Use of a clinical tool for screening and diagnosis of cutaneous leishmaniasis in Sri Lanka

Diagnostic Tools for Cutaneous Leishmaniasis Caused by Leishmania donovani: A Narrative Review

Leishmaniasis, a neglected tropical disease, encompasses a spectrum of clinical conditions and poses a significant risk of infection to over one billion people worldwide. Visceral leishmaniasis (VL) in the Indian sub-continent (ISC), where the causative parasite is Leishmania donovani, is targeted for elimination by 2025, with some countries already reaching such targets. Other clinical phenotypes due to the same species could act as a reservoir of parasites and thus pose a challenge to successful control and elimination. Sri Lanka has consistently reported cutaneous leishmaniasis (CL) due to L. donovani as the primary disease presentation over several decades. Similar findings of atypical phenotypes of L. donovani have also been reported from several other countries/regions in the Old World. In this review, we discuss the applicability of different methods in diagnosing CL due to L. donovani and a comprehensive assessment of diagnostic methods spanning clinical, microscopic, molecular, and immunological approaches. By incorporating evidence from Sri Lanka and other regions on L. donovani-related CL, we thoroughly evaluate the accuracy, feasibility, and relevance of these diagnostic tools. We also discuss the challenges and complexities linked to diagnosing CL and review novel approaches and their applicability for detecting CL.

Distinct microbiome profiles and biofilms in Leishmania donovani-driven cutaneous leishmaniasis wounds

The endemic strain of Leishmania donovani in Sri Lanka causes cutaneous leishmaniasis (CL) rather than more common visceral form. We have visualized biofilms and profiled the microbiome of lesions and unaffected skin in thirty-nine CL patients. Twenty-four lesions (61.5%) were biofilm-positive according to fluorescence in situ hybridization. Biopsies of biofilm-positive lesions were dominated by Pseudomonas, class Bacilli and Enterobacteriaceae and distinguished by significantly lower community evenness. Higher relative abundance of a class Bacilli OTU was detected in wound swabs versus contralateral skin. Wound swabs and biopsies had significantly distinct microbiome profiles and lower diversity compared to unaffected skin. Greater abundances of potentially pathogenic organisms were observed in wet ulcers, lesions with high parasite loads and large wounds. In summary, more than half of L. donovani associated CL wounds harboured biofilms and the wounds exhibited a distinct, less diverse, microbiome than unaffected skin.

Adaptation and performance of a mobile application for early detection of cutaneous leishmaniasis

Background

Detection and management of neglected tropical diseases such as cutaneous leishmaniasis present unmet challenges stemming from their prevalence in remote, rural, resource constrained areas having limited access to health services. These challenges are frequently compounded by armed conflict or illicit extractive industries. The use of mobile health technologies has shown promise in such settings, yet data on outcomes in the field remain scarce.

Methods

We adapted a validated prediction rule for the presumptive diagnosis of CL to create a mobile application for use by community health volunteers. We used human-centered design practices and agile development for app iteration. We tested the application in three rural areas where cutaneous leishmaniasis is endemic and an urban setting where patients seek medical attention in the municipality of Tumaco, Colombia. The application was assessed for usability, sensitivity and inter-rater reliability (kappa) when used by community health volunteers (CHV), health workers and a general practitioner, study physician.

Results

The application was readily used and understood. Among 122 screened cases with cutaneous ulcers, sensitivity to detect parasitologically proven CL was >95%. The proportion of participants with parasitologically confirmed CL was high (88%), precluding evaluation of specificity, and driving a high level of crude agreement between the app and parasitological diagnosis. The chance-adjusted agreement (kappa) varied across the components of the risk score. Time to diagnosis was reduced significantly, from 8 to 4 weeks on average when CHV conducted active case detection using the application, compared to passive case detection by health facility-based personnel.

Conclusions

Translating a validated prediction rule to a mHealth technology has shown the potential to improve the capacity of community health workers and healthcare personnel to provide opportune care, and access to health services for underserved populations. These findings support the use of mHealth tools for NTD research and healthcare.

Cutaneous leishmaniasis (CL) and other tropical diseases primarily affect people in developing and underserved parts of the world where healthcare infrastructure, resources and trained personnel are scarce. Smartphones, connected to the internet and running innovative health-applications—"apps"—have shown promise to bridge gaps in access to healthcare in even the most remote areas. Using participatory and human centered-design methods, we developed a mobile application for Android smartphones that supports community health workers to screen potential cases of CL in rural settings. We developed this application using a previously validated clinical prediction rule and tested it with patients, community workers and health workers in the municipality of Tumaco on the Pacific Coast of Colombia. Results from this study showed that the mobile app was easy to use, could detect cutaneous leishmaniasis in over 95% of cases, and reduced the time to diagnosis by half compared to passive case detection dependent on consultation at referral facilities. Overall, this work showed the value of designing health interventions with early engagement of all users, and supports the general use of mobile health applications for neglected tropical disease research and care.

