Typical and atypical cutaneous leishmaniasis in Himachal Pradesh (India)

Salivary antigens rPagSP02 and rPagSP06 are a reliable composite biomarker for evaluating exposure to Phlebotomus argentipes in Sri Lanka

Phlebotomus argentipes is the established vector of leishmaniasis in the Indian sub-continent. Antibodies to sand fly salivary antigens are biomarkers for vector-host exposure in leishmaniasis-endemic regions. Ph. argentipes transmits Leishmania donovani in Sri Lanka, primarily causing cutaneous leishmaniasis (CL). Our study compared the performance of salivary gland homogenate (SGH) from a lab-reared local strain of Ph. argentipes females to a composite recombinant salivary biomarker (rPagSP02 + rPagSP06) in a CL-endemic population. Sera from 546 healthy individuals, 30 CL patients, and 15 non-endemic individuals were collected. Western blot analysis of Ph. argentipes SGH identified immunogenic bands between 15 kDa and 67 kDa, with bands of predicted molecular weight ∼of 15 kDa (SP02) and ∼28-30 kDa (SP06) as the major antibody targets. Indirect ELISAs using SGH or rPagSP02 + rPagSP06 antigens showed high sensitivity (96.7%) and specificity (100%), detecting comparable seropositivity in endemic populations. rPagSP02 + rPagSP06 exhibited enhanced discriminatory ability, supported by a strong positive correlation (r = 0.869) with SGH. Our findings indicate that the composite rPagSP02 + rPagSP06 salivary biomarker effectively identifies Ph. argentipes exposure in individuals living in Sri Lanka, showing promising potential for use in surveillance. These findings should be further validated to confirm the epidemiological applications in leishmaniasis-endemic regions.

Assessment of High-Resolution Melting Curve Analysis for Leishmania spp. Detection in Different Clinical Manifestations of Leishmaniasis in India

The accurate diagnosis and identification of Leishmania species are crucial for the therapeutic selection and effective treatment of leishmaniasis. This study aims to develop and evaluate the use of high-resolution melting curve analysis (HRM)-PCR for Leishmania species identification causing visceral leishmaniasis (VL), post-kala-azar dermal leishmaniasis (PKDL) and cutaneous leishmaniasis (CL) in the Indian subcontinent. Two multi-copy targets (ITS-1 and 7SL-RNA genes) were selected, and an HRM-PCR assay was established using L. donovani, L. major, and L. tropica standard strain DNA. The assay was applied on 93 clinical samples with confirmed Leishmania infection, including VL (n = 30), PKDL (n = 50), and CL (n = 13) cases. The ITS-1 HRM-PCR assay detected as little as 0.01 pg of template DNA for L. major and up to 0.1 pg for L. donovani and L. tropica. The detection limit for the 7SL-RNA HRM-PCR was 1 pg for L. major and 10 pg for L. donovani and L. tropica. The ITS-1 HRM-PCR identified 68 out of 93 (73.11%) leishmaniasis cases, whereas 7SL-RNA HRM-PCR could only detect 18 out of 93 (19.35%) cases. A significant correlation was observed between the kDNA-based low Ct values and ITS-1 HRM-PCR positivity in the VL (p = 0.007), PKDL (p = 0.0002), and CL (p = 0.03) samples. The ITS-1 HRM-PCR assay could identify Leishmania spp. causing different clinical forms of leishmaniasis in the Indian subcontinent, providing rapid and accurate results that can guide clinical management and treatment decisions.

rPagSP02+rPagSP06 recombinant salivary antigen is a reliable biomarker for evaluating exposure to Phlebotomus argentipes in Sri Lanka

