tested with serially diluted DNA from cultured L. donovani parasites. Smears were assigned a score based on number of parasites per high power field. Data from previous studies were used for comparison and correlation; nested Internal Transcribed Spacer 1 (ITS1) PCR as reference standard (RS) and IgG antibody titers to the Leishmania rKRp42 antigen as the immune response. The qPCR amplified and quantified 86.8% of the samples while demonstrating a fair and significant agreement with ITS1-PCR and microscopy. Parasite burden by qPCR and microscopy were highly correlated (r = 0.76; p = 0.01) but showed no correlation with the IgG response (r = 0.056; p = 0.48). Corresponding mean RQs of IgG titers grouped by percentiles, showed no significant difference (p = 0.93). Mean RQ was higher in early lesions (p = 0.04), decreased with lesion size (p = 0.12) and slightly higher among papules, nodules and wet ulcers (p = 0.72). Our study established qPCR's efficacy in quantifying parasite burden in Sri Lankan CL lesions but no significant correlation was observed between the parasite burden and host IgG response to the Leishmania rKRP42 antigen.

Neglected tropical disease (NTD) diagnostics: current development and operations to advance control

Neglected tropical diseases (NTDs) have become important public health threats that require multi-faceted control interventions. As late treatment and management of NTDs contribute significantly to the associated burdens, early diagnosis becomes an important component for surveillance and planning effective interventions. This review identifies common NTDs and highlights the progress in the development of diagnostics for these NTDs. Leveraging existing technologies to improve NTD diagnosis and improving current operational approaches for deployment of developed diagnostics are crucial to achieving the 2030 NTD elimination target. Point-of-care NTD (POC-NTD) diagnostic tools are recommended preferred diagnostic options in resource-constrained areas for mapping risk zones and monitoring treatment efficacy. However, few are currently available commercially. Technical training of remote health care workers on the use of POC-NTD diagnostics, and training of health workers on the psychosocial consequences of these diagnostics are critical in harnessing POC-NTD diagnostic potential. While the COVID-19 pandemic has challenged the possibility of achieving NTD elimination in 2030 due to the disruption of healthcare services and dwindling financial support for NTDs, the possible contribution of NTDs in exacerbating COVID-19 pandemic should motivate NTD health system strengthening.

Application of CL Detect™ rapid test for diagnosis and liposomal amphotericin B for treatment of cutaneous leishmaniasis: A retrospective analysis from a tertiary care centre in a non-endemic area in India

Background Increasing urbanisation has led to the occurrence of cutaneous leishmaniasis (CL) in new areas, which was otherwise localised to endemic areas. Healthcare workers should be made aware of this entity to ensure clinical suspicion of CL and investigations needed to confirm CL. The article describes patients seen at a tertiary hospital in Delhi. Aims To establish the utility of the CL Detect Rapid test as a diagnostic tool and the efficacy of Liposomal Amphotericin B (LAmB) for the complete cure of CL patients. Methods Data of patients of CL (n = 16) was retrospectively analysed concerning diagnosis and treatment. Diagnosis rested on histopathology, real-time PCR, and CL Detect Rapid Test. Speciation of the parasite was based on the Internal transcribed spacer-I gene. Patients were treated with LAmB (i.v., 5 mg/kg up to three doses, five days apart). Results A positivity of 81.3% (95%CI, 54.4-96) was observed for CL Detect Rapid test in comparison with 100% (95%CI, 79.4-100.0) for real-time PCR and 43.8% (95%CI, 19.8-70.1) for microscopy/histopathological examination. L. tropica was the infective species in all cases. All the patients treated with LAmB responded to treatment, and 9/10 patients demonstrated complete regression of lesions, while one was lost to follow-up. Limitations It is a retrospective study, and the data includes only confirmed cases of CL at a single centre. Conclusion This study highlights the utility of CL Detect as a promising diagnostic tool and the efficacy of LAmB for the complete cure of CL.

HRM Accuracy and Limitations as a Species Typing Tool for Leishmania Parasites

High Resolution Melting Analysis (HRM) has been pointed out as a suitable alternative method to detect and identify Leishmania species. Herein, we aimed to evaluate the sensitivity, specificity, accuracy, and limitations of a HSP70-HRM protocol both as a diagnostic scheme applied in clinical samples and as a species typing tool for laboratory research and reference services. Our data reveal the pronounced species-typing potential of the HSP70-HRM in DNA from cultured parasites. For clinical samples, however, we advise caution due to parasite load-dependent accuracy. In light of these findings and considering the importance of parasite load determination for clinical and research purposes, we recommend the integration of the presented typing scheme and the previously published Leishmania quantifying approach as combined tools for clinicians, surveillance, and research.

