Nested PCR assay for detection of Leishmania donovani in slit aspirates from post-kala-azar dermal Leishmaniasis Lesions

Post kala-azar dermal leishmaniasis in the Indian sub-continent: challenges and strategies for elimination

Visceral leishmaniasis (VL) is a severe and often fatal form of leishmaniasis caused by Leishmania donovani in the Indian sub-continent. Post Kala-azar Dermal Leishmaniasis (PKDL) is a late cutaneous manifestation of VL, typically occurring after apparent cure of VL, but sometimes even without a prior history of VL in India. PKDL serves as a significant yet neglected reservoir of infection and plays a crucial role in the transmission of the disease, posing a serious threat to the VL elimination program in the Indian sub-continent. Therefore, the eradication of PKDL should be a priority within the current VL elimination program aimed at achieving a goal of less than 1 case per 10,000 in the population at the district or sub-district levels of VL endemic areas. To accomplish this, a comprehensive understanding of the pathogenesis of PKDL is essential, as well as developing strategies for disease management. This review provides an overview of the current status of diagnosis and treatment options for PKDL, highlighting our current knowledge of the immune responses underlying disease development and progression. Additionally, the review discusses the impact of PKDL on elimination programs and propose strategies to overcome this challenge and achieve the goal of elimination. By addressing the diagnostic and therapeutic gaps, optimizing surveillance and control measures, and implementing effective intervention strategies, it is possible to mitigate the burden of PKDL and facilitate the successful elimination of VL in the Indian sub-continent.

Developing, Modifying, and Validating a TaqMan Real-Time PCR Technique for Accurate Identification of Leishmania Parasites Causing Most Leishmaniasis in Iran

Many laboratory methods are used to diagnose leishmaniasis because it is characterized by varied symptoms and caused by different Leishmania species. A quantitative real-time PCR method based on a TaqMan probe was developed and modified for accurate identification of human cutaneous leishmaniasis (caused by Leishmania major or Leishmania tropica) from endemic areas of Iran. Two gene regions of amino acid permease 3 (AAP3) and cytochrome oxidase II (COII) were considered. Six new sets of species-specific primers and probes were designed. A total of 123 samples were examined and employed to evaluate and validate real-time PCR. According to parasitic load of the genesig^®Leishmania Advanced Standard Kit, a serial dilution of purified plasmid (2–2×10⁷ copies/reaction) was prepared under the same conditions for both genes. Specific primers and probes were able to detect three and six parasite copies in AAP3 and COII genes, respectively, and were able to detect three copies of parasites for L. major and L. tropica. The sensitivities of the reference kit and our method were 98.7 and 98.1%, respectively, and specificity was 100% for detecting parasite genomes in all assays. Designed primers and probes performed well in terms of efficiency and regression coefficient. For AAP3 and COII genes, respectively, the linear log range was 7 and the correlation coefficient (R²) was 0.749 and 0.996 for the reference kit using the standard generated curve and 0.98 and 0.96 with serial dilutions of parasite DNA. This research detected L. major and L. tropica definitely and opens the horizon for the other scientists in the multiplex reactions in designing and optimization of the conditions in silico and in vivo.

Molecular Tracking of the Leishmania Parasite

With the Visceral Leishmaniasis/Kala-azar Elimination Program in South Asia in its consolidation phase, the focus is mainly on case detection, vector control, and identifying potential sources of infection. Accordingly, emphasis is presently on curbing transmission, which is potentially achievable by identification and elimination of potential reservoirs. The strongest contenders for being the disease reservoir are cases of Post Kala-azar Dermal Leishmaniasis (PKDL) which occurs in a minor proportion of individuals apparently cured of Visceral Leishmaniasis (VL). The demonstration of parasites in tissue aspirates despite being a risky and invasive process is the gold standard for diagnosis of VL, but is now being replaced by serological tests e.g., rK39 strip test and direct agglutination test. However, these antibody based tests are limited in their ability to diagnose relapses, detect cases of PKDL, and monitor effectiveness of treatment. Accordingly, detection of antigen or nucleic acids by polymerase chain reaction has been successfully applied for monitoring of parasite kinetics. This review article provides updated information on recent developments regarding the available antibody or antigen/nucleic acid based biomarkers for longitudinal monitoring of patients with VL or PKDL and emphasizes the need for availability of studies pertaining to quantification of treatment response or relapse.

