Post-Kala-Azar Dermal Leishmaniasis as a Reservoir for Visceral Leishmaniasis Transmission

Abstract

Post-kala-azar dermal leishmaniasis (PKDL) is a parasitic skin infection which can occur after visceral leishmaniasis (VL). Recent xenodiagnosis studies (Mondal et al., Clin. Infect. Dis., 2018) have uncovered the infectiousness of PKDL. When including this in a transmission model, PKDL cases appear as an important reservoir of infection, likely frustrating the VL elimination efforts on the Indian subcontinent.

Keywords: elimination; post-kala-azar dermal leishmaniasis (PKDL); transmission dynamics; visceral leishmaniasis; xenodiagnosis.

Figure 1

Visceral Leishmaniasis (VL) Incidence Curves during Interventions and the Corresponding Change in Relative Contribution to Transmission of Different Infection and Disease Stages during the WHO Strategy. The precontrol VL incidence (year –2–0) in a high-endemic setting (10/10 000/year) is followed by 5 years of interventions in the WHO active phase (years 0–5) and then 10 years of interventions in the WHO consolidation phase (years 5–15). The dashed lines represent the incidence curves for which the regular WHO strategy is combined with the post-kala-azar dermal leishmaniasis (PKDL) control strategy (years 0–15). The black horizontal dashed line depicts the 1/10 000/year target of elimination as a public health problem. In Model E0 only symptomatic individuals with VL and PKDL contribute to transmission; in Model E1, asymptomatic individuals also contribute to transmission. The early asymptomatic stage represents individuals that are PCR-positive and negative in the direct agglutination test (DAT); the late asymptomatic stage represents individuals that are PCR-positive and DAT-positive (as fitted to the KalaNet dataset, India [9]). Late-asymptomatic individuals are considered to be twice as infectious compared with early-asymptomatic individuals . A small percentage of late-asymptomatic individuals become symptomatic, after which most receive first-line treatment. In case of treatment failure, a second-line treatment is administered. Individuals in the treatment stages are considered half as infectious compared with those in the symptomatic untreated stage . Further information about the models is presented in .