First Evidence from Sri Lanka for Subphenotypic Diversity within L. donovani-Induced Classical Cutaneous Leishmaniasis

Sri Lanka reports a large focus of Leishmania donovani-induced cutaneous leishmaniasis (CL) with CL as the main clinical entity. Two independent, long existed, and clinicoepidemiologically different transmission foci in the northern region (NR) and southern region (SR) were recently reported. Current project is an extension to this previous study. Clinical diversity within a profile of classical cutaneous leishmaniasis (CCL) in a focus of L. donovani-induced CL is described for the first time. Patients with laboratory confirmed CCL (n = 550) from NF and SF were evaluated. Lesions in both foci were found to have all classical developmental stages (small and large nodules, ulcerating nodules, and ulcers) and other identified changes (multiplication, ulceration, and enlargement). Main difference was in the proportions of lesions progressing in to each different stages, proportions of lesion undergoing the main changes, and in timing of these changes during the course of a lesion. Northern focus reported a smaller proportion of lesions showing enlargement and ulceration, and a longer period of time was also required for these changes when compared to same in southern focus. In northern focus, most lesions remained small and nonulcerating and showed a higher tendency to multiply while most lesions reported in southern focus enlarged and ulcerated rapidly and remained single. Current study also evidenced a wider spectrum in the rate and pattern of progression of a skin lesion and high individual variation which could mask these region-based differences. Parasitic, vector-related, or a host etiology is suggested. Slow progressing nonulcerating infections in North may be the result of a well-adopted parasite strain that coevolved with its host for a long period while inducing only a minimal host response. This could be one among many reasons for previously observed silent expansion in northern focus while southern focus remained more confined and stable over time. Small nonprogressive, nondisturbing lesions can play a major role as silent parasite reservoirs in a community. In addition, the laboratory detection rate declined significantly when lesions multiplied and enlarged indicating the need for early laboratory confirmation. Usefulness of identified features in clinical screening and management needs to be considered.

First Serological Study Revealing High Humoral Response and Evidence for Antigenic Heterogeneity in Leishmania donovani Induced CL in Sri Lanka

Posing a threat to the ongoing leishmaniasis elimination efforts in the Indian subcontinent, L. donovani-induced cutaneous leishmaniasis (CL) has been recently reported in many countries. Sri Lanka reports a large focus of human cutaneous leishmaniasis (CL) caused by Leishmania donovani, a usually visceralizing parasite. Enhanced case detection, early treatment, and in-depth understanding of sequalae are required to contain the spread of disease. Visceralizing potential of dermotropic strains has not been fully ruled out. Sri Lankan strains have shown a poor response to established serological assays. The present concern was to develop an in-house serological assay and to determine the seroprevalence of CL for identifying visceralizing potential and its usefulness in enhancing case detection. Crude cell lysate of dermotropic L. donovani promastigotes-based indirect enzyme-linked immunosorbent assay (ELISA) was previously optimized. Assay was evaluated using sera from 200 CL patients, 50 endemic and 50 nonendemic healthy controls, 50 patients with other skin diseases, and 50 patients with other systemic diseases. Seroprevalence and clinicoepidemiological associations were analyzed. Assay was compared with light microscopy (LM) and in vitro culturing (IVC). Cost comparison was carried out. Seroprevalence of CL was 82.0%. The assay had 99.5% specificity, and all healthy controls were negative at 0.189 cut-off. Positive and negative predictive values were 99.4% and 84.7%, respectively. Positivity obtained in ELISA was comparable to LM and higher than that of IVC. Cost per patient was 3.0 USD for both ELISA and LM and 6.0 USD for IVC. Infections occurring in all age groups and both genders demonstrated >75.0% of seropositivity. Patients had lesions with different durations/types/sizes showed >70.0% of seropositivity. Study identified a high seroprevalence of L. donovani-induced CL for the first time, indicating potential for visceralization or transient serological response. This can be used as a second line test in LM-negative CL cases to enhance clinical case detection. Further studies are warranted to examine in-depth correlations, antigen profiles, comparison with other established serological tools, and usefulness in the detection of asymptomatic cases. (National patent LK/P/1/19697).