Serosurvey and molecular detection of the main zoonotic parasites carried by commensal Rattus norvegicus population in Tehran, Iran

Background

Rattus norvegicus are reservoirs for transmission of various zoonotic parasites, and they have become a threat to public health worldwide. Given the large number and the significant presence of R. norvegicus throughout the city of Tehran, this study aims to assess the frequency of zoonotic parasites carried by commensal rodents wandering in Tehran, Iran. The study considered the north, south, west, east, and center regions of Tehran for the purposes of this study. The serological tests were applied in order to detect effective antibodies against Trichomonas vaginalis (T. vaginalis), Babesia spp., and Cryptosporidium spp. using a commercial qualitative rat ELISA kit. The frequency of Toxoplasma gondii (T. gondii) was surveyed by using the conventional PCR method. Furthermore, nested PCR was employed to detect the presence of Giardia spp. and Leishmania spp. in commensal R. norvegicus dispersed in Tehran.

Results

Approximately, 76% of the 100 R. norvegicus tested were infected with at least one zoonotic parasite, indicating the significant frequency of parasites within the study areas. Seroreactivity against T. vaginalis, Babesia spp., and Cryptosporidium spp. was detected in 5%, 0%, and 1% of the R. norvegicus tested, respectively. T. gondii DNA was detected in 32 out of 100 (32%) R. norvegicus. In addition, Leishmania spp. and Giardia spp. DNA were found in 18 out of 100 (18%) and 76 out of 100 (76%) R. norvegicus investigated, respectively. T. vaginalis with 15% and T. gondii with 70% had the highest frequency of parasites among the R. norvegicus collected from the western and northeastern regions of Tehran, respectively. Moreover, Giardia spp. with 95% and Leishmania spp. with 30% had the highest frequency in the east and center districts, respectively.

Conclusion

The findings showed a wide geographical dissemination of Giardia spp., Toxoplasma gondii, and Leishmania spp. in R. norvegicus within five districts of Tehran. In contrast, other parasites such as Cryptosporidium spp. infection were rarely detected in Rattus populations. No evidence for the circulation of Babesia spp. was found in this study.

Post kala-azar dermal leishmaniasis: A threat to elimination program

Leishmaniasis remains a public health concern around the world that primarily affects poor folks of the developing world spanning across 98 countries with mortality of 0.2 million to 0.4 million annually. Post kala-azar dermal leishmaniasis (PKDL) is the late skin manifestation of visceral leishmaniasis (VL). It has been reported that about 2.5% to 20% of patients recovered from VL develop PKDL having stilted macular or nodular lesions with parasites. In the Indian subcontinent (ISC), it manifests a few months after recovery from VL, though in Africa it can occur simultaneously with VL or a little later. New cases of PKDL are also observed without prior VL in the ISC. These individuals with PKDL represent an important but largely neglected reservoir of infection that perpetuates anthroponotic Leishmania donovani transmission in the ISC and can jeopardize the VL elimination program as these cases can infect the sand flies and spread the endemic. Therefore, it becomes imperative to eradicate PKDL as a part of the VL elimination program. With the limited treatment options besides little knowledge on PKDL, this review stands out in focusing on different aspects that should be dealt for sustained VL elimination.

The usefulness of trained field workers in diagnosis of post-kala-azar dermal leishmaniasis (PKDL) and clinico-epidemiological profile in highly endemic areas of Bihar

BACKGROUND

Surveillance of post-kala-azar dermal leishmaniasis (PKDL) is critical to the elimination of visceral leishmaniasis (VL). In this study we assessed the feasibility of using trained field workers for detecting suspected PKDL cases.

METHODS

A cross-sectional study using a multistage sampling technique was conducted in the Araria district of Bihar. Trained field workers were utilized for identification of suspected PKDL case.

RESULTS

We investigated 57 099 individuals from 11 300 households. The trained field workers were useful in identifying 107 (18%) probable PKDL cases. The calculated PKDL prevalences were 18.7/10 000 and 9.7/10 000 for probable and confirmed PKDL cases, respectively. The median duration of onset of PKDL was 23 months (interquartile range 16.5-56.5). The younger age group developed PKDL significantly more often compared with the older age group (p=0.007). Of the 107 patients, 25 (55.5%) were positive by microscopy of slit skin smear and 42 (93.3%) by polymerase chain reaction. Of 45 patients, 33 (73%) PKDL cases were cured after full treatment. The risk of not being cured with incomplete treatment was three times higher than with complete treatment (relative risk 3.12 [95% confidence interval 1.23 to 8.67], p=0.004).

CONCLUSIONS

We conclude that the prevalence of PKDL is high and the use of trained field workers may be feasible to actively detect PKDL cases in VL-endemic areas of Bihar, India.

