Detection of asymptomatic Leishmania infection in Bangladesh by novel antigen and antibody diagnostic tools shows strong association with PKDL patients

Abstract

Background: Asymptomatic Leishmania infections outnumber clinical infections on the Indian sub-continent (ISC) where disease reservoirs are anthroponotic. Diagnostics which detect active asymptomatic infection, which are suitable for monitoring and surveillance, may be of benefit to the visceral leishmaniasis (VL) elimination campaign on the ISC. Methodology/Principal Findings: Quantitative polymerase chain reaction (qPCR), loop mediated isothermal amplification (LAMP), the direct agglutination test (DAT), and the Leishmania antigen ELISA were carried out on blood and urine samples collected from 720 household and neighbouring contacts of 276 VL and post kala-azar dermal leishmaniasis (PKDL) index cases, with no symptoms or history of VL and PKDL, in endemic regions of Bangladesh between September 2016 and March 2018. Of the 720 contacts of index cases, asymptomatic infection was detected in 69 (9.6%) participants by a combination of qPCR (1.0%), LAMP (2.1%), DAT (3.9%), and Leishmania antigen ELISA (3.3%). Only 1 (0.1%) participant was detected positive by all 4 diagnostic tests. Poor agreement between tests was calculated using Cohen's kappa statistics, however the Leishmania antigen ELISA and DAT in combination capture all participants positive by more than one test. We find strong evidence for association between the index case being a PKDL case (OR 1.94, p = 0.009), specifically macular PKDL (OR 2.12, p = 0.004) and being positive for at least one of the four tests. Conclusions/Significance: Leishmania antigen ELISA detects active asymptomatic infection, requires a non-invasive sample, and therefore may be of benefit for monitoring transmission and surveillance in an elimination setting in combination with serology. Development of an antigen detection test in RDT format would be of benefit to the elimination campaign.

Evaluation of Loopamp™ Leishmania Detection Kit and Leishmania Antigen ELISA for Post-Elimination Detection and Management of Visceral Leishmaniasis in Bangladesh

“…The Leishmania antigen ELISA in contrast is more compatible for surveillance studies as another sensitive, cost-effective, high-throughput, and non-invasive diagnostic tool, offering sampling feasibility and increased patient compliance ( Abeijon and Campos-Neto, 2013 ). The prospect of the assay to identify asymptomatic carriers from a cohort is explored in a recent study with promising outcome ( Owen et al., 2021 ). Its unique quantification feature can also be exploited to determine treatment outcome.…”

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“…Laboratory diagnosis of Leishmaniasis can be made by 1) Demonstration of parasite, 2) Serological tests e.g., rK39 strip test and direct agglutination test, 3) Antigen detection, 4) Molecular diagnosis, 5) Leishmania skin test (LST) or Montenegro skin test, 6) Lymphocyte proliferation assay (LPA), 7) Western blot, 8) Isoenzyme analysis, 9) Excreted factor, 10) DNA based methods, 11) Polymerase Chain Reaction (PCR), 12) Single Nucletide polymorphism (SNP), 13) IgG1potential biomarker of post chemotherapeutic relapse diagnostic test, 14) Immunochromatographic rapid diagnostic tests for visceral leishmaniasis (Mann et al, 2021;Priyamvada et al, 2021;Mondal et al, 2016;Adams et al, 2018;Vallur et al, 2015;Bhattacharyya et al, 2014;Kumar et al, 2020aKumar et al, , 2020bChappuis et al, 2007;Cunningham et al, 2012;Boelaert et al, 2008;Rijal et al, 2019). In another major development, Leishmania antigen ELISA on urine detects active asymptomatic infection, requires a non-invasive sample (Owen et al, 2021). Therefore, this test may be of benefit for monitoring transmission and surveillance in an elimination setting in combination with serology (Owen et al, 2021).…”

“…In another major development, Leishmania antigen ELISA on urine detects active asymptomatic infection, requires a non-invasive sample (Owen et al, 2021). Therefore, this test may be of benefit for monitoring transmission and surveillance in an elimination setting in combination with serology (Owen et al, 2021). Development of an antigen detection test in a rapid diagnostic test (RDT) format would be of benefit to the elimination campaign (Owen et al, 2021).…”

“…Therefore, this test may be of benefit for monitoring transmission and surveillance in an elimination setting in combination with serology (Owen et al, 2021). Development of an antigen detection test in a rapid diagnostic test (RDT) format would be of benefit to the elimination campaign (Owen et al, 2021).…”