Abstract
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.
Highlights
IntroductionAn estimated 50,000 to 90,000 new cases of kala-azar or Visceral Leishmaniasis (VL), caused by the parasite Leishmania donovani occur annually, with the contribution of Bangladesh, India, and Nepal being around 67% (https://www.who.int/news-room/fact-sheets/detail/ Leishmaniasis last accessed on 4th December, 2020)
Worldwide, an estimated 50,000 to 90,000 new cases of kala-azar or Visceral Leishmaniasis (VL), caused by the parasite Leishmania donovani occur annually, with the contribution of Bangladesh, India, and Nepal being around 67%
The primary literature search identified 264 studies for which the titles were screened and assessed for relevance based on key words “(((Leishmaniasis-[title]) or Kala -azar[title]) or Post Kala-azar Dermal Leishmaniasis (PKDL) [title]) and (((((((((biomarker) or biomarkers) or marker) or diagnosis) or markers) or level) or levels) or concentration) or activity) or profile) or PCR) or quantitative PCR (qPCR))”, Figure 1
Summary
An estimated 50,000 to 90,000 new cases of kala-azar or Visceral Leishmaniasis (VL), caused by the parasite Leishmania donovani occur annually, with the contribution of Bangladesh, India, and Nepal being around 67% (https://www.who.int/news-room/fact-sheets/detail/ Leishmaniasis last accessed on 4th December, 2020). The Kala Azar Elimination Programme (KAEP) consists of four consecutive phases and began with a “preparatory phase” which involved development/review of national policy, strategic and advocacy plans, operational plans to implement the national plan for elimination, development, and adoption of technical guidelines (Sundar et al, 2018) This was followed by a multiprolonged “attack phase” that included integrated vector management with indoor residual spraying for 5 years in affected areas along with active surveillance, early diagnosis and complete treatment. The number of VL cases in India, Nepal, and Bangladesh have declined steadily from over 77,000 reported cases in 1992 to fewer than 7,000 cases in 2016 (Rijal et al, 2019) and further reduced to 3,128 in 2019 (World Health Organization, 2020)
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