Impact of sequelae of visceral leishmaniasis and their contribution to ongoing transmission of Leishmania donovani

Visceral leishmaniasis (VL) in the Old World is caused by infection with Leishmania donovani. Although the numbers of new reported cases of VL in Africa have been relatively stable for several years, the low numbers currently reported on the Indian subcontinent suggest a positive impact of new treatments and intervention strategies. In both regions, however, VL relapse and post-kala-azar dermal leishmaniasis (PKDL) maintain infectious reservoirs and therefore present a threat to control programs. In this review, we outline the evolving appreciation of PKDL as an impactful disease in its own right and discuss the various diagnostic methods that can be applied for the detection and characterization of PKDL cases. We also highlight the data that indicate the potential, and likely contribution, of PKDL cases to ongoing transmission of L. donovani.

Loop-mediated isothermal amplification (LAMP): An advanced molecular point-of-care technique for the detection of Leishmania infection

Leishmaniasis, caused by protozoan parasites of the Leishmania genus, represents an important health problem in many regions of the world. Lack of effective point-of-care (POC) diagnostic tests applicable in resources-limited endemic areas is a critical barrier to effective treatment and control of leishmaniasis. The development of the loop-mediated isothermal amplification (LAMP) assay has provided a new tool towards the development of a POC diagnostic test based on the amplification of pathogen DNA. LAMP does not require a thermocycler, is relatively inexpensive, and is simple to perform with high amplification sensitivity and specificity. In this review, we discuss the current technical developments, applications, diagnostic performance, challenges, and future of LAMP for molecular diagnosis and surveillance of Leishmania parasites. Studies employing the LAMP assay to diagnose human leishmaniasis have reported sensitivities of 80% to 100% and specificities of 94% to 100%. These observations suggest that LAMP offers a good molecular POC technique for the diagnosis of leishmaniasis and is also readily applicable to screening at-risk populations and vector sand flies for Leishmania infection in endemic areas.

Biomarkers in Post-kala-azar Dermal Leishmaniasis

Post-kala-azar dermal leishmaniasis (PKDL) follows visceral leishmaniasis (VL, kala-azar) in 10–60% of cases. It is characterized by an asymptomatic skin rash, usually starting in the face and consisting of macules, papules, or nodules. Diagnosis is difficult in the field and is often made clinically. There is an extensive differential diagnosis, and parasitological confirmation is preferred particularly when drug treatment is considered. The response to treatment is difficult to assess as this may be slow and lesions take long to heal, thus possibly exposing patients unnecessarily to prolonged drug treatment. Biomarkers are needed; these may be parasitological (from microscopy, PCR), serological (from blood, or from the lesion), immunological (from blood, tissue), pathological (from cytology in a smear, histology in a biopsy), repeated clinical assessment (grading, photography), or combinations. In this paper, we will review evidence for currently used biomarkers and discuss promising developments.

Validation of SYBR green I based closed tube loop mediated isothermal amplification (LAMP) assay and simplified direct-blood-lysis (DBL)-LAMP assay for diagnosis of visceral leishmaniasis (VL)

Background

The World Health Organization has targeted elimination of visceral leishmaniasis (VL) in the Indian subcontinent (ISC) by 2020. Despite distinctive decline seen in the number of VL cases in ISC, there is still a quest for development of a diagnostic test which has the utility for detection of active infection and relapse cases and as a test of cure. The present study validated the sensitivity and specificity of SYBR Green I based closed tube LAMP assay reported by us for diagnosis of VL.

Methodology

The validation study was carried out at two endemic sites in India, located at Rajendra Memorial Research Institute of Medical Sciences (RMRIMS), Patna and Institute of Medical Sciences (IMS), Banaras Hindu University (BHU), Varanasi. Standard operating protocols were provided at the two sites for applying LAMP assay on confirmed VL cases. The diagnostic accuracy of LAMP assay was evaluated by Receiver operator curve (ROC) analysis. Furthermore, a simplified LAMP assay based on direct blood lysis, DBL-LAMP, was developed and verified for its diagnostic accuracy.

Principal findings

A total of 267 eligible participants were included in the study which comprised of 179 VL cases and 88 controls. Sensitivity and specificity of the LAMP assay were 98.32% (95% C.I– 95.2–99.7%) and 96.59% (95% C.I.-90.4–99.3%), respectively. ROC curve analysis depicted no significant difference between area under curve (AUC_ROC) for LAMP assay and rK39 RDT, indicative of LAMP as an excellent diagnostic test. DBL-LAMP assay, performed on 67 VL and 100 control samples, yielded a sensitivity of 93.05% (95% C.I- 84.75–97%) and specificity of 100% (95% C.I.- 96.30–100%).

Conclusions/Significance

The validated closed tube LAMP for diagnosis of VL will provide impetus to the ongoing VL elimination programme in ISC. The assay based on direct blood lysis promotes its scope for application in field settings by further reducing time and cost.