Phlebotomus argentipes is the established vector of leishmaniasis in the Indian sub-continent. Antibodies to sand fly salivary antigens are biomarkers for vector-host exposure in leishmaniasis-endemic regions. Ph. argentipes transmits Leishmania donovani in Sri Lanka, primarily causing cutaneous leishmaniasis (CL). Our study compared the performance of salivary gland homogenate (SGH) from a lab-reared local strain of Ph. argentipes females to a composite recombinant salivary biomarker (rPagSP02 + rPagSP06) in a CL-endemic population. Sera from 546 healthy individuals, 30 CL patients, and 15 non-endemic individuals were collected. Western blot analysis of Ph. argentipes SGH identified immunogenic bands between 15 kDa and 67 kDa, with bands of predicted molecular weight õf 15 kDa (SP02) and ~28-30 kDa (SP06) as the major antibody targets. Indirect ELISAs using SGH or rPagSP02 + rPagSP06 antigens showed high sensitivity (96.7%) and specificity (100%), detecting comparable seropositivity in endemic populations. rPagSP02 + rPagSP06 exhibited enhanced discriminatory ability, supported by a strong positive correlation (r = 0.869) with SGH. Our findings indicate that the composite rPagSP02 + rPagSP06 salivary biomarker effectively identifies Ph. argentipes exposure in individuals living in Sri Lanka, showing promising potential for use in surveillance. These findings should be further validated to confirm the epidemiological applications in leishmaniasis-endemic regions.

Comparative Analysis of Phlebotomus argentipes Vector of Leishmaniasis in India and Sri Lanka

Phlebotomus argentipes is the predominant sandfly vector of leishmaniasis in the Indian subcontinent. India and Sri Lanka primarily report visceral and cutaneous leishmaniasis caused by Leishmania donovani. We compared Ph. argentipes from two locations, focusing on its morphological, molecular, and salivary protein characteristics. Sandflies were captured using CDC light traps and cattle-baited net traps. Species identification and morphological comparisons were carried out using standard taxonomic keys. DNA extracted from 12 Sri Lankan sandfly samples was PCR-amplified and sequenced for the variable region of Cytochrome oxidase subunit I. Existing DNA sequences of India from GenBank were utilized for a phylogenetic analysis between Sri Lanka and India. Salivary protein profiles were studied using SDS-PAGE, Western blot, and electrospray ionization/LC/MS/MS. The morphological similarities observed between female Ph. argentipes from India and Sri Lanka suggest the presence of Ph. argentipes var. glaucus. A phylogenetic analysis showed genetic divergence between Ph. argentipes populations, but both shared a similar salivary protein profile. A common, strong 30 kDa immunogenic band comprised PagSP05, PagSP06, and PagSP17 proteins of Ph. argentipes. The similarity between the immunogenic salivary proteins suggests their potential use as common markers for vector exposure or immune response stimulants across regions. The use of multiple samples for each category of serum would improve the comprehensiveness of the immunogenic profiles obtained.

Detection of Internal Transcribed Spacer 1 and hsp70 Genetic Markers Using Restriction Fragment Length Polymorphisms and Sequencing in Identification of Leishmania Species Causing Tegumentary Leishmaniasis in Brazil