Prevalidation of an ELISA for Detection of a New Clinical Entity: Leishmania donovani-Induced Cutaneous Leishmaniasis

Human leishmaniasis which is considered a neglected tropical parasitic disease presents in three main clinical forms (i.e., cutaneous leishmaniasis (CL), mucocutaneous leishmaniasis (MCL), and visceral leishmaniasis (VL)) that are mainly determined by its causative species. Leishmania donovani, the most virulent and visceralizing parasite, is increasingly reported to cause CL in many countries in the world. Although CL is generally not considered to evoke a humoral immune response except for a nonrobust and a variable response in minority of cases, VL is associated with a clear strong humoral response. However, humoral response in L. donovani-induced CL has not been well evaluated before. A suitable serology-based assay is an essential primary step in such a study. An indirect enzyme-linked immunosorbent assay (ELISA) based on Leishmania promastigote crude antigen (Ag) was designed and optimized in order to utilize in further serological studies on this new clinical entity. Optimization included quantification of crude Ag, checkerboard titration method for determination of optimal concentrations for coating Ag, human sera and secondary antibody (Ab) with suitable coating buffer, blocking buffer, and incubating temperatures. The selected coating buffer was 0.02 M phosphate buffer, pH 6.8, and the blocking buffer was 2% fetal bovine serum with 0.01 M phosphate-buffered saline. At least 1 μg of crude Ag was required for coating the ELISA plate, while 1 : 1000 serum was used as primary Ab. The optimized concentration of secondary Ab was 1 : 64000 which might be altered according to manufacturer recommendations. The assay specificity was pre-evaluated using sera (n = 20 from each category) from confirmed CL patients and controls (other skin diseases which mimic CL, other systemic diseases that mimic VL, nonendemic healthy controls, and endemic healthy controls). This procedure described an optimization procedure of an ELISA technique for detection of anti-Leishmania antibodies in patients with L. donovani caused CL.

New Strategies and Biomarkers for the Control of Visceral Leishmaniasis

Effective diagnosis and treatment of visceral leishmaniasis, together with the study of vectors and reservoirs, can lead to a better understanding of the parasite transmission dynamics and the development of more efficient control measures. Recent studies have applied new methodologies and biomarkers, and these have contributed to the early and rapid diagnosis of the disease; assessment of success of pharmacological treatments; efficient monitoring of immunosuppressed individuals; and to population screening for field trials of vaccine efficacy. This opinion article proposes an update to the diagnostic tools for visceral leishmaniasis and their rational and combined use to establish the real prevalence of infection or of exposure to Leishmania in endemic areas.

Leishmania donovani Induced Cutaneous Leishmaniasis: An Insight into Atypical Clinical Variants in Sri Lanka

Sri Lanka is a recent focus having Leishmania donovani induced cutaneous leishmaniasis (CL) as the main clinical entity. A separate clinical entity within profile of CL was described in this study. Laboratory confirmed cases of CL (n= 950, 2002-2014) were analysed. Most lesions showed known classical developmental stages of CL (CCL) observed in other CL endemic settings while few cases (13%, 122/950) showed atypical skin manifestations (ACL). Clinical, geographical, and treatment response patterns of ACL were different from those of CCL. ACL was mainly found among males (68.0%), in 21-40 year age group (51.6%), and reported delayed treatment seeking (23.5% vs 16.3% in CCL), more nonclassical onset (lesions other than acne form <1cm sized papules), (12.1 vs 2.7%, P<0.05.), more head and neck lesions (41.5%. vs 27.2%), more large lesions (>4cm), (18.6 vs 9.9%), and poor laboratory positivity rates (65.6% vs 88.2%) when compared to CCL. When compared to lesions reporting a typical onset, lesions reporting nonclassical onset were more likely to develop ACL later on (50.1% vs 10.7%). As compared to lesions on limbs, those on head and neck and trunk were more likely to be ACL (7.0%, 16.3%, and 22.8%, respectively, P<0.05). ACL features were not age or gender dependent. Highest proportion within ACL category (32.8%) and small proportion of CCL (10.1%) originated from less leishmaniasis prevalent areas (other regions) (P<0.05). North reported more ACL than South (15.9% vs 7.4%). A total of 95 CL cases with a significant travel history were further analyzed. Residents of other regions when acquired infection from North or South developed more ACL than residents in North or South (60.9% vs 15.9% and 42.9% vs 7.4% respectively). Patients in other regions when travelled to North developed more ACL than when they travelled to South (60.9%, 42.9%). ACL and CCL required an average of 18 doses over 16.7 months and 10 doses over 12 weeks, respectively, to achieve a complete clinical cure. Underlying host immunological factors, parasite strain variations and regional variations of both could be underlying etiologies. Established independent transmission within less leishmaniasis prevalent regions combined with an unusual clinical picture leading to poor clinical suspicion and low laboratory confirmation rate will pose potential difficulties in early case detection in these highly populated and commercialized areas. This in turn will further facilitate silent and high disease transmission.