Definitive diagnosis of visceral leishmaniasis(VL) by demonstration of amastigotes by microscopy is invasive and risky. Serology based diagnosis using rK39 rapid diagnostic test(RDT) has excellent sensitivity of~97% when combined with clinical symptoms but is inconclusive for detection of active infection and relapses due to persistence of anti-leishmanial antibodies. The developed SYBR Green I based closed tube LAMP assay overcomes these constraints and further, direct blood lysis (DBL)-LAMP, makes it more suitable for field application. The study involved validation of LAMP assay at two endemic sites in India, on a total of 179 VL patients confirmed by rK39 RDT and/ or microscopy and 88 controls. The assay was highly sensitive (98.32%) and specific (96.59%). Further, DBL-LAMP assay yielded a sensitivity and specificity of 93.05% and 100%, respectively. In conclusion, the study has validated the field potential of LAMP assay for diagnosis of VL which will provide momentum to ongoing VL elimination in the Indian subcontinent (ISC).

Evaluation of Real-time PCR for Diagnosis of Post-Kala-azar Dermal Leishmaniasis in Endemic Foci of Bangladesh

Background

Post-kala-azar dermal leishmaniasis (PKDL) is a sequel to visceral leishmaniasis (VL), which is found in VL-endemic countries including Bangladesh. Because of these enigmatic cases, the success of the National Kala-azar Elimination Program is under threat. To date, diagnostic methods for PKDL cases in endemic regions have been limited to clinical examination and rK39 test or microscopy, and a suitable and accurate alternative method is needed. In this study, we investigated the application of real-time polymerase chain reaction (PCR) as a potential method for diagnosis of PKDL in comparison with microscopy.

Methods

Ninety-one suspected macular PKDL cases from Mymensingh district, Bangladesh, were enrolled in the study after diagnosis by clinical examination and an rK39 strip test. All of them responded after completion of the treatment with miltefosine. During enrollment, a skin biopsy was done for each patient, and both microscopy and real-time PCR were performed for detection and quantification of Leishmania donovan body (LDB) and LD DNA, respectively.

Results

Real-time PCR detected 83 cases among all suspected PKDL patients, with an encouraging sensitivity of 91.2% (83.4%–96.1%), whereas microscopy showed 50.6% (39.9%–61.2%) sensitivity. Among all suspected PKDL cases, 42 cases were positive in both microscopy and qPCR, whereas 41 cases were detected as positive through qPCR only.

Conclusions

This study provides evidence that real-time PCR is a promising tool for diagnosis of PKDL in endemic regions. In addition to diagnosis, the quantitative ability of this method could be further exploited for after-treatment prognosis and cure assessment of PKDL cases.

Real-time PCR in detection and quantitation of Leishmania donovani for the diagnosis of Visceral Leishmaniasis patients and the monitoring of their response to treatment

Sustained elimination of Visceral Leishmaniasis (VL) requires the reduction and control of parasite reservoirs to minimize the transmission of Leishmania donovani infection. A simple, reproducible and definitive diagnostic procedure is therefore indispensable for the early and accurate detection of parasites in VL, Relapsed VL (RVL) and Post Kala-azar Dermal Leishmaniasis (PKDL) patients, all of whom are potential reservoirs of Leishmania parasites. To overcome the limitations of current diagnostic approaches, a novel quantitative real-time polymerase chain reaction (qPCR) method based on Taqman chemistry was devised for the detection and quantification of L. donovani in blood and skin. The diagnostic efficacy was evaluated using archived peripheral blood buffy coat DNA from 40 VL, 40 PKDL, 10 RVL, 20 cured VL, and 40 cured PKDL along with 10 tuberculosis (TB) cases and 80 healthy endemic controls. Results were compared to those obtained using a Leishmania-specific nested PCR (Ln-PCR). The real time PCR assay was 100% (95% CI, 91.19-100%) sensitive in detecting parasite genomes in VL and RVL samples and 85.0% (95% CI, 70.16-94.29%) sensitive for PKDL samples. In contrast, the sensitivity of Ln-PCR was 77.5% (95% CI, 61.55-89.16%) for VL samples, 100% (95%CI, 69.15-100%) for RVL samples, and 52.5% (95% CI, 36.13-68.49%) for PKDL samples. There was significant discordance between the two methods with the overall sensitivity of the qPCR assay being considerably higher than Ln-PCR. None of the assay detected L. donovani DNA in buffy coats from cured VL cases, and reduced infectious burdens were demonstrated in cured PKDL cases who remained positive in 7.5% (3/40) and 2.5% (1/40) cases by real-time PCR and Ln-PCR, respectively. Both assays were 100% (95% CI, 95.98-100) specific with no positive signals in either endemic healthy control or TB samples. The real time PCR assay we developed offers a molecular tool for accurate detection of circulating L. donovani parasites in VL, PKDL and RVL patients, as well as being capable of assessing response to treatment. As such, this real time PCR assay represents an important contribution in efforts to eliminate VL.