Molecular Diagnosis of Leishmaniasis in Spain: Development and Validation of Ready-To-Use Gel-Form Nested and Real-Time PCRs To Detect Leishmania spp

Leishmaniasis is an endemic parasitic disease in at least 98 countries. In Spain, it is considered a zoonosis caused by Leishmania infantum, with an annual incidence of 0.62 cases/100,000 inhabitants. The predominant clinical manifestations are the cutaneous (CL) and visceral forms (VL), and the diagnosis is performed by parasitological, serological, and molecular tests. At the WHO Collaborating Center for Leishmaniasis (WHOCCLeish), routine diagnostic tests are based on a nested PCR (Ln-PCR), culture, and serological tests. To simplify our PCR protocol, we aimed to develop and validate a ready-to-use nested gel-form PCR (LeishGelPCR) and a duplex real-time PCR (qPCR) that allowed simultaneous detection of Leishmania and mammalian DNA as an internal control (Leish-qPCR). Clinical validation was performed in 200 samples from the WHOCCLeish collection; 92 and 85 out of 94 and 87 samples were positive by LeishGelPCR and Leish-qPCR, respectively, showing a sensitivity of 98% in both approaches. The specificity was 100% for LeishGelPCR and 98% for Leish-qPCR. The limits of detection of both protocols were similar (0.5 and 0.2 parasites/reaction). Parasite loads in VL and CL forms were similar, although high loads were observed when invasive samples were tested. In conclusion, LeishGelPCR and Leish-qPCR showed excellent performance in the diagnosis of leishmaniasis. These new forms of 18S rRNA gene PCR are equivalent to Ln-PCR and can be introduced in the algorithm for CL and VL diagnosis. IMPORTANCE Although the gold standard for diagnosis of leishmaniasis is the microscopic observation of amastigotes, molecular techniques are becoming a cost-efficient alternative. Currently, PCR is a routine resource that is used in many reference microbiology laboratories. In this article, we have described two ways to improve the reproducibility and usability of the molecular detection of Leishmania spp. These new approaches could be introduced even in middle- and low-resource laboratories; one is a ready-to-use gel-form system of a nested PCR and the other is a real-time PCR. We show why molecular diagnosis is the best methodology to confirm a clinical suspicion of leishmaniasis with higher sensitivity than traditional methods, thus facilitating early diagnosis and timely treatment of human leishmaniasis.

Integrating metabolomics and metatranscriptomics to explore the formation pathway of aroma-active volatile phenolics and metabolic profile during industrial radish paocai fermentation

The aroma profile of industrial Sichuan paocai is formed and regulated by complex physiological and biochemical reactions and microbial metabolism, but little is known so far. In this study, we comprehensively analyzed the changes of metabolic profile and gene expression profile, mainly explored the formation pathways of two skeleton aroma-active compounds, 4-ethylphenol and 4-ethylguaiacol, and verified the pathways at multiple levels. The results showed that a total of 136 volatile metabolites and 560 non-volatile metabolites were identified in the whole fermentation process. The types and concentrations of metabolites in paocai were higher than those in brine, and gradually converged with fermentation. Differential analysis of metabolism and transcription levels were both enriched in three pathways: amino acid metabolism, phenylpropanoid metabolism and lipid metabolism. Among them, 4-ethylphenol and 4-ethylguaiacol, the products of the phenylpropanoid metabolism, were converted from p-coumaric acid and ferulic acid in plant cell walls, respectively. Under the action of decarboxylase produced by yeast (such as Debaryomyces Hansenii) and lactic acid bacteria (such as Lactobacillus versmoldensis), intermediate metabolites vinylphenols were produced, and the intermediate metabolites further produce the final products under the action of vinylphenol reductase. The key gene copy number, enzyme activity, and metabolite concentration in the pathways were detected to provide stronger evidence for the formation pathways. This study provided meaningful new insights for the development of aroma-producing enzymes and further guidance for the flavor improvement of industrial paocai.

Laboratory diagnostics for human Leishmania infections: a polymerase chain reaction-focussed review of detection and identification methods

Leishmania infections span a range of clinical syndromes and impact humans from many geographic foci, but primarily the world's poorest regions. Transmitted by the bite of a female sand fly, Leishmania infections are increasing with human movement (due to international travel and war) as well as with shifts in vector habitat (due to climate change). Accurate diagnosis of the 20 or so species of Leishmania that infect humans can lead to the successful treatment of infections and, importantly, their prevention through modelling and intervention programs. A multitude of laboratory techniques for the detection of Leishmania have been developed over the past few decades, and although many have drawbacks, several of them show promise, particularly molecular methods like polymerase chain reaction. This review provides an overview of the methods available to diagnostic laboratories, from traditional techniques to the now-preferred molecular techniques, with an emphasis on polymerase chain reaction-based detection and typing methods.

