Modeling post-kala-azar dermal leishmaniasis as an infection reservoir for visceral leishmaniasis

Abstract

Visceral Leishmaniasis (VL) is a potentially fatal disease caused by the protozoan parasite Leishmania donovani. This disease is a health problem for the very poor because it results in thousands of deaths and illnesses every year. Some countries, such as India and Bangladesh, have started programs to reduce the occurrences of VL by focusing on early diagnosis and complete treatment of VL. Post-Kala-azar Dermal Leishmaniasis (PKDL) is a cutaneous manifestation of Leishmaniasis that can occur following the incomplete treatment of VL. Diagnosis and treatment of PKDL are limited in affected regions, and PKDL has been identified as a possible reservoir for infection. This study develops a mathematical model of the relationship between the level of PKDL treatment and the incidences of VL during a given period. The results indicate a nearly linear relationship between PKDL treatment rates and the percent reduction of VL incidences. With the current treatments available and considering achievable levels of treatment, the model predicts that up to 20% of VL cases could be prevented by treating new PKDL cases. Hypothetical combined treatment initiatives including bed nets and insecticide spraying are also considered. Results suggest that the population of individuals with PKDL is certainly a significant factor in the transmission of L. donovani infection, with treatment of new cases particularly important.