Quantitative PCR in Epidemiology for Early Detection of Visceral Leishmaniasis Cases in India

Abstract

IntroductionStudies employing serological, DTH or conventional PCR techniques suggest a vast proportion of Leishmania infected individuals living in regions endemic for Visceral Leishmaniasis (VL) remain asymptomatic. This study was designed to assess whether quantitative PCR (qPCR) can be used for detection of asymptomatic or early Leishmania donovani infection and as a predictor of progression to symptomatic disease.MethodsThe study included 1469 healthy individuals living in endemic region (EHC) including both serology-positive and -negative subjects. TaqMan based qPCR assay was done on peripheral blood of each subject using kDNA specific primers and probes.ResultsA large proportion of EHC 511/1469 (34.78%) showed qPCR positivity and 56 (3.81% of 1469 subjects) had more than 1 calculated parasite genome/ml of blood. However, the number of individuals with parasite load above 5 genomes/ml was only 20 (1.36% of 1469). There was poor agreement between serological testing and qPCR (k = 0.1303), and 42.89% and 31.83% EHC were qPCR positive in seropositive and seronegative groups, respectively. Ten subjects had developed to symptomatic VL after 12 month of their follow up examination, of which eight were initially positive according to qPCR and among these, five had high parasite load.DiscussionThus, qPCR can help us to detect significant early parasitaemia, thereby assisting us in recognition of potential progressors to clinical disease. This test could facilitate early intervention, decreased morbidity and mortality, and possibly interruption of disease transmission.

Leishmania vaccine development: exploiting the host–vector–parasite interface

“…Demonstrating prevention of infection may be possible in areas with high rates of transmission, but will require surveillance with sensitive and specific tools to monitor asymptomatic infection and progression from negative to positive during one or more transmission seasons (69, 70). Although effective VL diagnostics for detecting disease have been widely available for years (71–76), only recently has the promise of sensitive and specific tools for monitoring early and low level infection been demonstrated (77).…”

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

“…Several PCR protocols have been developed for detection of Leishmania parasite, such as triplex PCR [16], multiplex PCR [17], restriction fragment length polymorphism (RFLP) analysis and nested PCR [18]. Quantitative Real-time PCR (Q-PCR) has emerged as a highly sensitive tool for VL and PKDL diagnosis with simultaneous quantification of the parasite burden [19–22]. However, these assays are not used for routine diagnosis of Leishmania infection as these require of well equipped laboratory facilities along with technical expertise.…”

Causes and consequences of higher Leishmania infantum burden in patients with kala‐azar: a study of 625 patients

“…By studying the factors associated with the parasite burden, critical clues regarding the manner in which infection by Leishmania could be controlled may be obtained (as a product of both parasite and host factors). Thus, the parasite burden could eventually serve as an alert regarding progression from infection to disease and could be used at the community level [14][15][16][17]. The parasite burden may also be used during follow-up of immunosuppressed patients as a marker of treatment success [13,[18][19][20][21][22].…”