Serological and Molecular Analysis of Leishmania Infection in Healthy Individuals from Two Districts of West Bengal, India, Endemic for Visceral Leishmaniasis

AbstractSeveral epidemiological studies have indicated the presence of asymptomatic infections with Leishmania donovani in the Indian subcontinent, where parasite transmission is considered anthroponotic. In India, such asymptomatic Leishmania cases have been identified in the state of Bihar. We explored here, the presence of asymptomatic Leishmania infection among healthy individuals living in two districts in the state of West Bengal, India, using serological and molecular tests. Blood samples of 246 healthy individuals were collected from nine villages of Malda and Murshidabad districts in West Bengal, considered endemic for visceral leishmaniasis (VL). Real-time quantitative polymerase chain reaction (qPCR) was performed for the quantification of parasite load in the blood. In addition, two serological tests were carried out to demonstrate anti-Leishmania antibodies: rK39 strip test and anti-total soluble Leishmania antigen IgG using enzyme-linked immunosorbent assay method. Nearly one-fifth (53/246) of the screened population was positive in qPCR as against 10.97% (27/246) positive in rK39 strip test. A range of parasite load was observed in the blood of identified asymptomatic Leishmania cases with a median value of 7.7 parasites/mL (range = 1-65). There was poor agreement between qPCR and serological tests (κ = 0.089, P = 0.13), and 29.62% and 20.54% of the population were qPCR positive in seropositive and seronegative groups, respectively. Combined molecular and serological tests enhanced the capacity to detect asymptomatic Leishmania infection in healthy individuals residing in the endemic areas of VL. A significant proportion of asymptomatic Leishmania individuals was detected in the examined endemic regions of West Bengal that might play a role in promoting VL transmission.

Development of a rapid loop-mediated isothermal amplification assay for diagnosis and assessment of cure of Leishmania infection

Background

Leishmaniasis is a spectrum of diseases with great relevance to public health. Conventional diagnostic methods are time consuming, needing trained personnel. A robust, rapid and cost effective diagnostic test is warranted for on-time diagnosis and field application.

Methods

We have developed a loop mediated isothermal amplification (LAMP) assay with primers (n = 6) based on Leishmania donovani kDNA for detection of Leishmania infection, using a closed tube to prevent cross-contamination. The assay was used to detect Leishmania infection in biological samples obtained from patients of visceral leishmaniasis (VL), post kala-azar dermal leishmaniasis (PKDL) and cutaneous leishmaniasis (CL).

Results

The assay was positive for L. donovani, L. tropica and L. major parasites, with the highest sensitivity towards L. donovani (1 fg DNA). The high sensitivity of the assay for detection of L. donovani was reflected in its ability to detect parasite DNA within 30 min of amplification time with a threshold detection limit of ≥25 copies per reaction. The assay detected parasite in 64 of 66 VL blood samples (sensitivity, 96.9%; 95% CI: 89.6-99.2%), 15 of 15 VL bone marrow aspirate samples (sensitivity, 100%; 95% CI:79.6-100%), 65 of 67 PKDL tissue biopsy samples (sensitivity, 97%; 95% CI:89.7-99.2%). The assay was evaluated in a few cases of CL wherein it was found positive in 8 of 10 tissue biopsies (sensitivity, 80%; 95% CI: 49-94.3%). The assay was negative in all control blood (n = 76) and tissue biopsy (n = 24) samples (specificity, 100%; 95% CI: 96.3-100%). Further, the assay was evaluated for its utility in assessment of cure in treated VL and PKDL patients. The assay detected parasite DNA in 2 of 20VL blood samples and 2 of 21 PKDL tissue samples. Out of 4 cases that were positive for parasite DNA at post treatment stage, 2 patients (1VL and 1 PKDL) returned with relapse.

Conclusions

The study demonstrated a Leishmania genus specific closed tube LAMP assay for reliable and rapid molecular diagnosis of VL and PKDL with potential for application in assessment of cure.