Characterization of Leishmania spp. Causing Cutaneous Lesions with a Negative Parasitological Diagnosis in Panama

A total of 123 DNA samples from Panamanian patients with cutaneous leishmaniasis (CL) lesions were evaluated. These samples were previously confirmed with CL by a specific KDNA-Viannia PCR but had a negative parasitological diagnosis (Group A). Epidemiological variables, such as age, sex, geographic origin, evolution time, and the number and location of the lesions, were analyzed. No significant differences (p < 0.05) were found when these variables were evaluated against a control panel of 123 CL lesion samples from CL patients with positive parasitological diagnoses (Group B). Of the 123 samples (Group A), 67% (82/123) gave positive results when re-analyzed by PCR-hsp70. An analysis of 69 of these samples via PCR-hsp70-RFLP showed that 59.4% (41/69) of the found restriction patterns corresponded to Leishmania (Viannia) panamensis and 40.6% (28/69) to Leishmania (Viannia) guyanensis. Finally, the sequence and phylogenetic analysis of 32 of the samples confirmed the species in 21 (65.6%, 21/32) samples, originally characterized as L. (V.) panamensis. However, 11 samples (34.4%, 11/32), initially identified via RFLP-Hsp70 as L. (V.) guyanensis, matched the sequence of a genetic variant known as Leishmania sp.1. These results point out the species/genetic variants of Leishmania in the case of CL lesions with an apparently low parasite load.

Novel CRISPR-based detection of Leishmania species

Tegumentary leishmaniasis, a disease caused by protozoan parasites of the genus Leishmania, is a major public health problem in many regions of Latin America. Its diagnosis is difficult given other conditions resembling leishmaniasis lesions and co-occurring in the same endemic areas. A combination of parasitological and molecular methods leads to accurate diagnosis, with the latter being traditionally performed in centralized reference and research laboratories as they require specialized infrastructure and operators. Clustered regularly interspaced short palindromic repeats/CRISPR-associated protein (CRISPR/Cas) systems have recently driven innovative tools for nucleic acid detection that combine high specificity, sensitivity and speed and are readily adaptable for point-of-care testing. Here, we harnessed the CRISPR-Cas12a system for molecular detection of Leishmania spp., emphasizing medically relevant parasite species circulating in Peru and other endemic areas in Latin America, with Leishmania (Viannia) braziliensis being the main etiologic agent of cutaneous and mucosal leishmaniasis. We developed two assays targeting multi-copy targets commonly used in the molecular diagnosis of leishmaniasis: the 18S ribosomal RNA gene (18S rDNA), highly conserved across Leishmania species, and a region of kinetoplast DNA (kDNA) minicircles conserved in the L. (Viannia) subgenus. Our CRISPR-based assays were capable of detecting down to 5 × 10-2 (kDNA) or 5 × 100 (18S rDNA) parasite genome equivalents/reaction with PCR preamplification. The 18S PCR/CRISPR assay achieved pan-Leishmania detection, whereas the kDNA PCR/CRISPR assay was specific for L. (Viannia) detection. No cross-reaction was observed with Trypanosoma cruzi strain Y or human DNA. We evaluated the performance of the assays using 49 clinical samples compared to a kDNA real-time PCR assay as the reference test. The kDNA PCR/CRISPR assay performed equally well as the reference test, with positive and negative percent agreement of 100%. The 18S PCR/CRISPR assay had high positive and negative percent agreement of 82.1% and 100%, respectively. The findings support the potential applicability of the newly developed CRISPR-based molecular tools for first-line diagnosis of Leishmania infections at the genus and L. (Viannia) subgenus levels.