The identification of Leishmania species that cause tegumentary leishmaniasis (TL) is important for taxonomic and prognostic purposes. Molecular analysis using different Leishmania genomic targets is the most useful method for identifying Leishmania species. Therefore, we evaluated the performance of ribosomal RNA internal transcribed spacer 1 (ITS1) and heat shock protein (hsp70) genetic markers by polymerase chain reaction (PCR), followed by restriction fragment length polymorphism analysis (RFLP) and sequencing, for identification of Leishmania species. Samples from 84 Brazilian patients were amplified. Internal transcribed spacer 1 PCR followed by RFLP (HaeIII) [ITS1-RFLP (HaeIII)] identified 46.4% (39/84) of the samples as compatible with the Viannia subgenus. Internal transcribed spacer 1 PCR followed by sequencing (ITS1-sequencing) identified Leishmania (Viannia) braziliensis in 91.7% (77/84) of the TL samples, Leishmania (Leishmania) amazonensis in 3.6% (3/84), L. (V.) guyanensis in 2.4% (2/84), and L. (L.) infantum in 1.2% (1/84). One of the samples showed the same proportion of similarity with L. (V.) guyanensis and L. (V.) panamensis. hsp70 nested PCR followed by RFLP (HaeIII) [nested hsp70-RFLP (HaeIII)] identified 91.7% (77/84) of the samples as compatible with L. (V.) braziliensis/L. (V.) naiffi, 3.6% (3/84) with L. (L.) amazonensis, 1.2% (1/84) with L. (L.) infantum, and 3.6% (3/84) with L. (V.) guyanensis. hsp70 PCR followed by sequencing (hsp70-sequencing) identified L. (V.) braziliensis in 91.7% (77/84) of the TL samples, L. (L.) amazonensis in 3.6% (3/84), L. (V.) guyanensis in 3.6% (3/84), and L. (L.) infantum in 1.2% (1/84). Our findings clearly showed that nested hsp70-RFLP (HaeIII) is better than ITS1-RFLP (HaeIII) and that ITS1 or hsp70 PCR followed by sequencing was adequate for identifying Leishmania species. We also found that Leishmania (Viannia) braziliensis is the most common species causing TL in Brazil. Therefore, sequencing multiple target genes such as ITS1 and hsp 70 is more accurate than RFLP for identifying Leishmania species.

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.

Leishmania donovani persistence and circulation causing cutaneous leishmaniasis in unusual-foci of Nepal

Cutaneous leishmaniasis cases have increased dramatically in recent years in Nepal. The study offers molecular identification of the Leishmania species using 40 patient's aspiration biopsy samples, targeting markers kinetoplast minicircle DNA (kDNA) and internal transcribed spacer-1 (ITS1). Among molecularly diagnosed 22 cutaneous leishmaniasis cases, L. donovani complex was identified in 13 instances and L. major in 9 cases. The ITS1 PCR was positive in 12 of the positive nested- kDNA PCR cases (12/22), confirming L. donovani complex in seven of the cases and L. major in five of the cases. In addition, the study conclude that concurrent occurrence of atypical cutaneous infections caused by L. donovani parasite in 59.1% of cases and typical cutaneous infections caused by L. major parasite in 40.9% of cases. A Phylogentic analaysis showed that the detected L. donovani species present null genetic distances from seven references of L. donovani, but slight differences between ITS1 sequences and not grouped into a significant monophyletic cluster.

Detection of Leishmania donovani in Wild-Caught Phlebotomine Sand Flies in Endemic Focus of Leishmaniasis in Himachal Pradesh, India

An endemic focus of cutaneous leishmaniasis (CL) is located in the Sutlej River Valley in Himachal Pradesh (India) in the north-western Himalaya where CL co-exists with visceral leishmaniasis (VL). In areas of the Indian subcontinent such as Rajasthan, cutaneous leishmaniasis is transmitted by Phlebotomus papatasi (Scopoli) and Phlebotomus salehi. In Himachal Pradesh, Phlebotomus longiductus (Parrot) is suspected to be the vector for CL. In the current study, sand flies were collected and tested for Leishmania infection and to confirm the vector species causing CL. Sand flies were collected during April and September of 2017-2019 from CL endemic villages of Rampur (Shimla), Nirmand (Kullu) and Nichar (Kinnaur) districts of Himachal Pradesh. The sand flies were identified as Phlebotomus (adlerius) longiductus (Parrot) and Phlebotomus (larrousisus) major (Annandale). The density of P. longiductus was found highest. The elevation of villages ranged from 947 m to 2,130 m and were far from the presence of subsoil water. Field collected sand flies tested positive (7.69%) for Leishmania donovani by PCR-RFLP. The L. donovani sequences detected from P. longiductus were 97% similar to L. donovani sequences reported from the cases of CL in Himachal Pradesh.The Leishmania positive sand flies were morphologically identified as Phlebotomus adlerious longiductus providing one step further evidence towards the vector status of CL in Himachal Pradesh. The findings of the study are of epidemiological significance for strategic planning of vector control for leishmaniasis in India.