Trends in Recently Emerged Leishmania donovani Induced Cutaneous Leishmaniasis, Sri Lanka, for the First 13 Years

Sri Lanka reports a large epidemic of cutaneous leishmaniasis (CL) caused by an atypical L. donovani while regional leishmaniasis elimination drive aims at achieving its targets in 2020. Visceralization, mucotrophism, and CL associated poor treatment response were recently reported. Long-term clinico-epidemiological trends (2001-2013) in this focus were examined for the first time. Both constant and changing features were observed. Sociodemographic patient characteristics that differ significantly from those of country profile, microchanges within CL profile, spatial expansion, constant biannual seasonal variation, and nondependency of clinical profile on age or gender were evident. Classical CL remains the main clinical entity without clinical evidence for subsequent visceralization indicating presence of parasite strain variation. These observations make a scientific platform for disease control preferably timed based on seasonal variation and highlights the importance of periodic and continued surveillance of clinic-epidemiological and other characteristics.

Evidence for Seroprevalence in Human Localized Cutaneous Leishmaniasis Caused by Leishmania donovani in Sri Lanka

Visceral leishmaniasis (VL) is considered as a major health threat in the Indian subcontinent. Leishmania donovani, a usually visceralizing species, causes cutaneous leishmaniasis (CL) in Sri Lanka. However, visceralizing potential of the local L. donovani is not yet fully understood. This project studied the seroprevalence of local CL by using an in-house ELISA. An IgG-based ELISA using crude Leishmania antigen (Ag) was developed and validated. A total of 50 laboratory confirmed cases of locally acquired CL were examined using the newly developed ELISA. According to the optimized ELISA, seroprevalence of anti-Leishmania IgG antibodies in the study group was 34.0% (n = 17/50). Majority of seropositive individuals were males (n = 13/17), representing 76%. Nearly half of the seropositive individuals were young adults (20–40 years, n = 9/17, 53%). Higher proportions of single lesions, large lesions, and nodular lesions were associated with a seroconversion. A proportion of local L. donovani infections leading to CL have the ability to raise an antibody response in the host. This may indicate early systemic involvement as one possibility. Study of a large number of patients with adequate follow-up would be useful.

Emergence of visceral leishmaniasis in Sri Lanka: a newly established health threat

BACKGROUND

Sri Lanka is a new focus of human cutaneous leishmaniasis caused by a genetic variant of usually visceralizing parasite Leishmania donovani. Over 3000 cases have been reported to our institution alone, during the past two decades. Recent emergence of visceral leishmaniasis is of concern.

METHODS

Patients suspected of having visceral leishmaniasis (n = 120) fulfilling at least two of six criteria (fever > 2 weeks, weight loss, tiredness affecting daily functions, splenomegaly, hepatomegaly and anemia) were studied using clinic-epidemiological, immunological and haematological parameters. Seven cases (four progressive, treated (group A) and 3 non- progressive, potentially asymptomatic and observed (group B) were identified. Clinical cases were treated with systemic sodium stibogluconate or amphotericin B and all were followed up at the leishmaniasis clinic of University of Colombo for 3 years with one case followed up for 9 years.

RESULTS

All treated cases responded well to anti leishmanial treatment. Relapses were not noticed. Clinical features subsided in all non-progressive cases and did not develop suggestive clinical features or change of laboratory parameters. Visceral leishmaniasis cases have been originated from different districts within the country. Majority had a travel history to identified local foci of cutaneous leishmaniasis.

CONCLUSION

Visceral leishmaniasis is recognized as an emerging health threat in Sri Lanka. At least a proportion of locally identified strains of L. donovani possess the ability to visceralize. Apparent anti leishmanial sensitivity is encouraging. Timely efforts in disease containment will be important in which accurate understanding of transmission characteristics, increased professional and community awareness, improved diagnostics and availability of appropriate treatment regimens.