Cutaneous Leishmaniasis: A 2022 Updated Narrative Review into Diagnosis and Management Developments

This review is an update of an earlier narrative review published in 2015 on developments in the clinical management of cutaneous leishmaniasis (CL) including diagnosis, treatment, prevention and control measurements. CL is a vector-borne infection caused by the protozoan parasite Leishmania. The vector is the female sandfly. Globally, CL affects 12 million cases and annually 2 million new cases occur. CL is endemic in almost 100 countries and the total risk population is approximately 350 million people. WHO lists CL an emerging and uncontrolled disease and a neglected tropical disease. Local experience-based evidence remains the mainstay for the management of CL. Whereas intralesional therapeutic options are the first treatment option for most CL patients, those with mucocutaneous and disseminated involvement require a systemic therapeutic approach. Moreover, different Leishmania species can vary in their treatment outcomes. Therefore, species determination is critical for optimal CL clinical management. New DNA techniques allow for relatively easy Leishmania species determination, yet they are not easily implemented in resource-limited settings. There is a desperate need for novel, less toxic, and less painful treatment options, especially for children with CL. Yet, the large and well conducted studies required to provide the necessary evidence are lacking. To further control and potentially eliminate CL, we urgently need to improve vector control, and diagnostics, and we require efficient and safe vaccines. Alas, since CL primarily affects poor people, biotechnical companies dedicate little investment into the research programs that could lead to diagnostic, pharmaceutical, and vaccine innovations.

Anti-mitochondrial Tryparedoxin Peroxidase Monoclonal Antibody-Based Immunohistochemistry for Diagnosis of Cutaneous Leishmaniasis

Cutaneous leishmaniasis (CL) remains a globally spreading public health problem. Among Latin America countries, Brazil has the greatest number of recorded CL cases with several Leishmania species being associated with human cases. Laboratory diagnosis is one of the major challenges to disease control due to the low accuracy of parasitological techniques, the restricted use of molecular techniques, and the importance of differential diagnosis with regard to several dermatological and systemic diseases. In response, we have developed and validated an immunohistochemistry (IHC) technique for CL diagnosis using anti-mTXNPx monoclonal antibody (mAb). Recombinant Leishmania–mTXNPx was produced and used as an immunogen for mAb production through the somatic hybridization technique. The viability of mAb labeling of Leishmania amastigotes was tested by IHC performed with skin biopsies from hamsters experimentally infected with Leishmania amazonensis, Leishmania braziliensis, and Leishmania guyanensis. The enzymes horseradish peroxidase (IHC-HRP) and alkaline phosphatase (IHC-AP), both biotin-free polymer detection systems, were used in the standardization step. The IHC was further validated with skin biopsies from 49 CL patients diagnosed by clinical examination and quantitative real-time polymerase chain reaction and from 37 patients presenting other dermatological infectious diseases. Other parasitological techniques, such as direct examination and culture, were also performed for confirmed CL patients. Histopathology and IHC were performed for all included patients. Overall, the highest sensitivity was observed for IHC-AP (85.7%), followed by IHC-HRP (79.6%), direct examination (77.6%), histopathological examination (HE; 65.3%), and in vitro culture (49%). Only IHC and HE presented specificity over 90% and were able to detect CL patients regardless of parasite burden (odds ratio > 1.94; 95%CI: 0.34–11.23). A significant increase in positivity rates was observed when IHC-AP was combined with direct examination (95.9%) and HE (93.9%). The IHC techniques evaluated in here detected the main Leishmania species causing CL in Brazil and can support diagnostic strategies for controlling this neglected disease, especially if used in combination with other approaches for an integrative laboratorial diagnosis.

Advancement in leishmaniasis diagnosis and therapeutics: An update

Leishmaniasis is regarded as a neglected tropical disease by World Health Organization (WHO) and is ranked next to malaria as the deadliest protozoan disease. The primary causative agents of the disease comprise of diverse leishmanial species sharing clinical features ranging from skin abrasions to lethal infection in the visceral organs. As several Leishmania species are involved in infection, the role of accurate diagnosis becomes pivotal in adding new dimensions to anti-leishmanial therapy. Diagnostic methods must be fast, reliable, easy to perform, highly sensitive, and specific to differentiate among similar parasitic diseases. Herein, we present the conventional and recent approaches impended for the disease diagnosis and their sensitivity, specificity, and clinical application in parasite detection. Furthermore, we have also elaborated various new methods to cure leishmaniasis, which include host-directed therapies, drug repurposing, nanotechnology, and combinational therapy. This review addresses novel techniques and innovations in leishmaniasis, which can aid in unraveling new strategies to fight against the deadly infection.