PKDL--A Silent Parasite Pool for Transmission of Leishmaniasis in Kala-azar Endemic Areas of Malda District, West Bengal, India

Post Kala-azar Dermal Leishmaniasis (PKDL) is a chronic but not life-threatening disease; patients generally do not demand treatment, deserve much more attention because PKDL is highly relevant in the context of Visceral Leishmaniasis (VL) elimination. There is no standard guideline for diagnosis and treatment for PKDL. A species-specific PCR on slit skin smear demonstrated a sensitivity of 93.8%, but it has not been applied for routine diagnostic purpose. The study was conducted to determine the actual disease burden in an endemic area of Malda district, West Bengal, comparison of the three diagnostic tools for PKDL case detection and pattern of lesion regression after treatment. The prevalence of PKDL was determined by active surveillance and confirmed by PCR based diagnosis. Patients were treated with either sodium stibogluconate (SSG) or oral miltefosine and followed up for two years to observe lesion regression period. Twenty six PKDL cases were detected with a prevalence rate of 27.5% among the antileishmanial antibody positive cases. Among three diagnostic methods used, PCR is highly sensitive (88.46%) for case confirmation. In majority of the cases skin lesions persisted after treatment completion which gradually disappeared during 6–12 months post treatment period. Reappearance of lesions noted in two cases after 1.5 years of miltefosine treatment. A significant number of PKDL patients would remain undiagnosed without active mass surveys. Such surveys are required in other endemic areas to attain the ultimate goal of eliminating Kala-azar. PCR-based method is helpful in confirming diagnosis of PKDL, referral laboratory at district or state level can achieve it. So a well-designed study with higher number of samples is essential to establish when/whether PKDL patients are free from parasite after treatment and to determine which PKDL patients need treatment for longer period.

A significant number of PKDL patients have been detected in the endemic areas of Malda who would remain undiagnosed without active mass surveys. Such active survey is required in other endemic areas of the country to attain the ultimate goal of eliminating Kala-azar from this part of the world by reducing the source of infection. PCR-based method is helpful in confirming diagnosis of PKDL, which is not applicable at field level. A referral laboratory at district or state level can be a solution to the problem. Since PKDL cases do not have a fatal outcome, treatment administration of these cases can be deferred until confirmed results are obtained, which requires about 7 days’ time. The detection of leishmanial DNA in skin lesions during successive treatment courses is essential to establish whether/ when PKDL patients are parasite free during/after treatment and to determine which PKDL patients need treatment for a longer period.

Changing trends in the epidemiology, clinical presentation, and diagnosis of Leishmania-HIV co-infection in India

Following the HIV epidemic, several countries have reported co-infections of Leishmania with HIV. Co-infection with these two pathogens results in rapid disease progression, more severe disease, and a poor response to treatment. A systematic review of the literature from India is presented herein. Since the first case of visceral leishmaniasis (VL) and HIV was published from India in 1999, a number of cases of HIV-Leishmania co-infection have been reported, but the proportion has been low (0.029-0.4%), as also reported in other countries where these two diseases are co-endemic. More than 89 cases of VL-HIV and 10 cases of cutaneous leishmaniasis (CL)-HIV have been published since 1999. Of these latter 10 cases, five had simple CL and five cases manifested with diffuse cutaneous leishmaniasis (DCL). In addition, one case of post-kala-azar mucocutaneous leishmaniasis in a patient with full-blown AIDS has also been reported. In two cases, it could not be ascertained whether they were cases of DCL or post-kala-azar dermal leishmaniasis from the description. Although the first case of VL-HIV co-infection was reported from the sub-Himalayan state of Uttarakhand, most cases have been reported from the VL endemic state of Bihar. HIV-Leishmania is not alarmingly high in India. Most cases were found to have occurred during 1997-2007. After that, the number of new cases decreased. This is most probably due to the low prevalence of HIV in VL and CL endemic regions and to the free supply of highly active antiretroviral therapy for HIV-infected patients.

Comparative evaluation of PCR and imprint smear microscopy analyses of skin biopsy specimens in diagnosis of macular, papular, and mixed papulo-nodular lesions of post-kala-azar dermal leishmaniasis

Diagnosis of post-kala-azar dermal leishmaniasis (PKDL), particularly the macular form, is difficult when based on microscopy. This study compared the results of nested PCR (91.9% positive samples) with imprint smear microscopy (70.9% positive samples) for 62 PKDL samples. We found that nested PCR, which indicated 87.5% positivity for the macular lesions, compared to 41.6% positivity by imprint smear microscopy, is an efficient method for early diagnosis of PKDL.