Arginase activity in pathogenic and non-pathogenic species of Leishmania parasites

Proliferation of Leishmania (L.) parasites depends on polyamine availability, which can be generated by the L-arginine catabolism and the enzymatic activity of arginase (ARG) of the parasites and of the mammalian hosts. In the present study, we characterized and compared the arginase (arg) genes from pathogenic L. major and L. tropica and from non-pathogenic L. tarentolae. We quantified the level of the ARG activity in promastigotes and macrophages infected with pathogenic L. major and L. tropica and non-pathogenic L. tarentolae amastigotes. The ARG's amino acid sequences of the pathogenic and non-pathogenic Leishmania demonstrated virtually 98.6% and 88% identities with the reference L. major Friedlin ARG. Higher ARG activity was observed in all pathogenic promastigotes as compared to non-pathogenic L. tarentolae. In vitro infection of human macrophage cell line (THP1) with pathogenic and non-pathogenic Leishmania spp. resulted in increased ARG activities in the infected macrophages. The ARG activities present in vivo were assessed in susceptible BALB/c and resistant C57BL/6 mice infected with L. major, L. tropica and L. tarentolae. We demonstrated that during the development of the infection, ARG is induced in both strains of mice infected with pathogenic Leishmania. However, in L. major infected BALB/c mice, the induction of ARG and parasite load increased simultaneously according to the time course of infection, whereas in C57BL/6 mice, the enzyme is upregulated solely during the period of footpad swelling. In L. tropica infected mice, the footpads' swellings were slow to develop and demonstrated minimal cutaneous pathology and ARG activity. In contrast, ARG activity was undetectable in mice inoculated with the non-pathogenic L. tarentolae. Our data suggest that infection by Leishmania parasites can increase ARG activity of the host and provides essential polyamines for parasite salvage and its replication. Moreover, the ARG of Leishmania is vital for parasite proliferation and required for infection in mice. ARG activity can be used as one of the main marker of the disease severity.

Polymerase chain reaction detection of Leishmania DNA in skin biopsy samples in Sri Lanka where the causative agent of cutaneous leishmaniasis is Leishmania donovani

Leishmania donovani is the known causative agent of both cutaneous (CL) and visceral leishmaniasis in Sri Lanka. CL is considered to be under-reported partly due to relatively poor sensitivity and specificity of microscopic diagnosis. We compared robustness of three previously described polymerase chain reaction (PCR) based methods to detectLeishmania DNA in 38 punch biopsy samples from patients presented with suspected lesions in 2010. Both, Leishmaniagenus-specific JW11/JW12 KDNA and LITSR/L5.8S internal transcribed spacer (ITS)1 PCR assays detected 92% (35/38) of the samples whereas a KDNA assay specific forL. donovani (LdF/LdR) detected only 71% (27/38) of samples. All positive samples showed a L. donovani banding pattern upon HaeIII ITS1 PCR-restriction fragment length polymorphism analysis. PCR assay specificity was evaluated in samples containing Mycobacterium tuberculosis, Mycobacterium leprae, and human DNA, and there was no cross-amplification in JW11/JW12 and LITSR/L5.8S PCR assays. The LdF/LdR PCR assay did not amplify M. leprae or human DNA although 500 bp and 700 bp bands were observed in M. tuberculosis samples. In conclusion, it was successfully shown in this study that it is possible to diagnose Sri Lankan CL with high accuracy, to genus and species identification, using Leishmania DNA PCR assays.

Characterisation of cutaneous leishmaniasis in Matara district, southern Sri Lanka: evidence for case clustering

Leishmaniasis is a neglected tropical disease transmitted by Phlebotomus spp. sand flies. Cutaneous leishmaniasis (CL) in Sri Lanka is caused by Leishmania donovani. Transmission patterns are different in Southern and Northern Sri Lanka. Current study examined the prevalence, risk factors and distribution of CL in Matara District, Southern Sri Lanka. Total of 2260 individuals from four District Secretariat divisions (DSDs) were screened by house to house surveys using an interviewer administered questionnaire. The study population had an age range of 1-90 years (median  =  43  ±  17.31), low monthly income ( < 20 000 LKR, 52.8%) and a male to female ratio of 1 : 2. Thirty eight patients were diagnosed by light microscopy, culture and/or PCR with a disease prevalence of 1.68%. Spatial mapping provided evidence for significant case clustering, which tended to be more prominent with proximity to forest areas. The risk factors identified were un-plastered brick walls, absence or low usage of protective measures against insect bites, low income and excessive time (>4 hours/day) spent outdoors. However, exposure of limbs while outdoors, unawareness about the disease, type of occupation, common water source as the mode of water supply and presence of animal shelters within 200 m were not associated with the risk of acquiring the disease. Peri-domestic transmission is likely to contribute to the observed case clustering with all age groups at risk of acquiring the infection. Human behavioural habits coinciding with that of the vector, sand fly are likely to enable host-vector contact promoting its spread. Appropriate vector control measures, improvement of housing conditions, public education regarding preventive measures are required to contain the spread of disease.