Diagnostic Efficacy of Recombinase-Polymerase-Amplification Coupled with Lateral Flow Strip Reading in Patients with Cutaneous Leishmaniasis from the Amazonas Rainforest of Perú

Cutaneous leishmaniasis (CL) is highly prevalent in rural and sylvatic regions of Latin America, with an estimated 55,000 annual cases. Diagnosis in resource-limited areas still relies on microscopy of dermal scrapings, while more sensitive methods like PCR are not attainable due to costs and lack of adequate health infrastructure. Isothermal amplification of Leishmania DNA can be performed without sophisticated equipment and training and may become a point of care (POC) test for health care centers with scarce resources. We evaluated the efficacy of recombinase-polymerase-amplification (RPA-LF) to diagnose CL in 226 patients attending a clinic in Puerto Maldonado within the Peruvian Amazon basin. Conventional PCR targeting kinetoplast DNA (kDNA-PCR) was used as the gold standard. Eight of 226 patients were considered true negatives (microscopy, kDNA-PCR, and RPA-LF negative), while RPA-LF resulted positive in 186 of 204 kDNA-PCR positive patients, yielding 91.2% (confidence interval [CI] = 86.5-94.4%) sensitivity and 93% (CI 88.6-95.8%) positive predictive value. There were 14% (32/226) discrepant samples alternating positive and negative results in similar proportions between both tests. Quantitative PCR used to resolve the discrepancies suggested that they occurred in samples with scarce parasite numbers as determined by high cycle threshold (Ct) values (≥32; cutoff 35.5). Microscopy had the lowest sensitivity of all methods (45.4%). Nested real-time PCR performed in 71 samples determined that Leishmania (Viannia) braziliensis was highly prevalent (69/71), and Leishmania (Viannia) lainsoni was present in only two isolates. Results indicated that RPA-LF has POC potential for CL endemic areas, yet further simplification and optimization coupled with field validation will be necessary to confirm its broad applicability.

From infection to vaccination: reviewing the global burden, history of vaccine development, and recurring challenges in global leishmaniasis protection

INTRODUCTION

Leishmaniasis is a major public health problem and the second most lethal parasitic disease in the world due to the lack of effective treatments and vaccines. Even when not lethal, leishmaniasis significantly affects individuals and communities through life-long disabilities, psycho-sociological trauma, poverty, and gender disparity in treatment.

AREAS COVERED

This review discusses the most relevant and recent research available on Pubmed and GoogleScholar highlighting leishmaniasis' global impact, pathogenesis, treatment options, and lack of effective control strategies. An effective vaccine is necessary to prevent morbidity and mortality, lower health care costs, and reduce the economic burden of leishmaniasis for endemic low- and middle-income countries. Since there are several forms of leishmaniasis, a pan-Leishmania vaccine without geographical restrictions is needed. This review also focuses on recent advances and common challenges in developing prophylactic strategies against leishmaniasis.

EXPERT OPINION

Despite advances in pre-clinical vaccine research, approval of a human leishmaniasis vaccine still faces major challenges - including manufacturing of candidate vaccines under Good Manufacturing Practices, developing well-designed clinical trials suitable in endemic countries, and defined correlates of protection. In addition, there is a need to explore Challenge Human Infection Model to avoid large trials because of fluctuating incidence and prevalence of leishmanasis.

Clinical and epidemiological profiles of patients with American cutaneous leishmaniasis from the states of Pernambuco and Amazonas, Brazil

INTRODUCTION:

Brazil has a high number of cases of American cutaneous leishmaniasis (ACL) in the north and northeast regions. Therefore, continuous surveillance of environmental and socioeconomic factors in endemic areas is needed to develop strategic control measures. This study aimed to describe the clinical and epidemiological profiles of patients with ACL.

METHODS:

All patients were from the states of Amazonas and Pernambuco, and examinations were carried out between 2015 and 2018. All patients had a clinical and epidemiological history compatible with ACL after positive diagnostic tests. Information obtained from medical records included gender, employment activity, level of education, age, and number and sites of lesions.

RESULTS:

A total of 213 patients were included, of whom 30.98% were female and 69.02% were male. The main employment activity was agriculture (27.56%). The most common level of education was elementary (62.42%). The average age was approximately 39 years. The majority of the patients presented only with one lesion (54.87%), and legs/feet were the most commonly affected area (48.25%), followed by the arms/hands (44.75%).

CONCLUSIONS:

These data demonstrated that irrespective of the patients’ places of origin, interventions need to be focused on men of economically productive age, in view of the high risk of exposure to the vector in this group. Education activities need to be directed to farmers about the importance of protection against ACL vectors during work. Such information must also be directed to employers as a way of implementing and maintaining appropriate working conditions and stepping up vector control.

