Epidemiology of Leishmaniasis in the Time of Drug Resistance

Abstract

The epidemiology of leishmaniasis is dynamic, and the disease is (re-)emerging and spreading in many regions. The control of leishmaniasis is mainly challenged by three major escalating risk factors: human-made and environmental changes, immune status (essentially because of Leishmania/HIV co-infection), and treatment failure and drug resistance. The epidemiology of drug resistance is very much codetermined by other factors that threaten control of the disease. Risk factors often vary from region to region, and further interact reciprocally and synergistically, thus each time defining a regional characteristic epidemiological challenge. Consequently, drug resistance should always be studied, perceived, and presented in the specific epidemiological and clinical context of the studied endemic region. In the present chapter, an update of various aspects of the leishmaniasis epidemiology will be presented, with a particular emphasis on their relation with parasite drug resistance. The focus of this chapter is on antimonials since we have most experience in the field and in the lab with them. Although these drugs are currently being abandoned as first-line treatment in the Indian subcontinent, we can still draw many lessons from the experience with antimonials with respect to (1) speculation of the future of the few additional available drugs and (2) the design and implementation of adequate surveillance strategies to monitor their efficacy. Major gaps and confusing issues currently existing in our epidemiological knowledge of drug resistance will be addressed, with a particular attention for the ambiguous interpretation of the concepts of drug resistance and treatment failure. Existing and needed tools relevant for epidemiological surveillance (at the levels of primary health centers, reference hospitals, and laboratories) and the potential impact of this surveillance on local drug policies will be reviewed as a guide to orient further research activities and inspire funding agencies.