An approach for interlaboratory comparison of conventional and real-time PCR assays for diagnosis of human leishmaniasis

Protozoa of the Leishmania genus are transmitted to humans by the bite of infected sandflies, and are the causative agents of leishmaniasis which ranges from cutaneous to visceral clinical forms. The definitive diagnosis of leishmaniasis has relied traditionally on parasite demonstration, either by microscopy or culture; in the last years, diagnosis based on PCR methods has overcome some drawbacks of traditional methods, increasing sensitivity and allowing using less invasive sampling for diagnosis. However, there are not defined protocols and almost each laboratory applies its own in-house method. Although there are several studies comparing the performance of different methods within the same laboratory, those addressing interlaboratory comparison are scarce, in spite of the growing number of collaborative projects between partners from different leishmaniasis endemic and non-endemic countries. In this work we propose a protocol for interlaboratory comparison of conventional and real-time PCR methods involving four participant laboratories from four different endemic regions in four continents; the protocol includes a quality control step and reduces the variability among the samples tested by each participant. A panel of 77 samples from human origin and 9 from different parasite strains was blindly tested by the participants, aiming to assess the sensitivity of the different methods as well as their usefulness for species identification. Real-time PCR methods targeting the kDNA minicircles returned the highest sensitivity, while both PCR targeting ITS-1 and further HaeIII digestion and a combined algorithm including hsp70 PCR and restriction fragment length polymorphism analysis were the most appropriate approaches for species identification.

Application of loop-mediated isothermal amplification assay for the sensitive and rapid diagnosis of visceral leishmaniasis and post-kala-azar dermal leishmaniasis

Loop-mediated isothermal amplification (LAMP) is at the forefront in the search for innovative diagnostics for rapid and specific amplification of target DNA under isothermal conditions. We have applied LAMP assay using SYBR Green for clear-cut naked eye detection of Leishmania (Leishmania) donovani in 200 clinical samples of visceral leishmaniasis (VL) and post-kala-azar dermal leishmaniasis (PKDL). The assay was positive in 53/55 VL blood samples (sensitivity, 96.4%; 95% confidence interval [CI], 87.7-99%), 15/15 VL bone marrow aspirate samples (sensitivity, 100%; 95% CI, 79.6-100%), 60/62 PKDL tissue biopsy samples (sensitivity, 96.8%; 95% CI, 88.9-99.1%), and 1/68 control samples (specificity, 98.5%; 95% CI, 92.1-99.7%). The assay was specific for L. (L.) donovani, the causative species for VL and negative for L. (L.) infantum, L. (L.) tropica, and L. (L.) major. This is the first comprehensive clinical study demonstrating the applicability of the LAMP assay for a rapid and reliable molecular diagnosis of VL and PKDL.

Reliable diagnosis of post-kala-azar dermal leishmaniasis (PKDL) using slit aspirate specimen to avoid invasive sampling procedures

OBJECTIVE

Confirmatory diagnosis of post-kala-azar dermal leishmaniasis (PKDL) is primarily based on invasive skin biopsy procedure. We evaluated the utility of minimally invasive slit aspirate specimen for serological and molecular diagnosis of PKDL. We compared the PKDL diagnosis using slit aspirate and skin biopsy specimens from the same patients.

METHODS

Serological diagnosis using rK39 strip test was performed with serum and slit aspirate sample; molecular diagnosis for parasite detection and quantification was carried out by quantitative real-time PCR (Q-PCR) with skin biopsy and slit aspirate sample.

RESULTS

The rK39 serological strip test was positive in all PKDL cases with both slit aspirate and serum samples (n = 50) and negative in all control cases (n = 24), giving a sensitivity of 100% (95% CI: 92.9-100%) and a specificity of 100% (95% CI: 86.2-100%). Quantitative-PCR detected parasite in all PKDL slit aspirates (n = 50, sensitivity = 100%, 95% CI: 92.9-100%) and tissue biopsies (n = 46, sensitivity = 100%, 95% CI: 92.3-100; it was negative in all controls including dermal tissues (n = 24) and slit aspirates (n = 24), giving specificity of 100% (95% CI: 86.2-100%). The parasite load in tissue and slit aspirate samples was significantly (P < 0.0001) correlated (r = 0.82).

CONCLUSIONS

Slit aspirates are a simpler and minimally invasive sampling technique for initial screening by serology followed by confirmatory diagnosis of PKDL with microscopy and/or Q-PCR. The simplified procedure has the potential for epidemiological studies and assessment of cure in PKDL.