Laboratory Diagnosis of Cutaneous and Visceral Leishmaniasis: Current and Future Methods

Leishmaniasis is a neglected tropical disease with two main clinical forms: cutaneous and visceral leishmaniasis. Diagnosis of leishmaniasis is still a challenge, concerning the detection and correct identification of the species of the parasite, mainly in endemic areas where the absence of appropriate resources is still a problem. Most accessible methods for diagnosis, particularly in these areas, do not include the identification of each one of more than 20 species responsible for the disease. Here, we summarize the main methods used for the detection and identification of leishmaniasis that can be performed by demonstration of the parasite in biological samples from the patient through microscopic examination, by in vitro culture or animal inoculation; by molecular methods through the detection of parasite DNA; or by immunological methods through the detection of parasite antigens that may be present in urine or through the detection of specific antibodies against the parasite. Potential new methods that can be applied for laboratory diagnosis of leishmaniasis are also discussed.

Comparison and clinical validation of qPCR assays targeting Leishmania 18S rDNA and HSP70 genes in patients with American Tegumentary Leishmaniasis

Leishmaniasis is a worldwide neglected disease, encompassing asymptomatic infections and different clinical forms, such as American Tegumentary Leishmaniasis (ATL) which is part of the complex of diseases caused by protozoan parasites from Leishmania genus, transmitted by sand fly vectors. As a neglected disease, much effort is still needed in treatment and diagnosis. Currently, ATL diagnosis is mainly made by parasite detection by microscopy. The sensitivity of the method varies, and factors such as collection procedures interfere. Molecular approaches, specially based on Real Time PCR (qPCR) technique, has been widely used to detect Leishmania infection and to quantify parasite load, once it is a simple, rapid and sensitive methodology, capable to detect low parasite concentrations and less prone to variability. Although many studies have been already published addressing the use of this technique, an improvement on these methodologies, including an analytical validation, standardization and data association is demanded. Moreover, a proper validation by the assay by the use of clinical samples is still required. In this sense, the purpose of the present work is to compare the performance of qPCR using two commonly used targets (18S rDNA and HSP70) with an internal control (RNAse P) in multiplex reactions. Additionally, we validated reactions by assaying 88 samples from patients presenting different clinical forms of leishmaniasis (cutaneous, mucosal, recent and old lesions), representing the diversity found in Brazil's Amazon Region. Following the methodology proposed herein, the results indicate the use of both qPCR assays, 18S rDNA and HSP70, to achieve a very good net sensitivity (98.5%) and specificity (100%), performing simultaneous or sequential testing, respectively. With this approach, our main goal is to conclude the first step of a further multicenter study to propose the standardization of detection and quantification of Leishmania.

Duplex qPCR for Leishmania species identification using lesion imprint on filter paper

BACKGROUND

American cutaneous leishmaniasis (ACL) is caused by different Leishmania parasites, which stimulate and direct the immune response against the infection.

OBJECTIVE

To evaluate the TaqMan probe technology applicability to diagnose and identifying of Leishmania spp. related to the ACL etiology.

METHODOLOGY

Through the MEGA 6.0 software, performed an in silico analysis using multiple alignments of Leishmania spp. which were available on GenBank for different genomic targets. The efficiency (e), specificity and detection limit (DL) were calculated for each system, these were associated to compose a duplex-qPCR (DqPCR). The samples of blood, lesion biopsy and lesion imprint on filter paper from patients residing in states of Amazonas (AM) and Pernambuco (PE)-Brazil, (cases and controls) were used to perform the DqPCR technique. The capacity to identify the Leishmania species was determined by comparison with isoenzymes method and sequencing analysis.

RESULTS

Internal Transcribed Spacer 1 (rDNA) was the target selected. Two sets of primers and probes were designed and combined: SVS for subgenus Viannia and LaS for L. (L.) amazonensis. The results were: SVSe = 93.24%, SVS DL = 50 fg/μL; LaSe = 89.3%, LaSLD = 5 fg/μL presented 100% of specificity. In total, 236 individuals participated of the present study, wherein were 101 blood samples, 33 biopsies and 147 lesion imprints. The imprint was the most sensitive sample, showing 83.06% of sensitivity, 86.96% of specificity and substantial agreement between the techniques analysis (k = 0.531; p < 0,001). Regarding the species identification, DqPCR and sequencing/isoenzymes have agreed at 100%, since the infection is caused by a single Leishmania species.

CONCLUSION

The DqPCR technique was applicable in diagnosis and identification of Leishmania spp. (subgenus Viannia and L. amazonensis). Furthermore, the lesion imprint is less invasive, allowing a fewer discomfort and greater acceptance by the patients, in addition of being low cost and easy handling.

Performance of a universal PCR assay to identify different Leishmania species causative of Old World cutaneous leishmaniasis

BACKGROUND

The characterization of Leishmania species is important for clinical management of the diseases and the epidemiological control of the parasite distribution. Most of the published polymerase chain reaction (PCR) amplification methods lack the ability to identify all species complexes, have low performance and usually need post-PCR procedures. There is a need for improving the diagnosis of CL by development of an accurate affordable PCR method to identify all Leishmania species in clinical specimens.

METHODS

We designed an optimized a PCR amplifying the internal transcribed spacer 2 sequence of the ribosomal RNA gene (ITS2) aligned from different strains of CL-causing Leishmania species in the Old World. The performance of the method was evaluated on lesion samples from several CL suspected patients and the limit of detection (LOD) was determined on DNA of promastigotes from reference strains.

RESULTS

The universal PCR enabled simultaneous discrimination of L. major, L. tropica and L. infantum using one primer pair in one reaction. Stained smear microscopy and Novy-MacNeal-Nicolle (NNN) medium culture alone detected 77.27% (17/22) and 72.73% (16/22) of the positive CL samples, respectively. The PCR assay showed 100% sensitivity (22/22) (95% CI: 84.56-100%) and 100% specificity (3/3) (95% CI: 29.24-100%) for species identification on isolates from lesion scraping/exudate and 100% sensitivity (13/13) (95% CI: 75.29-100%) and 100% specificity (11/11) (95% CI: 71.51-100%) for species identification on biopsy samples of CL patients, while being capable to successfully amplify as little as 0.01-0.1 pg of Leishmania DNA from cultured promastigotes.

CONCLUSIONS

We present a validated easy-to-use affordable universal PCR assay to identify the most common Old World Leishmania species causing CL. This PCR assay could be used as a sensitive/specific technique to diagnose CL-causing Leishmania species in clinical samples with high accuracy.

Cutaneous leishmaniasis in the 21st century: from the laboratory to the bedside

PURPOSE OF REVIEW

Despite modern advances in molecular diagnostic tools and a better understanding of its complex pathophysiology, cutaneous leishmaniasis, a neglected tropical disease, remains a major global health problem. Laboratory methods to inform prognosis and treatment are not widely available, the therapeutic options are limited and have significant adverse effects, and emergence of drug resistance is a further complication. New advances in the understanding of the role of Leishmania RNA virus (LRV) as a prognostic factor, speciation methods and antimicrobial resistance testing and their limitations will be discussed.

RECENT FINDINGS

LRV, an intracytoplasmic endosymbiont found mostly in Leishmania spp. associated with more severe disease, appears to play a role in modulating the host immune response and has been associated with treatment failure in some Viannia subgenus species. Proper speciation is an important guide to management. However, recent findings have demonstrated significant heterogeneity of results related to differences in genotyping methods.

SUMMARY

Recognition of the role of LRV in immune modulation and response to treatment along with more accessible tools for its detection to guide management at the bedside should allow a better individualized approach. Improving accessibility and standardization of speciation methods and antimicrobial susceptibility testing should be major goals to improve cutaneous leishmaniasis management in the 21st century.

Sporotrichoid dissemination of cutaneous leishmaniasis possibly triggered by a diagnostic puncture

We present the images of a cutaneous leishmaniasis with sporotrichoid dissemination in a Spanish woman who was living in Bolivia for six months. A diagnostic puncture of the ulcer could have been the trigger for the lymphatic dissemination.

Diagnostic performance of a qPCR for Leishmania on stained cytological specimens and on filter paper impressions obtained from cutaneous lesions suggestive of canine leishmaniosis

BACKGROUND

Detection of Leishmania in cutaneous lesions is possible by visualization of amastigotes. Detection of Leishmania DNA by PCR presents greater sensitivity, and PCR has been used to diagnose cutaneous leishmaniosis in humans using noninvasive clinical specimens.

OBJECTIVES

Study I: to determine if Leishmania DNA could be efficiently extracted and amplified from archived Diff-Quik^® -stained slides of cytological specimens from canine cutaneous lesions. Study II: to evaluate the diagnostic performance of a Leishmania-quantitative (q)PCR on stained cytological specimens and on filter paper impressions (FPI) obtained from cutaneous lesions suggestive of canine leishmaniosis (CanL).

ANIMALS

Samples from cutaneous lesions of 54 dogs.

METHODS AND MATERIALS

Study I: Leishmania-qPCR was performed on 19 glass slides (from nine dogs) with cytologically visible amastigotes. Fifteen slides with no visible amastigotes, obtained from 12 dogs seronegative for Leishmania by ELISA, served as controls. Study II: Leishmania-qPCR was performed on glass slides and FPI from cutaneous lesions compatible with clinical leishmaniosis in 33 dogs.