PCR-based detection of Leishmania DNA in skin samples of post kala-azar dermal leishmaniasis patients from an endemic area of Bangladesh

Post kala-azar dermal leishmaniasis (PKDL) is a sequel of visceral leishmaniasis (VL) and PKDL patients are an important reservoir for anthroponotic transmission of VL. Therefore, diagnosis and treatment of PKDL is important for the kala-azar elimination program in South Asia, including Bangladesh. While definitive diagnosis of PKDL is still based on microscopy, despite the low sensitivity of this method of diagnosis, PCR for identification of kinetoplast DNA (kDNA) from Leishmania parasites is expected to be a rapid and sensitive diagnostic method. We attempted PCR-based diagnosis from skin biopsy specimens and compared PCR to other available detection methods in order to determine the acceptability and feasibility of the PCR diagnostic method in an endemic area of VL in Bangladesh. Both skin biopsy specimens and blood samples were collected from 110 patients suspected to have PKDL from 6 subdistrict health complexes in Mymensingh, Bangladesh. Using microscopy, we identified 32 samples (29.1%) that were positive for Leishmania. Immunochromatography tests indicated that 85 samples (77.3%) were positive for Leishmania. In contrast, a total of 104 (94.5%) samples tested positive using nested PCR, while unaffected portions of skin from PKDL patients tested negative. Sequencing analysis of the PCR products indicated that the amplified portion had more than 98% nucleotide sequence identity to the Leishmania donovani reference strain, D10. These findings indicate that the PCR method using a skin biopsy is highly sensitive and useful for confirmatory diagnosis of PKDL.

Post-kala-azar dermal leishmaniasis: recent developments

A substantial number of patients who recover from kala-azar will develop dermatosis [commonly known as post-kala-azar dermal leishmaniasis (PKDL)]. It usually occurs in the Indian subcontinent and East Africa. As many as 10-20% of Indian cases and 50-60% of Sudanese cases develop PKDL after successful treatment of visceral leishmaniasis. Most cases occur after infection with Leishmania donovani and less commonly after Leishmania infantum. However, the PKDL is extremely rare in patients infected with Leishmania chagasi. Though exact pathology is not yet fully known, here we review various evidence, which suggest that the pathogenesis is largely immunologically mediated. Our group has been of the opinion that PKDL disease manifestation is a result of in-vivo generation of quasi-species either as in-vivo hybridization of various circulating and latent populations of the causative species within the host cells or due to external reinfection. We, and other scientists, have recently demonstrated that strains of Leishmania that cause visceral diseases differ genetically from those that cause PKDL. We feel that this review will incite interest in several parasitologists and molecular biologists in the pathogenesis of this important manifestation of the infection, often blamed as the source of outbreaks of leishmaniasis.

[Choice of primers: a determining element in molecular diagnosis of cutaneous leishmaniasis]

The cutaneous leishmaniasis (CL) is a parasitic disease which represents a serious problem for the public health not only in Tunisia but also all over the world. Its diagnosis is based on the techniques which are usually used, direct examination and in vitro culture. Because of several factors, these techniques lack sensitivity. The molecular biology, which is indeed more rapid and more sensitive, has proved its effectiveness in diagnosis of the CL. There are two main aims for our research work. First, to show the contribution of the Polymerase Chain Reaction (PCR) during the diagnosis of CL (of course by comparing the results obtained when using this technique with those found through the direct examination); second, to compare the two pairs of primers which amplify the leishmanien gene coding for the 18s ribosomal sub-unit: the pair R221/R332 (PCR1) and the pair Lei70L/Lei70R (PCR2). Our work was carried out upon 299 samples. One hundred and eighty-eight of them were positive using the direct examination and/or the PCR and 111 were negative. Only two samples were positive using of course the direct examination in comparison with 74 which were positive when using only the PCR (PCR1 and/or PCR2). Among these 74 samples, 64 where positive using only PCR2 in comparison with two samples which were positive using only PCR1. The eight remaining samples were at once positive for the PCR1 and the PCR2. The PCR (notably the PCR2) has proved a more significant percentage of positivity in comparison with direct examination: 98.98% for the PCR and 60.6% for direct examination.

Applications of molecular methods for Leishmania control

This article reviews the recent advances made in the field of human leishmaniasis. Special emphasis is placed upon the application of various molecular tools for accurate and rapid diagnosis, understanding the mechanisms of drug resistance and identification of vaccine candidates. The focus will be on the major role played by recombinant antigens in the immunoserodiagnosis and progress of the Leishmania genome project, which has enabled researchers to design better PCR primers and molecular probes for microarrays. A special interest is placed on the recombinant antigen (rK39) cloned from the Leishmania chagasi kinesin gene and a very recently cloned recombinant antigen (KE16) from the Old World Leishmania donovani species with high sensitivity and specificity. Advances made in the specific PCR primer designed to diagnose and differentiate various species and strains of Leishmania causing visceral and post-kala-azar-dermal leishmaniasis have been covered. Molecular methods (e.g., DNA and protein microarrays) applied to understanding the pathobiology of the parasite, mechanism of host invasion, drug interaction and drug resistance to develop effective therapeutic molecules, gene expression profiling studies that have opened doors to understand many host-parasite relations, effective therapy and vaccine candidates are extensively covered in this review.