RESULTS

Study I: all slides with visible amastigotes had positive qPCR, whereas all control slides yielded negative results. Study II: of 13 dogs definitively diagnosed with clinical leishmaniosis, eight had visible amastigotes on cytology, whereas Leishmania-qPCR was positive on 11 glass slides and 13 FPI. Leishmaniosis was ruled out by standard methods in 20 dogs, four of which yielded positive qPCR on FPI and/or glass slides.

CONCLUSIONS AND CLINICAL IMPORTANCE

Leishmania-DNA can be detected efficiently by qPCR from cutaneous cytological specimens and FPI to diagnose Leishmania infection in dogs with cutaneous lesions suggestive of CanL.

Imported cutaneous leishmaniasis: a 13-year experience of a Polish tertiary center

INTRODUCTION

Leishmaniasis is a vector-borne infection endemic in 98 countries. Its cutaneous form (CL) causes skin lesions on exposed parts of the body and may lead to scarring. The numbers of imported cases of CL are increasing in Europe but the incidence of CL importation in Poland is unknown.

MATERIAL AND METHODS

A list of all patients diagnosed with CL at the Department in the years 2005-2017 was obtained. The study presents their data including age, sex, areas visited, purpose of travel, time from the onset of symptoms to correct diagnosis, appearance of lesions, results of impression smears and PCR, and superinfection, if detected, as well as treatment methods and their outcomes.

RESULTS

Altogether, 14 cases of cutaneous leishmaniasis were identified. The study demonstrates an increase in the number of cases of imported CL at our center over the last 5 years. The time to correct diagnosis was long in spite of the fact that the lesions had usually an appearance typical of CL.

CONCLUSIONS

Intensified education of physicians and travelers, as well as improvement in the access to travel medicine services and to the diagnosis and treatment methods appropriate for CL, are needed in our country. In our opinion, surveillance of leishmaniasis should be introduced in Poland.

Real-time PCR applications for diagnosis of leishmaniasis

Leishmaniasis is a vector-borne disease caused by many Leishmania species, which can infect both humans and other mammals. Leishmaniasis is a complex disease, with heterogeneous clinical manifestations ranging from asymptomatic infections to lesions at cutaneous sites (cutaneous leishmaniasis), mucosal sites (mucocutaneous leishmaniasis) or in visceral organs (visceral leishmaniasis), depending on the species and host characteristics. Often, symptoms are inconclusive and leishmaniasis can be confused with other co-endemic diseases. Moreover, co-infections (mainly with HIV in humans) can produce atypical clinical presentations. A correct diagnosis is crucial to apply the appropriate treatment and the use of molecular techniques in diagnosis of leishmaniasis has become increasingly relevant due to their remarkable sensitivity, specificity and possible application to a variety of clinical samples. Among them, real-time PCR (qPCR)-based approaches have become increasingly popular in the last years not only for detection and quantification of Leishmania species but also for species identification. However, despite qPCR-based methods having proven to be very effective in the diagnosis of leishmaniasis, a standardized method does not exist. This review summarizes the qPCR-based methods in the diagnosis of leishmaniasis focusing on the recent developments and applications in this field.

A versatile and sensitive lateral flow immunoassay for the rapid diagnosis of visceral leishmaniasis

Visceral leishmaniasis (VL) is a zoonotic infectious disease with a severe impact on humans and animals. Infection is transmitted by phlebotomine sand flies, and several domestic and wild mammals act as reservoirs for the infection, so the prompt detection of infected hosts is crucial to preventing and controlling the spread of the disease and its transmission to humans. A rapid and portable tool for VL diagnosis based on the lateral flow immunoassay (LFIA) technology is described herein. The device exploits a highly specific chimeric recombinant antigen as the recognition element for capturing anti-leishmanial antibodies, and protein A labelled with gold nanoparticles as the signal reporter. The LFIA shows excellent diagnostic sensitivity (98.4%), specificity (98.9%), and agreement with serological reference methods for diagnosing canine VL. The long-term stability of the LFIA device was confirmed based on six months of storage at room temperature or 4 °C, and the qualitative response of the device was not affected by limited thermal stress. The use of the broadly specific protein A means that the LFIA can be readily adapted to diagnose VL in dogs (the main reservoir for human infection) and other mammals, thus further assisting efforts to control the spread of VL. Graphical abstract A rapid and portable diagnostic tool for visceral leishmaniasis (VL) based on lateral flow immunoassay (LFIA) technology. The presence of anti-leishmanial antibodies is revealed through the binding of these antibodies to a highly specific chimeric antigen. Employing a broadly specific signal reporter (protein A labelled with gold nanoparticles) enables the LFIA to be easily adapted to diagnose VL in different animals.